diff --git a/toolchain/lower/file_context.cpp b/toolchain/lower/file_context.cpp
index 52dbcd0bac01..55236741d7ce 100644
--- a/toolchain/lower/file_context.cpp
+++ b/toolchain/lower/file_context.cpp
@@ -372,10 +372,13 @@ auto FileContext::BuildDISubprogram(const SemIR::Function& function,
   auto loc = converter_.ConvertLoc(
       function.definition_id,
       [](DiagnosticLoc, const Internal::DiagnosticBase<>&) {});
-  // FIXME: Add more details here, including mangled name, real subroutine type
-  // (once type information is built), etc.
+  auto name = sem_ir().names().GetAsStringIfIdentifier(function.name_id);
+  CARBON_CHECK(name) << "Unexpected special name for function: "
+                     << function.name_id;
+  // FIXME: Add more details here, including real subroutine type (once type
+  // information is built), etc.
   return di_builder_.createFunction(
-      di_compile_unit_, llvm_function->getName(), /*LinkageName=*/"",
+      di_compile_unit_, *name, llvm_function->getName(),
       /*File=*/di_builder_.createFile(loc.filename, ""),
       /*LineNo=*/loc.line_number,
       di_builder_.createSubroutineType(
diff --git a/toolchain/lower/testdata/alias/local.carbon b/toolchain/lower/testdata/alias/local.carbon
index 61de086705c9..df04a9ea44e0 100644
--- a/toolchain/lower/testdata/alias/local.carbon
+++ b/toolchain/lower/testdata/alias/local.carbon
@@ -32,7 +32,7 @@ fn F() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "local.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/array/array_in_place.carbon b/toolchain/lower/testdata/array/array_in_place.carbon
index 4f8f78057973..91432af7ba67 100644
--- a/toolchain/lower/testdata/array/array_in_place.carbon
+++ b/toolchain/lower/testdata/array/array_in_place.carbon
@@ -36,7 +36,7 @@ fn G() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "array_in_place.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/array/assign_return_value.carbon b/toolchain/lower/testdata/array/assign_return_value.carbon
index d5d87bf8dba0..b24670f0b6f0 100644
--- a/toolchain/lower/testdata/array/assign_return_value.carbon
+++ b/toolchain/lower/testdata/array/assign_return_value.carbon
@@ -55,12 +55,12 @@ fn Run() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "assign_return_value.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 31, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 11, column: 24, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 14, column: 7, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 14, column: 21, scope: !9)
 // CHECK:STDOUT: !12 = !DILocation(line: 13, column: 1, scope: !9)
diff --git a/toolchain/lower/testdata/array/base.carbon b/toolchain/lower/testdata/array/base.carbon
index 15295cd0c6d9..ddf6379c297f 100644
--- a/toolchain/lower/testdata/array/base.carbon
+++ b/toolchain/lower/testdata/array/base.carbon
@@ -76,7 +76,7 @@ fn Run() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "base.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/array/function_param.carbon b/toolchain/lower/testdata/array/function_param.carbon
index f92a9f73fc2b..76aac8284789 100644
--- a/toolchain/lower/testdata/array/function_param.carbon
+++ b/toolchain/lower/testdata/array/function_param.carbon
@@ -51,12 +51,12 @@ fn G() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "function_param.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 10, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 16, column: 12, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 16, column: 10, scope: !9)
 // CHECK:STDOUT: !12 = !DILocation(line: 16, column: 3, scope: !9)
diff --git a/toolchain/lower/testdata/basics/false_true.carbon b/toolchain/lower/testdata/basics/false_true.carbon
index 24061f904c4a..892dcbb604a8 100644
--- a/toolchain/lower/testdata/basics/false_true.carbon
+++ b/toolchain/lower/testdata/basics/false_true.carbon
@@ -36,9 +36,9 @@ fn T() -> bool {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "false_true.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "T", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "T", linkageName: "T", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 16, column: 3, scope: !8)
diff --git a/toolchain/lower/testdata/basics/int_types.carbon b/toolchain/lower/testdata/basics/int_types.carbon
index 0c32aeaff2ea..5c2cb942b8fc 100644
--- a/toolchain/lower/testdata/basics/int_types.carbon
+++ b/toolchain/lower/testdata/basics/int_types.carbon
@@ -43,13 +43,13 @@ fn F_u65536(a: u65536) -> u65536 { return a; }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "int_types.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F_i8", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F_i8", linkageName: "F_i8", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 24, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "F_u16", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "F_u16", linkageName: "F_u16", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 12, column: 27, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "F_i64", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "F_i64", linkageName: "F_i64", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 13, column: 27, scope: !10)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "F_u65536", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "F_u65536", linkageName: "F_u65536", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 14, column: 36, scope: !12)
diff --git a/toolchain/lower/testdata/basics/numeric_literals.carbon b/toolchain/lower/testdata/basics/numeric_literals.carbon
index 0f3e04b5b51a..a06a1e38aad3 100644
--- a/toolchain/lower/testdata/basics/numeric_literals.carbon
+++ b/toolchain/lower/testdata/basics/numeric_literals.carbon
@@ -67,7 +67,7 @@ fn F() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "numeric_literals.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/basics/type_values.carbon b/toolchain/lower/testdata/basics/type_values.carbon
index 4ae024e48969..e1e826b65aeb 100644
--- a/toolchain/lower/testdata/basics/type_values.carbon
+++ b/toolchain/lower/testdata/basics/type_values.carbon
@@ -50,11 +50,11 @@ fn F64() -> type {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "type_values.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "I32", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "I32", linkageName: "I32", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 15, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "I48", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "I48", linkageName: "I48", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 19, column: 3, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "F64", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "F64", linkageName: "F64", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 23, column: 3, scope: !10)
diff --git a/toolchain/lower/testdata/basics/zero.carbon b/toolchain/lower/testdata/basics/zero.carbon
index 69befd861785..f30827b032f4 100644
--- a/toolchain/lower/testdata/basics/zero.carbon
+++ b/toolchain/lower/testdata/basics/zero.carbon
@@ -27,7 +27,7 @@ fn Main() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "zero.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/builtins/float.carbon b/toolchain/lower/testdata/builtins/float.carbon
index 975caf051929..357ec1dcd1fd 100644
--- a/toolchain/lower/testdata/builtins/float.carbon
+++ b/toolchain/lower/testdata/builtins/float.carbon
@@ -117,38 +117,38 @@ fn TestGreaterEq(a: f64, b: f64) -> bool { return GreaterEq(a, b); }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "float.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestNegate", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestNegate", linkageName: "TestNegate", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 39, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 12, column: 32, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAdd", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAdd", linkageName: "TestAdd", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 15, column: 44, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 37, scope: !9)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "TestSub", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "TestSub", linkageName: "TestSub", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 18, column: 44, scope: !12)
 // CHECK:STDOUT: !14 = !DILocation(line: 18, column: 37, scope: !12)
-// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "TestMul", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "TestMul", linkageName: "TestMul", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !16 = !DILocation(line: 21, column: 44, scope: !15)
 // CHECK:STDOUT: !17 = !DILocation(line: 21, column: 37, scope: !15)
-// CHECK:STDOUT: !18 = distinct !DISubprogram(name: "TestDiv", scope: null, file: !3, line: 24, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !18 = distinct !DISubprogram(name: "TestDiv", linkageName: "TestDiv", scope: null, file: !3, line: 24, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !19 = !DILocation(line: 24, column: 44, scope: !18)
 // CHECK:STDOUT: !20 = !DILocation(line: 24, column: 37, scope: !18)
-// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "TestEq", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "TestEq", linkageName: "TestEq", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !22 = !DILocation(line: 27, column: 44, scope: !21)
 // CHECK:STDOUT: !23 = !DILocation(line: 27, column: 37, scope: !21)
-// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "TestNeq", scope: null, file: !3, line: 30, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "TestNeq", linkageName: "TestNeq", scope: null, file: !3, line: 30, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !25 = !DILocation(line: 30, column: 45, scope: !24)
 // CHECK:STDOUT: !26 = !DILocation(line: 30, column: 38, scope: !24)
-// CHECK:STDOUT: !27 = distinct !DISubprogram(name: "TestLess", scope: null, file: !3, line: 33, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !27 = distinct !DISubprogram(name: "TestLess", linkageName: "TestLess", scope: null, file: !3, line: 33, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !28 = !DILocation(line: 33, column: 46, scope: !27)
 // CHECK:STDOUT: !29 = !DILocation(line: 33, column: 39, scope: !27)
-// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "TestLessEq", scope: null, file: !3, line: 36, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "TestLessEq", linkageName: "TestLessEq", scope: null, file: !3, line: 36, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !31 = !DILocation(line: 36, column: 48, scope: !30)
 // CHECK:STDOUT: !32 = !DILocation(line: 36, column: 41, scope: !30)
-// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "TestGreater", scope: null, file: !3, line: 39, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "TestGreater", linkageName: "TestGreater", scope: null, file: !3, line: 39, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !34 = !DILocation(line: 39, column: 49, scope: !33)
 // CHECK:STDOUT: !35 = !DILocation(line: 39, column: 42, scope: !33)
-// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "TestGreaterEq", scope: null, file: !3, line: 42, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "TestGreaterEq", linkageName: "TestGreaterEq", scope: null, file: !3, line: 42, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !37 = !DILocation(line: 42, column: 51, scope: !36)
 // CHECK:STDOUT: !38 = !DILocation(line: 42, column: 44, scope: !36)
diff --git a/toolchain/lower/testdata/builtins/int.carbon b/toolchain/lower/testdata/builtins/int.carbon
index bd81104f967a..39063db372f5 100644
--- a/toolchain/lower/testdata/builtins/int.carbon
+++ b/toolchain/lower/testdata/builtins/int.carbon
@@ -180,59 +180,59 @@ fn TestGreaterEq(a: i32, b: i32) -> bool { return GreaterEq(a, b); }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "int.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestNegate", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestNegate", linkageName: "TestNegate", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 39, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 12, column: 32, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAdd", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAdd", linkageName: "TestAdd", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 15, column: 44, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 37, scope: !9)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "TestSub", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "TestSub", linkageName: "TestSub", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 18, column: 44, scope: !12)
 // CHECK:STDOUT: !14 = !DILocation(line: 18, column: 37, scope: !12)
-// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "TestMul", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "TestMul", linkageName: "TestMul", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !16 = !DILocation(line: 21, column: 44, scope: !15)
 // CHECK:STDOUT: !17 = !DILocation(line: 21, column: 37, scope: !15)
-// CHECK:STDOUT: !18 = distinct !DISubprogram(name: "TestDiv", scope: null, file: !3, line: 24, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !18 = distinct !DISubprogram(name: "TestDiv", linkageName: "TestDiv", scope: null, file: !3, line: 24, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !19 = !DILocation(line: 24, column: 44, scope: !18)
 // CHECK:STDOUT: !20 = !DILocation(line: 24, column: 37, scope: !18)
-// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "TestMod", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "TestMod", linkageName: "TestMod", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !22 = !DILocation(line: 27, column: 44, scope: !21)
 // CHECK:STDOUT: !23 = !DILocation(line: 27, column: 37, scope: !21)
-// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "TestComplement", scope: null, file: !3, line: 30, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "TestComplement", linkageName: "TestComplement", scope: null, file: !3, line: 30, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !25 = !DILocation(line: 30, column: 43, scope: !24)
 // CHECK:STDOUT: !26 = !DILocation(line: 30, column: 36, scope: !24)
-// CHECK:STDOUT: !27 = distinct !DISubprogram(name: "TestAnd", scope: null, file: !3, line: 33, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !27 = distinct !DISubprogram(name: "TestAnd", linkageName: "TestAnd", scope: null, file: !3, line: 33, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !28 = !DILocation(line: 33, column: 44, scope: !27)
 // CHECK:STDOUT: !29 = !DILocation(line: 33, column: 37, scope: !27)
-// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "TestOr", scope: null, file: !3, line: 36, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "TestOr", linkageName: "TestOr", scope: null, file: !3, line: 36, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !31 = !DILocation(line: 36, column: 43, scope: !30)
 // CHECK:STDOUT: !32 = !DILocation(line: 36, column: 36, scope: !30)
-// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "TestXor", scope: null, file: !3, line: 39, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "TestXor", linkageName: "TestXor", scope: null, file: !3, line: 39, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !34 = !DILocation(line: 39, column: 44, scope: !33)
 // CHECK:STDOUT: !35 = !DILocation(line: 39, column: 37, scope: !33)
-// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "TestLeftShift", scope: null, file: !3, line: 42, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "TestLeftShift", linkageName: "TestLeftShift", scope: null, file: !3, line: 42, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !37 = !DILocation(line: 42, column: 50, scope: !36)
 // CHECK:STDOUT: !38 = !DILocation(line: 42, column: 43, scope: !36)
-// CHECK:STDOUT: !39 = distinct !DISubprogram(name: "TestRightShift", scope: null, file: !3, line: 45, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !39 = distinct !DISubprogram(name: "TestRightShift", linkageName: "TestRightShift", scope: null, file: !3, line: 45, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !40 = !DILocation(line: 45, column: 51, scope: !39)
 // CHECK:STDOUT: !41 = !DILocation(line: 45, column: 44, scope: !39)
-// CHECK:STDOUT: !42 = distinct !DISubprogram(name: "TestEq", scope: null, file: !3, line: 48, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !42 = distinct !DISubprogram(name: "TestEq", linkageName: "TestEq", scope: null, file: !3, line: 48, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !43 = !DILocation(line: 48, column: 44, scope: !42)
 // CHECK:STDOUT: !44 = !DILocation(line: 48, column: 37, scope: !42)
-// CHECK:STDOUT: !45 = distinct !DISubprogram(name: "TestNeq", scope: null, file: !3, line: 51, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !45 = distinct !DISubprogram(name: "TestNeq", linkageName: "TestNeq", scope: null, file: !3, line: 51, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !46 = !DILocation(line: 51, column: 45, scope: !45)
 // CHECK:STDOUT: !47 = !DILocation(line: 51, column: 38, scope: !45)
-// CHECK:STDOUT: !48 = distinct !DISubprogram(name: "TestLess", scope: null, file: !3, line: 54, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !48 = distinct !DISubprogram(name: "TestLess", linkageName: "TestLess", scope: null, file: !3, line: 54, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !49 = !DILocation(line: 54, column: 46, scope: !48)
 // CHECK:STDOUT: !50 = !DILocation(line: 54, column: 39, scope: !48)
-// CHECK:STDOUT: !51 = distinct !DISubprogram(name: "TestLessEq", scope: null, file: !3, line: 57, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !51 = distinct !DISubprogram(name: "TestLessEq", linkageName: "TestLessEq", scope: null, file: !3, line: 57, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !52 = !DILocation(line: 57, column: 48, scope: !51)
 // CHECK:STDOUT: !53 = !DILocation(line: 57, column: 41, scope: !51)
-// CHECK:STDOUT: !54 = distinct !DISubprogram(name: "TestGreater", scope: null, file: !3, line: 60, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !54 = distinct !DISubprogram(name: "TestGreater", linkageName: "TestGreater", scope: null, file: !3, line: 60, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !55 = !DILocation(line: 60, column: 49, scope: !54)
 // CHECK:STDOUT: !56 = !DILocation(line: 60, column: 42, scope: !54)
-// CHECK:STDOUT: !57 = distinct !DISubprogram(name: "TestGreaterEq", scope: null, file: !3, line: 63, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !57 = distinct !DISubprogram(name: "TestGreaterEq", linkageName: "TestGreaterEq", scope: null, file: !3, line: 63, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !58 = !DILocation(line: 63, column: 51, scope: !57)
 // CHECK:STDOUT: !59 = !DILocation(line: 63, column: 44, scope: !57)
diff --git a/toolchain/lower/testdata/builtins/method_vs_nonmethod.carbon b/toolchain/lower/testdata/builtins/method_vs_nonmethod.carbon
index 9841f8ec47d0..5cefc7af7d5d 100644
--- a/toolchain/lower/testdata/builtins/method_vs_nonmethod.carbon
+++ b/toolchain/lower/testdata/builtins/method_vs_nonmethod.carbon
@@ -36,11 +36,11 @@ fn TestAddMethod(a: i32, b: i32) -> i32 { return a.(AddMethod)(b); }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "method_vs_nonmethod.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestAddNonmethod", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestAddNonmethod", linkageName: "TestAddNonmethod", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 53, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 14, column: 46, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAddMethod", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAddMethod", linkageName: "TestAddMethod", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 15, column: 50, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 43, scope: !9)
diff --git a/toolchain/lower/testdata/builtins/overloaded_operator.carbon b/toolchain/lower/testdata/builtins/overloaded_operator.carbon
index 8d8db8d46e37..6aef3a0d517a 100644
--- a/toolchain/lower/testdata/builtins/overloaded_operator.carbon
+++ b/toolchain/lower/testdata/builtins/overloaded_operator.carbon
@@ -38,7 +38,7 @@ fn AddThreeIntegers(a: i32, b: i32, c: i32) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "overloaded_operator.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "AddThreeIntegers", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "AddThreeIntegers", linkageName: "AddThreeIntegers", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 18, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/builtins/print.carbon b/toolchain/lower/testdata/builtins/print.carbon
index bdbf50950f6d..577cef9d00a3 100644
--- a/toolchain/lower/testdata/builtins/print.carbon
+++ b/toolchain/lower/testdata/builtins/print.carbon
@@ -32,7 +32,7 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "print.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/builtins/types.carbon b/toolchain/lower/testdata/builtins/types.carbon
index 14da2c494ea9..dc84466143c3 100644
--- a/toolchain/lower/testdata/builtins/types.carbon
+++ b/toolchain/lower/testdata/builtins/types.carbon
@@ -39,7 +39,7 @@ fn F() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "types.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 16, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/builtins/uint.carbon b/toolchain/lower/testdata/builtins/uint.carbon
index 45d3e1c229ec..275f433bbafc 100644
--- a/toolchain/lower/testdata/builtins/uint.carbon
+++ b/toolchain/lower/testdata/builtins/uint.carbon
@@ -180,59 +180,59 @@ fn TestGreaterEq(a: u64, b: u64) -> bool { return GreaterEq(a, b); }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "uint.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestNegate", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "TestNegate", linkageName: "TestNegate", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 39, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 12, column: 32, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAdd", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "TestAdd", linkageName: "TestAdd", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 15, column: 44, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 37, scope: !9)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "TestSub", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "TestSub", linkageName: "TestSub", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 18, column: 44, scope: !12)
 // CHECK:STDOUT: !14 = !DILocation(line: 18, column: 37, scope: !12)
-// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "TestMul", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "TestMul", linkageName: "TestMul", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !16 = !DILocation(line: 21, column: 44, scope: !15)
 // CHECK:STDOUT: !17 = !DILocation(line: 21, column: 37, scope: !15)
-// CHECK:STDOUT: !18 = distinct !DISubprogram(name: "TestDiv", scope: null, file: !3, line: 24, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !18 = distinct !DISubprogram(name: "TestDiv", linkageName: "TestDiv", scope: null, file: !3, line: 24, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !19 = !DILocation(line: 24, column: 44, scope: !18)
 // CHECK:STDOUT: !20 = !DILocation(line: 24, column: 37, scope: !18)
-// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "TestMod", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "TestMod", linkageName: "TestMod", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !22 = !DILocation(line: 27, column: 44, scope: !21)
 // CHECK:STDOUT: !23 = !DILocation(line: 27, column: 37, scope: !21)
-// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "TestComplement", scope: null, file: !3, line: 30, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !24 = distinct !DISubprogram(name: "TestComplement", linkageName: "TestComplement", scope: null, file: !3, line: 30, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !25 = !DILocation(line: 30, column: 43, scope: !24)
 // CHECK:STDOUT: !26 = !DILocation(line: 30, column: 36, scope: !24)
-// CHECK:STDOUT: !27 = distinct !DISubprogram(name: "TestAnd", scope: null, file: !3, line: 33, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !27 = distinct !DISubprogram(name: "TestAnd", linkageName: "TestAnd", scope: null, file: !3, line: 33, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !28 = !DILocation(line: 33, column: 44, scope: !27)
 // CHECK:STDOUT: !29 = !DILocation(line: 33, column: 37, scope: !27)
-// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "TestOr", scope: null, file: !3, line: 36, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "TestOr", linkageName: "TestOr", scope: null, file: !3, line: 36, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !31 = !DILocation(line: 36, column: 43, scope: !30)
 // CHECK:STDOUT: !32 = !DILocation(line: 36, column: 36, scope: !30)
-// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "TestXor", scope: null, file: !3, line: 39, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !33 = distinct !DISubprogram(name: "TestXor", linkageName: "TestXor", scope: null, file: !3, line: 39, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !34 = !DILocation(line: 39, column: 44, scope: !33)
 // CHECK:STDOUT: !35 = !DILocation(line: 39, column: 37, scope: !33)
-// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "TestLeftShift", scope: null, file: !3, line: 42, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "TestLeftShift", linkageName: "TestLeftShift", scope: null, file: !3, line: 42, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !37 = !DILocation(line: 42, column: 50, scope: !36)
 // CHECK:STDOUT: !38 = !DILocation(line: 42, column: 43, scope: !36)
-// CHECK:STDOUT: !39 = distinct !DISubprogram(name: "TestRightShift", scope: null, file: !3, line: 45, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !39 = distinct !DISubprogram(name: "TestRightShift", linkageName: "TestRightShift", scope: null, file: !3, line: 45, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !40 = !DILocation(line: 45, column: 51, scope: !39)
 // CHECK:STDOUT: !41 = !DILocation(line: 45, column: 44, scope: !39)
-// CHECK:STDOUT: !42 = distinct !DISubprogram(name: "TestEq", scope: null, file: !3, line: 48, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !42 = distinct !DISubprogram(name: "TestEq", linkageName: "TestEq", scope: null, file: !3, line: 48, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !43 = !DILocation(line: 48, column: 44, scope: !42)
 // CHECK:STDOUT: !44 = !DILocation(line: 48, column: 37, scope: !42)
-// CHECK:STDOUT: !45 = distinct !DISubprogram(name: "TestNeq", scope: null, file: !3, line: 51, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !45 = distinct !DISubprogram(name: "TestNeq", linkageName: "TestNeq", scope: null, file: !3, line: 51, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !46 = !DILocation(line: 51, column: 45, scope: !45)
 // CHECK:STDOUT: !47 = !DILocation(line: 51, column: 38, scope: !45)
-// CHECK:STDOUT: !48 = distinct !DISubprogram(name: "TestLess", scope: null, file: !3, line: 54, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !48 = distinct !DISubprogram(name: "TestLess", linkageName: "TestLess", scope: null, file: !3, line: 54, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !49 = !DILocation(line: 54, column: 46, scope: !48)
 // CHECK:STDOUT: !50 = !DILocation(line: 54, column: 39, scope: !48)
-// CHECK:STDOUT: !51 = distinct !DISubprogram(name: "TestLessEq", scope: null, file: !3, line: 57, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !51 = distinct !DISubprogram(name: "TestLessEq", linkageName: "TestLessEq", scope: null, file: !3, line: 57, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !52 = !DILocation(line: 57, column: 48, scope: !51)
 // CHECK:STDOUT: !53 = !DILocation(line: 57, column: 41, scope: !51)
-// CHECK:STDOUT: !54 = distinct !DISubprogram(name: "TestGreater", scope: null, file: !3, line: 60, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !54 = distinct !DISubprogram(name: "TestGreater", linkageName: "TestGreater", scope: null, file: !3, line: 60, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !55 = !DILocation(line: 60, column: 49, scope: !54)
 // CHECK:STDOUT: !56 = !DILocation(line: 60, column: 42, scope: !54)
-// CHECK:STDOUT: !57 = distinct !DISubprogram(name: "TestGreaterEq", scope: null, file: !3, line: 63, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !57 = distinct !DISubprogram(name: "TestGreaterEq", linkageName: "TestGreaterEq", scope: null, file: !3, line: 63, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !58 = !DILocation(line: 63, column: 51, scope: !57)
 // CHECK:STDOUT: !59 = !DILocation(line: 63, column: 44, scope: !57)
diff --git a/toolchain/lower/testdata/class/adapt.carbon b/toolchain/lower/testdata/class/adapt.carbon
index 6970d9533224..26e74311b3be 100644
--- a/toolchain/lower/testdata/class/adapt.carbon
+++ b/toolchain/lower/testdata/class/adapt.carbon
@@ -97,18 +97,18 @@ fn DoStuff(a: Int) -> Int {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "adapt_class.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Make", scope: null, file: !3, line: 8, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Make", linkageName: "Make", scope: null, file: !3, line: 8, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 9, column: 12, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 9, column: 5, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Make.1", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Make", linkageName: "Make.1", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 17, column: 12, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 17, column: 5, scope: !9)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "GetB", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "GetB", linkageName: "GetB", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 22, column: 12, scope: !12)
 // CHECK:STDOUT: !14 = !DILocation(line: 22, column: 5, scope: !12)
-// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "Use", scope: null, file: !3, line: 26, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "Use", linkageName: "Use", scope: null, file: !3, line: 26, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !16 = !DILocation(line: 27, column: 7, scope: !15)
 // CHECK:STDOUT: !17 = !DILocation(line: 27, column: 25, scope: !15)
 // CHECK:STDOUT: !18 = !DILocation(line: 28, column: 10, scope: !15)
@@ -128,7 +128,7 @@ fn DoStuff(a: Int) -> Int {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "adapt_int.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "DoStuff", scope: null, file: !3, line: 8, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "DoStuff", linkageName: "DoStuff", scope: null, file: !3, line: 8, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 9, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/class/base.carbon b/toolchain/lower/testdata/class/base.carbon
index a4fa4f90e470..a5f7d4d38d91 100644
--- a/toolchain/lower/testdata/class/base.carbon
+++ b/toolchain/lower/testdata/class/base.carbon
@@ -76,16 +76,16 @@ fn Convert(p: Derived*) -> Base* {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "base.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Make", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Make", linkageName: "Make", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 22, column: 10, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 22, column: 19, scope: !4)
 // CHECK:STDOUT: !9 = !DILocation(line: 22, column: 3, scope: !4)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Access", scope: null, file: !3, line: 25, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Access", linkageName: "Access", scope: null, file: !3, line: 25, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 26, column: 11, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 26, column: 16, scope: !10)
 // CHECK:STDOUT: !13 = !DILocation(line: 26, column: 10, scope: !10)
 // CHECK:STDOUT: !14 = !DILocation(line: 26, column: 3, scope: !10)
-// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "Convert", scope: null, file: !3, line: 29, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !15 = distinct !DISubprogram(name: "Convert", linkageName: "Convert", scope: null, file: !3, line: 29, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !16 = !DILocation(line: 30, column: 3, scope: !15)
diff --git a/toolchain/lower/testdata/class/basic.carbon b/toolchain/lower/testdata/class/basic.carbon
index 2e238f0f4c8a..f3e3b0f6b0a5 100644
--- a/toolchain/lower/testdata/class/basic.carbon
+++ b/toolchain/lower/testdata/class/basic.carbon
@@ -40,7 +40,7 @@ fn Run() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "basic.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 19, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/class/field.carbon b/toolchain/lower/testdata/class/field.carbon
index 634a758ec2a5..670cdfc593ad 100644
--- a/toolchain/lower/testdata/class/field.carbon
+++ b/toolchain/lower/testdata/class/field.carbon
@@ -54,13 +54,13 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "field.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 17, column: 12, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 17, column: 10, scope: !4)
 // CHECK:STDOUT: !9 = !DILocation(line: 17, column: 3, scope: !4)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 21, column: 7, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 22, column: 3, scope: !10)
 // CHECK:STDOUT: !13 = !DILocation(line: 23, column: 3, scope: !10)
diff --git a/toolchain/lower/testdata/class/method.carbon b/toolchain/lower/testdata/class/method.carbon
index a2bd6ab20468..2769ab0f2c6f 100644
--- a/toolchain/lower/testdata/class/method.carbon
+++ b/toolchain/lower/testdata/class/method.carbon
@@ -41,7 +41,7 @@ fn F(p: C*) {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "method.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 19, column: 16, scope: !4)
diff --git a/toolchain/lower/testdata/class/self.carbon b/toolchain/lower/testdata/class/self.carbon
index 0486e626769f..55636f479d5e 100644
--- a/toolchain/lower/testdata/class/self.carbon
+++ b/toolchain/lower/testdata/class/self.carbon
@@ -47,11 +47,11 @@ fn C.Set[addr self: C*]() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "self.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Get", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Get", linkageName: "Get", scope: null, file: !3, line: 18, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 19, column: 10, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 19, column: 3, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Set", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Set", linkageName: "Set", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 23, column: 3, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 22, column: 1, scope: !9)
diff --git a/toolchain/lower/testdata/class/value_access.carbon b/toolchain/lower/testdata/class/value_access.carbon
index 6eb30ecc9ff3..8604499c6304 100644
--- a/toolchain/lower/testdata/class/value_access.carbon
+++ b/toolchain/lower/testdata/class/value_access.carbon
@@ -50,7 +50,7 @@ fn F(c: C) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "value_access.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 19, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/function/call/empty_struct.carbon b/toolchain/lower/testdata/function/call/empty_struct.carbon
index 57f9505b3b88..56d9da938111 100644
--- a/toolchain/lower/testdata/function/call/empty_struct.carbon
+++ b/toolchain/lower/testdata/function/call/empty_struct.carbon
@@ -38,11 +38,11 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "empty_struct.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", linkageName: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 16, column: 7, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 16, column: 15, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/empty_tuple.carbon b/toolchain/lower/testdata/function/call/empty_tuple.carbon
index d2c71c3fe067..f79c32e899d7 100644
--- a/toolchain/lower/testdata/function/call/empty_tuple.carbon
+++ b/toolchain/lower/testdata/function/call/empty_tuple.carbon
@@ -38,11 +38,11 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "empty_tuple.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", linkageName: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 16, column: 7, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 16, column: 15, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/i32.carbon b/toolchain/lower/testdata/function/call/i32.carbon
index 4ebde45a8864..3c15547d13de 100644
--- a/toolchain/lower/testdata/function/call/i32.carbon
+++ b/toolchain/lower/testdata/function/call/i32.carbon
@@ -39,11 +39,11 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "i32.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", linkageName: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 16, column: 7, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 16, column: 16, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 16, column: 3, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon b/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon
index d145e03edd0a..f1ca435bf05f 100644
--- a/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon
+++ b/toolchain/lower/testdata/function/call/implicit_empty_tuple_as_arg.carbon
@@ -46,13 +46,13 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "implicit_empty_tuple_as_arg.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Bar", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Bar", linkageName: "Bar", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 23, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 17, column: 7, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 17, column: 19, scope: !10)
 // CHECK:STDOUT: !13 = !DILocation(line: 17, column: 15, scope: !10)
diff --git a/toolchain/lower/testdata/function/call/params_one.carbon b/toolchain/lower/testdata/function/call/params_one.carbon
index e5d2541c3d12..5ab33ecca831 100644
--- a/toolchain/lower/testdata/function/call/params_one.carbon
+++ b/toolchain/lower/testdata/function/call/params_one.carbon
@@ -35,10 +35,10 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_one.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 13, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/params_one_comma.carbon b/toolchain/lower/testdata/function/call/params_one_comma.carbon
index a4a752326b12..7855e9fa03ff 100644
--- a/toolchain/lower/testdata/function/call/params_one_comma.carbon
+++ b/toolchain/lower/testdata/function/call/params_one_comma.carbon
@@ -37,11 +37,11 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_one_comma.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 15, column: 3, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 13, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/params_two.carbon b/toolchain/lower/testdata/function/call/params_two.carbon
index deaef47197f7..fa1f2275a7b0 100644
--- a/toolchain/lower/testdata/function/call/params_two.carbon
+++ b/toolchain/lower/testdata/function/call/params_two.carbon
@@ -35,10 +35,10 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_two.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 13, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/params_two_comma.carbon b/toolchain/lower/testdata/function/call/params_two_comma.carbon
index 844b9054d8a7..871eee2ca5a6 100644
--- a/toolchain/lower/testdata/function/call/params_two_comma.carbon
+++ b/toolchain/lower/testdata/function/call/params_two_comma.carbon
@@ -37,11 +37,11 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_two_comma.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 15, column: 3, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 13, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/params_zero.carbon b/toolchain/lower/testdata/function/call/params_zero.carbon
index 1b585b57f3b9..42114b82b829 100644
--- a/toolchain/lower/testdata/function/call/params_zero.carbon
+++ b/toolchain/lower/testdata/function/call/params_zero.carbon
@@ -35,10 +35,10 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_zero.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 13, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/return_implicit.carbon b/toolchain/lower/testdata/function/call/return_implicit.carbon
index bd0243fc9f04..7f9669e4731c 100644
--- a/toolchain/lower/testdata/function/call/return_implicit.carbon
+++ b/toolchain/lower/testdata/function/call/return_implicit.carbon
@@ -38,11 +38,11 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "return_implicit.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "MakeImplicitEmptyTuple", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "MakeImplicitEmptyTuple", linkageName: "MakeImplicitEmptyTuple", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 16, column: 7, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 16, column: 15, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/struct_param.carbon b/toolchain/lower/testdata/function/call/struct_param.carbon
index b53aaf2766b9..2cf59d120afb 100644
--- a/toolchain/lower/testdata/function/call/struct_param.carbon
+++ b/toolchain/lower/testdata/function/call/struct_param.carbon
@@ -37,10 +37,10 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "struct_param.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 13, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/tuple_param.carbon b/toolchain/lower/testdata/function/call/tuple_param.carbon
index 191fa66a8624..1b33d29ece49 100644
--- a/toolchain/lower/testdata/function/call/tuple_param.carbon
+++ b/toolchain/lower/testdata/function/call/tuple_param.carbon
@@ -37,10 +37,10 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "tuple_param.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 13, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon b/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon
index 082e7edad913..02d943490641 100644
--- a/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon
+++ b/toolchain/lower/testdata/function/call/tuple_param_with_return_slot.carbon
@@ -54,7 +54,7 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "tuple_param_with_return_slot.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 11, scope: !4)
@@ -62,6 +62,6 @@ fn Main() {
 // CHECK:STDOUT: !9 = !DILocation(line: 12, column: 21, scope: !4)
 // CHECK:STDOUT: !10 = !DILocation(line: 12, column: 10, scope: !4)
 // CHECK:STDOUT: !11 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 16, column: 3, scope: !12)
 // CHECK:STDOUT: !14 = !DILocation(line: 15, column: 1, scope: !12)
diff --git a/toolchain/lower/testdata/function/call/var_param.carbon b/toolchain/lower/testdata/function/call/var_param.carbon
index b26ece86b3bc..1e2b97ba4668 100644
--- a/toolchain/lower/testdata/function/call/var_param.carbon
+++ b/toolchain/lower/testdata/function/call/var_param.carbon
@@ -39,11 +39,11 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "var_param.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "DoNothing", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "DoNothing", linkageName: "DoNothing", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 7, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 14, column: 3, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 13, scope: !8)
diff --git a/toolchain/lower/testdata/function/declaration/simple.carbon b/toolchain/lower/testdata/function/declaration/simple.carbon
index 25a55f74660c..21a4aa4745f9 100644
--- a/toolchain/lower/testdata/function/declaration/simple.carbon
+++ b/toolchain/lower/testdata/function/declaration/simple.carbon
@@ -30,7 +30,7 @@ fn G(n: i32) { F(n); }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "simple.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 13, column: 16, scope: !4)
diff --git a/toolchain/lower/testdata/function/definition/empty_struct.carbon b/toolchain/lower/testdata/function/definition/empty_struct.carbon
index d2422d2c26ef..19fab4912ff2 100644
--- a/toolchain/lower/testdata/function/definition/empty_struct.carbon
+++ b/toolchain/lower/testdata/function/definition/empty_struct.carbon
@@ -26,7 +26,7 @@ fn Echo(a: {}) {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "empty_struct.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Echo", linkageName: "Echo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/function/definition/params_one.carbon b/toolchain/lower/testdata/function/definition/params_one.carbon
index d5c1b67cb47e..0ffe22f00391 100644
--- a/toolchain/lower/testdata/function/definition/params_one.carbon
+++ b/toolchain/lower/testdata/function/definition/params_one.carbon
@@ -25,7 +25,7 @@ fn Foo(a: i32) {}
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_one.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/function/definition/params_two.carbon b/toolchain/lower/testdata/function/definition/params_two.carbon
index 1f76d9e94a1b..23322afc2473 100644
--- a/toolchain/lower/testdata/function/definition/params_two.carbon
+++ b/toolchain/lower/testdata/function/definition/params_two.carbon
@@ -25,7 +25,7 @@ fn Foo(a: i32, b: i32) {}
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_two.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/function/definition/params_zero.carbon b/toolchain/lower/testdata/function/definition/params_zero.carbon
index 4aa0a3fea095..0bc600ff6269 100644
--- a/toolchain/lower/testdata/function/definition/params_zero.carbon
+++ b/toolchain/lower/testdata/function/definition/params_zero.carbon
@@ -25,7 +25,7 @@ fn Foo() {}
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "params_zero.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Foo", linkageName: "Foo", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/function/definition/raw_name.carbon b/toolchain/lower/testdata/function/definition/raw_name.carbon
index d8c38468fad9..7737ab7493ce 100644
--- a/toolchain/lower/testdata/function/definition/raw_name.carbon
+++ b/toolchain/lower/testdata/function/definition/raw_name.carbon
@@ -26,7 +26,7 @@ fn r#self() {}
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "raw_name.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "self", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "self", linkageName: "self", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/global/class_obj.carbon b/toolchain/lower/testdata/global/class_obj.carbon
index c7a6dfd80661..408adfaaa6e0 100644
--- a/toolchain/lower/testdata/global/class_obj.carbon
+++ b/toolchain/lower/testdata/global/class_obj.carbon
@@ -36,7 +36,7 @@ var a: A = {};
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "class_obj.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "__global_init", linkageName: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/global/class_with_fun.carbon b/toolchain/lower/testdata/global/class_with_fun.carbon
index fe99388c5d26..e1b5fedf5643 100644
--- a/toolchain/lower/testdata/global/class_with_fun.carbon
+++ b/toolchain/lower/testdata/global/class_with_fun.carbon
@@ -50,10 +50,10 @@ var a: A = {};
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "class_with_fun.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "ret_a", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "ret_a", linkageName: "ret_a", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 13, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "__global_init", linkageName: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 16, column: 1, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 4294967295, scope: !8)
diff --git a/toolchain/lower/testdata/global/simple_init.carbon b/toolchain/lower/testdata/global/simple_init.carbon
index 47bf76ae3bba..e8fb6939d272 100644
--- a/toolchain/lower/testdata/global/simple_init.carbon
+++ b/toolchain/lower/testdata/global/simple_init.carbon
@@ -31,7 +31,7 @@ var a: i32 = 0;
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "simple_init.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "__global_init", linkageName: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 10, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/global/simple_with_fun.carbon b/toolchain/lower/testdata/global/simple_with_fun.carbon
index ad14902f2dc2..7534d359d774 100644
--- a/toolchain/lower/testdata/global/simple_with_fun.carbon
+++ b/toolchain/lower/testdata/global/simple_with_fun.carbon
@@ -42,11 +42,11 @@ var a: i32 = test_a();
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "simple_with_fun.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "test_a", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "test_a", linkageName: "test_a", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "__global_init", linkageName: "__global_init", scope: null, file: !3, line: 4294967295, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 15, column: 14, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 15, column: 1, scope: !8)
 // CHECK:STDOUT: !11 = !DILocation(line: 4294967295, scope: !8)
diff --git a/toolchain/lower/testdata/if/else.carbon b/toolchain/lower/testdata/if/else.carbon
index d1d30f81f970..567f88fbebd4 100644
--- a/toolchain/lower/testdata/if/else.carbon
+++ b/toolchain/lower/testdata/if/else.carbon
@@ -63,15 +63,15 @@ fn If(b: bool) {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "else.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 12, column: 1, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "H", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "H", linkageName: "H", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 13, column: 1, scope: !10)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "If", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "If", linkageName: "If", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 16, column: 6, scope: !12)
 // CHECK:STDOUT: !14 = !DILocation(line: 17, column: 5, scope: !12)
 // CHECK:STDOUT: !15 = !DILocation(line: 16, column: 3, scope: !12)
diff --git a/toolchain/lower/testdata/if/no_else.carbon b/toolchain/lower/testdata/if/no_else.carbon
index 43d5c7aabaee..a95c0e1e6e4c 100644
--- a/toolchain/lower/testdata/if/no_else.carbon
+++ b/toolchain/lower/testdata/if/no_else.carbon
@@ -51,13 +51,13 @@ fn If(b: bool) {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "no_else.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 12, column: 1, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "If", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "If", linkageName: "If", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 6, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 16, column: 5, scope: !10)
 // CHECK:STDOUT: !13 = !DILocation(line: 15, column: 3, scope: !10)
diff --git a/toolchain/lower/testdata/if_expr/basic.carbon b/toolchain/lower/testdata/if_expr/basic.carbon
index 92bc097a5c47..e2f814687cc5 100644
--- a/toolchain/lower/testdata/if_expr/basic.carbon
+++ b/toolchain/lower/testdata/if_expr/basic.carbon
@@ -52,13 +52,13 @@ fn Select(b: bool) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "basic.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 17, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 12, column: 17, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Select", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Select", linkageName: "Select", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 10, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 15, column: 20, scope: !10)
 // CHECK:STDOUT: !13 = !DILocation(line: 15, column: 29, scope: !10)
diff --git a/toolchain/lower/testdata/if_expr/empty_block.carbon b/toolchain/lower/testdata/if_expr/empty_block.carbon
index d01138f7c14e..fda57da20c9d 100644
--- a/toolchain/lower/testdata/if_expr/empty_block.carbon
+++ b/toolchain/lower/testdata/if_expr/empty_block.carbon
@@ -57,7 +57,7 @@ fn Select(b: bool, c: bool, d: bool) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "empty_block.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Select", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Select", linkageName: "Select", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/impl/assoc_fn_alias.carbon b/toolchain/lower/testdata/impl/assoc_fn_alias.carbon
index 0329104f7138..46eb2091ba3e 100644
--- a/toolchain/lower/testdata/impl/assoc_fn_alias.carbon
+++ b/toolchain/lower/testdata/impl/assoc_fn_alias.carbon
@@ -50,11 +50,11 @@ fn Call(a: A) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "assoc_fn_alias.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 22, column: 12, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 22, column: 5, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Call", scope: null, file: !3, line: 26, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Call", linkageName: "Call", scope: null, file: !3, line: 26, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 27, column: 10, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 27, column: 3, scope: !9)
diff --git a/toolchain/lower/testdata/impl/extend_impl.carbon b/toolchain/lower/testdata/impl/extend_impl.carbon
index e7f453a33714..9e2b3799470f 100644
--- a/toolchain/lower/testdata/impl/extend_impl.carbon
+++ b/toolchain/lower/testdata/impl/extend_impl.carbon
@@ -55,13 +55,13 @@ fn InstanceAccess(a: A) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "extend_impl.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 18, column: 7, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "TypeAccess", scope: null, file: !3, line: 23, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "TypeAccess", linkageName: "TypeAccess", scope: null, file: !3, line: 23, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 24, column: 10, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 24, column: 3, scope: !8)
-// CHECK:STDOUT: !11 = distinct !DISubprogram(name: "InstanceAccess", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !11 = distinct !DISubprogram(name: "InstanceAccess", linkageName: "InstanceAccess", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !12 = !DILocation(line: 28, column: 10, scope: !11)
 // CHECK:STDOUT: !13 = !DILocation(line: 28, column: 3, scope: !11)
diff --git a/toolchain/lower/testdata/impl/impl.carbon b/toolchain/lower/testdata/impl/impl.carbon
index c23571083a0e..060c07a290c2 100644
--- a/toolchain/lower/testdata/impl/impl.carbon
+++ b/toolchain/lower/testdata/impl/impl.carbon
@@ -49,11 +49,11 @@ fn Call(a: A) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "impl.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 21, column: 12, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 21, column: 5, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Call", scope: null, file: !3, line: 25, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Call", linkageName: "Call", scope: null, file: !3, line: 25, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 26, column: 10, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 26, column: 3, scope: !9)
diff --git a/toolchain/lower/testdata/impl/instance_method.carbon b/toolchain/lower/testdata/impl/instance_method.carbon
index bbcc5b6a7c29..c6c20f0fe98d 100644
--- a/toolchain/lower/testdata/impl/instance_method.carbon
+++ b/toolchain/lower/testdata/impl/instance_method.carbon
@@ -47,10 +47,10 @@ fn Call(a: A*) -> A* {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "instance_method.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Get", scope: null, file: !3, line: 19, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Get", linkageName: "Get", scope: null, file: !3, line: 19, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 20, column: 7, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Call", scope: null, file: !3, line: 25, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Call", linkageName: "Call", scope: null, file: !3, line: 25, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 26, column: 10, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 26, column: 3, scope: !8)
diff --git a/toolchain/lower/testdata/index/array_element_access.carbon b/toolchain/lower/testdata/index/array_element_access.carbon
index 5b17d63bc05d..20ee6928f201 100644
--- a/toolchain/lower/testdata/index/array_element_access.carbon
+++ b/toolchain/lower/testdata/index/array_element_access.carbon
@@ -84,15 +84,15 @@ fn Run() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "array_element_access.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "A", scope: null, file: !3, line: 10, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "A", linkageName: "A", scope: null, file: !3, line: 10, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 10, column: 31, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 10, column: 24, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "B", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "B", linkageName: "B", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 12, column: 29, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 12, column: 22, scope: !9)
-// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !13 = !DILocation(line: 15, column: 7, scope: !12)
 // CHECK:STDOUT: !14 = !DILocation(line: 15, column: 21, scope: !12)
 // CHECK:STDOUT: !15 = !DILocation(line: 16, column: 7, scope: !12)
diff --git a/toolchain/lower/testdata/interface/assoc.carbon b/toolchain/lower/testdata/interface/assoc.carbon
index f06c7323889c..5c4881024cea 100644
--- a/toolchain/lower/testdata/interface/assoc.carbon
+++ b/toolchain/lower/testdata/interface/assoc.carbon
@@ -29,7 +29,7 @@ fn F() { I.Assoc; }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "assoc.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 15, column: 1, scope: !4)
diff --git a/toolchain/lower/testdata/interface/basic.carbon b/toolchain/lower/testdata/interface/basic.carbon
index de91482f7b02..1f9062e2b531 100644
--- a/toolchain/lower/testdata/interface/basic.carbon
+++ b/toolchain/lower/testdata/interface/basic.carbon
@@ -41,9 +41,9 @@ fn G(T: J) {}
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "basic.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 17, column: 19, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 22, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 22, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/let/local.carbon b/toolchain/lower/testdata/let/local.carbon
index 95873f3df29f..03ba276789a2 100644
--- a/toolchain/lower/testdata/let/local.carbon
+++ b/toolchain/lower/testdata/let/local.carbon
@@ -29,7 +29,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "local.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/let/tuple.carbon b/toolchain/lower/testdata/let/tuple.carbon
index 67e10118db06..3cb4f9b23b79 100644
--- a/toolchain/lower/testdata/let/tuple.carbon
+++ b/toolchain/lower/testdata/let/tuple.carbon
@@ -81,7 +81,7 @@ fn F() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "tuple.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/namespace/function.carbon b/toolchain/lower/testdata/namespace/function.carbon
index 1aa9cd5c09cd..f8121b0702e4 100644
--- a/toolchain/lower/testdata/namespace/function.carbon
+++ b/toolchain/lower/testdata/namespace/function.carbon
@@ -47,12 +47,12 @@ fn Bar() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "function.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Baz", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Baz", linkageName: "Baz", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Baz.1", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Baz", linkageName: "Baz.1", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 17, column: 1, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Bar", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Bar", linkageName: "Bar", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 21, column: 3, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 20, column: 1, scope: !10)
diff --git a/toolchain/lower/testdata/namespace/nested.carbon b/toolchain/lower/testdata/namespace/nested.carbon
index edb92a291046..5da934315b16 100644
--- a/toolchain/lower/testdata/namespace/nested.carbon
+++ b/toolchain/lower/testdata/namespace/nested.carbon
@@ -39,10 +39,10 @@ fn Foo.Bar.Baz() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "nested.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Wiz", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Wiz", linkageName: "Wiz", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Baz", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Baz", linkageName: "Baz", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 18, column: 3, scope: !8)
 // CHECK:STDOUT: !10 = !DILocation(line: 17, column: 1, scope: !8)
diff --git a/toolchain/lower/testdata/operators/and.carbon b/toolchain/lower/testdata/operators/and.carbon
index f12c7d552153..9737e3ef7041 100644
--- a/toolchain/lower/testdata/operators/and.carbon
+++ b/toolchain/lower/testdata/operators/and.carbon
@@ -49,13 +49,13 @@ fn And() -> bool {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "and.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 18, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 12, column: 18, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "And", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "And", linkageName: "And", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 10, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 15, column: 18, scope: !10)
 // CHECK:STDOUT: !13 = !DILocation(line: 15, column: 3, scope: !10)
diff --git a/toolchain/lower/testdata/operators/and_empty_block.carbon b/toolchain/lower/testdata/operators/and_empty_block.carbon
index 625b8701b4ff..4b71ab9fd872 100644
--- a/toolchain/lower/testdata/operators/and_empty_block.carbon
+++ b/toolchain/lower/testdata/operators/and_empty_block.carbon
@@ -36,7 +36,7 @@ fn And(b: bool, c: bool) -> bool {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "and_empty_block.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "And", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "And", linkageName: "And", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/operators/assignment.carbon b/toolchain/lower/testdata/operators/assignment.carbon
index 9948bec18008..29a5e9afe9e2 100644
--- a/toolchain/lower/testdata/operators/assignment.carbon
+++ b/toolchain/lower/testdata/operators/assignment.carbon
@@ -44,7 +44,7 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "assignment.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/operators/not.carbon b/toolchain/lower/testdata/operators/not.carbon
index daa87aabd57f..b9d494fd38d4 100644
--- a/toolchain/lower/testdata/operators/not.carbon
+++ b/toolchain/lower/testdata/operators/not.carbon
@@ -28,7 +28,7 @@ fn Not(b: bool) -> bool {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "not.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Not", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Not", linkageName: "Not", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/operators/or.carbon b/toolchain/lower/testdata/operators/or.carbon
index 3155e4d16e09..cb4c7bd8674e 100644
--- a/toolchain/lower/testdata/operators/or.carbon
+++ b/toolchain/lower/testdata/operators/or.carbon
@@ -50,13 +50,13 @@ fn Or() -> bool {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "or.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 18, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 12, column: 18, scope: !8)
-// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Or", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "Or", linkageName: "Or", scope: null, file: !3, line: 14, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !11 = !DILocation(line: 15, column: 10, scope: !10)
 // CHECK:STDOUT: !12 = !DILocation(line: 15, column: 17, scope: !10)
 // CHECK:STDOUT: !13 = !DILocation(line: 15, column: 3, scope: !10)
diff --git a/toolchain/lower/testdata/operators/or_empty_block.carbon b/toolchain/lower/testdata/operators/or_empty_block.carbon
index f795aba6e795..f56020b91c65 100644
--- a/toolchain/lower/testdata/operators/or_empty_block.carbon
+++ b/toolchain/lower/testdata/operators/or_empty_block.carbon
@@ -37,7 +37,7 @@ fn Or(b: bool, c: bool) -> bool {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "or_empty_block.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Or", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Or", linkageName: "Or", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/operators/overloaded.carbon b/toolchain/lower/testdata/operators/overloaded.carbon
index bd19cb71bae0..daf3c39bca25 100644
--- a/toolchain/lower/testdata/operators/overloaded.carbon
+++ b/toolchain/lower/testdata/operators/overloaded.carbon
@@ -98,14 +98,14 @@ fn Calculate(a: Number, b: Number) -> Number {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "overloaded.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Op", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Op", linkageName: "Op", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 17, column: 32, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 17, column: 28, scope: !4)
 // CHECK:STDOUT: !9 = !DILocation(line: 17, column: 12, scope: !4)
 // CHECK:STDOUT: !10 = !DILocation(line: 17, column: 5, scope: !4)
-// CHECK:STDOUT: !11 = distinct !DISubprogram(name: "Op.1", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !11 = distinct !DISubprogram(name: "Op", linkageName: "Op.1", scope: null, file: !3, line: 21, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !12 = !DILocation(line: 22, column: 29, scope: !11)
 // CHECK:STDOUT: !13 = !DILocation(line: 22, column: 50, scope: !11)
 // CHECK:STDOUT: !14 = !DILocation(line: 22, column: 28, scope: !11)
@@ -115,6 +115,6 @@ fn Calculate(a: Number, b: Number) -> Number {
 // CHECK:STDOUT: !18 = !DILocation(line: 23, column: 55, scope: !11)
 // CHECK:STDOUT: !19 = !DILocation(line: 22, column: 12, scope: !11)
 // CHECK:STDOUT: !20 = !DILocation(line: 22, column: 5, scope: !11)
-// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "Calculate", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !21 = distinct !DISubprogram(name: "Calculate", linkageName: "Calculate", scope: null, file: !3, line: 27, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !22 = !DILocation(line: 28, column: 10, scope: !21)
 // CHECK:STDOUT: !23 = !DILocation(line: 28, column: 3, scope: !21)
diff --git a/toolchain/lower/testdata/packages/cross_package_call.carbon b/toolchain/lower/testdata/packages/cross_package_call.carbon
index 6defae99e968..26141efa34f4 100644
--- a/toolchain/lower/testdata/packages/cross_package_call.carbon
+++ b/toolchain/lower/testdata/packages/cross_package_call.carbon
@@ -35,7 +35,7 @@ fn G() { A.F(); }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "a.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 4, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 4, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 4, column: 1, scope: !4)
@@ -57,7 +57,7 @@ fn G() { A.F(); }
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "b.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 4, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 4, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 4, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/pointer/address_of_field.carbon b/toolchain/lower/testdata/pointer/address_of_field.carbon
index 457453dbddb2..df3c583a3805 100644
--- a/toolchain/lower/testdata/pointer/address_of_field.carbon
+++ b/toolchain/lower/testdata/pointer/address_of_field.carbon
@@ -45,7 +45,7 @@ fn F() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "address_of_field.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/pointer/address_of_unused.carbon b/toolchain/lower/testdata/pointer/address_of_unused.carbon
index 78339742758d..a1e32f5ec158 100644
--- a/toolchain/lower/testdata/pointer/address_of_unused.carbon
+++ b/toolchain/lower/testdata/pointer/address_of_unused.carbon
@@ -30,7 +30,7 @@ fn F() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "address_of_unused.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/pointer/basic.carbon b/toolchain/lower/testdata/pointer/basic.carbon
index ecaee0e24238..78dc095d67bf 100644
--- a/toolchain/lower/testdata/pointer/basic.carbon
+++ b/toolchain/lower/testdata/pointer/basic.carbon
@@ -41,12 +41,12 @@ fn F() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "basic.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 10, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 12, column: 3, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 16, column: 7, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 16, column: 3, scope: !9)
 // CHECK:STDOUT: !12 = !DILocation(line: 17, column: 10, scope: !9)
diff --git a/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon b/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
index 1528ccd81f55..142ae5745cde 100644
--- a/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
+++ b/toolchain/lower/testdata/pointer/pointer_to_pointer.carbon
@@ -40,7 +40,7 @@ fn F(p: i32**) -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "pointer_to_pointer.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/return/code_after_return.carbon b/toolchain/lower/testdata/return/code_after_return.carbon
index 5e6e3011932e..40a3ce18b2a7 100644
--- a/toolchain/lower/testdata/return/code_after_return.carbon
+++ b/toolchain/lower/testdata/return/code_after_return.carbon
@@ -35,9 +35,9 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "code_after_return.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 1, scope: !4)
-// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !8 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !9 = !DILocation(line: 14, column: 3, scope: !8)
diff --git a/toolchain/lower/testdata/return/no_value.carbon b/toolchain/lower/testdata/return/no_value.carbon
index dc5956fcb3d2..a4e43cf18441 100644
--- a/toolchain/lower/testdata/return/no_value.carbon
+++ b/toolchain/lower/testdata/return/no_value.carbon
@@ -27,7 +27,7 @@ fn Main() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "no_value.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/return/return_var.carbon b/toolchain/lower/testdata/return/return_var.carbon
index 11534473bcf9..eb0ec185576e 100644
--- a/toolchain/lower/testdata/return/return_var.carbon
+++ b/toolchain/lower/testdata/return/return_var.carbon
@@ -37,7 +37,7 @@ fn Make() -> C {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "return_var.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Make", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Make", linkageName: "Make", scope: null, file: !3, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 18, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/return/return_var_byval.carbon b/toolchain/lower/testdata/return/return_var_byval.carbon
index ebdd4f9fc89c..8a51a51c0d01 100644
--- a/toolchain/lower/testdata/return/return_var_byval.carbon
+++ b/toolchain/lower/testdata/return/return_var_byval.carbon
@@ -31,7 +31,7 @@ fn Main() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "return_var_byval.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 16, scope: !4)
diff --git a/toolchain/lower/testdata/return/value.carbon b/toolchain/lower/testdata/return/value.carbon
index d73bfccad8c1..9acf6aab27e8 100644
--- a/toolchain/lower/testdata/return/value.carbon
+++ b/toolchain/lower/testdata/return/value.carbon
@@ -27,7 +27,7 @@ fn Main() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "value.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/return/var.carbon b/toolchain/lower/testdata/return/var.carbon
index 5e5b4d30d5c1..ff723860a62a 100644
--- a/toolchain/lower/testdata/return/var.carbon
+++ b/toolchain/lower/testdata/return/var.carbon
@@ -31,7 +31,7 @@ fn Main() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "var.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Main", linkageName: "Main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/struct/empty.carbon b/toolchain/lower/testdata/struct/empty.carbon
index 012dfb2bfa08..3cc6457fc6c0 100644
--- a/toolchain/lower/testdata/struct/empty.carbon
+++ b/toolchain/lower/testdata/struct/empty.carbon
@@ -31,7 +31,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "empty.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/struct/member_access.carbon b/toolchain/lower/testdata/struct/member_access.carbon
index 730c5ba41829..c617c889b175 100644
--- a/toolchain/lower/testdata/struct/member_access.carbon
+++ b/toolchain/lower/testdata/struct/member_access.carbon
@@ -48,7 +48,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "member_access.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/struct/nested_struct.carbon b/toolchain/lower/testdata/struct/nested_struct.carbon
index a0b61373089d..aa2a251c0b35 100644
--- a/toolchain/lower/testdata/struct/nested_struct.carbon
+++ b/toolchain/lower/testdata/struct/nested_struct.carbon
@@ -28,7 +28,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "nested_struct.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 13, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/struct/nested_struct_in_place.carbon b/toolchain/lower/testdata/struct/nested_struct_in_place.carbon
index 6f0af8032057..71ce1ebbdf46 100644
--- a/toolchain/lower/testdata/struct/nested_struct_in_place.carbon
+++ b/toolchain/lower/testdata/struct/nested_struct_in_place.carbon
@@ -36,7 +36,7 @@ fn G() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "nested_struct_in_place.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/struct/one_entry.carbon b/toolchain/lower/testdata/struct/one_entry.carbon
index fe2bea180e21..b55ed350498c 100644
--- a/toolchain/lower/testdata/struct/one_entry.carbon
+++ b/toolchain/lower/testdata/struct/one_entry.carbon
@@ -36,7 +36,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "one_entry.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/struct/two_entries.carbon b/toolchain/lower/testdata/struct/two_entries.carbon
index 3da1a1c3aa3b..47a71cb151a3 100644
--- a/toolchain/lower/testdata/struct/two_entries.carbon
+++ b/toolchain/lower/testdata/struct/two_entries.carbon
@@ -49,7 +49,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "two_entries.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/access/element_access.carbon b/toolchain/lower/testdata/tuple/access/element_access.carbon
index f4acdce8a32c..e32c6493211a 100644
--- a/toolchain/lower/testdata/tuple/access/element_access.carbon
+++ b/toolchain/lower/testdata/tuple/access/element_access.carbon
@@ -50,7 +50,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "element_access.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/access/return_value_access.carbon b/toolchain/lower/testdata/tuple/access/return_value_access.carbon
index 62718e8dbe1e..112baa51e642 100644
--- a/toolchain/lower/testdata/tuple/access/return_value_access.carbon
+++ b/toolchain/lower/testdata/tuple/access/return_value_access.carbon
@@ -50,12 +50,12 @@ fn Run() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "return_value_access.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 11, column: 31, scope: !4)
 // CHECK:STDOUT: !8 = !DILocation(line: 11, column: 24, scope: !4)
-// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !10 = !DILocation(line: 14, column: 7, scope: !9)
 // CHECK:STDOUT: !11 = !DILocation(line: 14, column: 16, scope: !9)
 // CHECK:STDOUT: !12 = !DILocation(line: 14, column: 3, scope: !9)
diff --git a/toolchain/lower/testdata/tuple/empty.carbon b/toolchain/lower/testdata/tuple/empty.carbon
index 824b9076ddfe..8a2ddfb3a323 100644
--- a/toolchain/lower/testdata/tuple/empty.carbon
+++ b/toolchain/lower/testdata/tuple/empty.carbon
@@ -31,7 +31,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "empty.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/nested_tuple.carbon b/toolchain/lower/testdata/tuple/nested_tuple.carbon
index 323b35aa51b7..2d7ce3487fab 100644
--- a/toolchain/lower/testdata/tuple/nested_tuple.carbon
+++ b/toolchain/lower/testdata/tuple/nested_tuple.carbon
@@ -28,7 +28,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "nested_tuple.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 13, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon b/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon
index e71eaaaa0eb8..2384cb65bfcf 100644
--- a/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon
+++ b/toolchain/lower/testdata/tuple/nested_tuple_in_place.carbon
@@ -36,7 +36,7 @@ fn G() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "nested_tuple_in_place.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "G", linkageName: "G", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/one_entry.carbon b/toolchain/lower/testdata/tuple/one_entry.carbon
index 099c941b4eba..d75dc9da852e 100644
--- a/toolchain/lower/testdata/tuple/one_entry.carbon
+++ b/toolchain/lower/testdata/tuple/one_entry.carbon
@@ -39,7 +39,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "one_entry.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/two_entries.carbon b/toolchain/lower/testdata/tuple/two_entries.carbon
index c6fce943783e..bbc42fc4e6ea 100644
--- a/toolchain/lower/testdata/tuple/two_entries.carbon
+++ b/toolchain/lower/testdata/tuple/two_entries.carbon
@@ -49,7 +49,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "two_entries.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/value_formation.carbon b/toolchain/lower/testdata/tuple/value_formation.carbon
index 7306d80099f1..d99f713376b0 100644
--- a/toolchain/lower/testdata/tuple/value_formation.carbon
+++ b/toolchain/lower/testdata/tuple/value_formation.carbon
@@ -67,7 +67,7 @@ fn F() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "value_formation.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/tuple/value_forwarding.carbon b/toolchain/lower/testdata/tuple/value_forwarding.carbon
index 11df9e654251..059fcaee7fd9 100644
--- a/toolchain/lower/testdata/tuple/value_forwarding.carbon
+++ b/toolchain/lower/testdata/tuple/value_forwarding.carbon
@@ -37,7 +37,7 @@ fn F(a: (i32, i32, i32), b: (i32, i32, i32)) {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "value_forwarding.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "F", scope: null, file: !3, line: 13, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 14, column: 5, scope: !4)
diff --git a/toolchain/lower/testdata/var/local.carbon b/toolchain/lower/testdata/var/local.carbon
index 51da2872a987..6ceb441c60fc 100644
--- a/toolchain/lower/testdata/var/local.carbon
+++ b/toolchain/lower/testdata/var/local.carbon
@@ -31,7 +31,7 @@ fn Run() -> i32 {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "local.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "Run", linkageName: "main", scope: null, file: !3, line: 11, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 12, column: 7, scope: !4)
diff --git a/toolchain/lower/testdata/while/break_continue.carbon b/toolchain/lower/testdata/while/break_continue.carbon
index f895e23ff4a4..2d7cb52accc0 100644
--- a/toolchain/lower/testdata/while/break_continue.carbon
+++ b/toolchain/lower/testdata/while/break_continue.carbon
@@ -67,7 +67,7 @@ fn While() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "break_continue.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", linkageName: "While", scope: null, file: !3, line: 15, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 16, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/while/preheader.carbon b/toolchain/lower/testdata/while/preheader.carbon
index 5685f67ada90..ba9d51a05fe9 100644
--- a/toolchain/lower/testdata/while/preheader.carbon
+++ b/toolchain/lower/testdata/while/preheader.carbon
@@ -78,7 +78,7 @@ fn While() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "preheader.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", scope: null, file: !3, line: 19, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", linkageName: "While", scope: null, file: !3, line: 19, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 20, column: 10, scope: !4)
diff --git a/toolchain/lower/testdata/while/unreachable_end.carbon b/toolchain/lower/testdata/while/unreachable_end.carbon
index ed09fa84516f..8a50e4bb4e78 100644
--- a/toolchain/lower/testdata/while/unreachable_end.carbon
+++ b/toolchain/lower/testdata/while/unreachable_end.carbon
@@ -59,7 +59,7 @@ fn While() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "unreachable_end.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", linkageName: "While", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 18, column: 3, scope: !4)
diff --git a/toolchain/lower/testdata/while/while.carbon b/toolchain/lower/testdata/while/while.carbon
index ddb102008f18..8708aacd45b4 100644
--- a/toolchain/lower/testdata/while/while.carbon
+++ b/toolchain/lower/testdata/while/while.carbon
@@ -58,7 +58,7 @@ fn While() {
 // CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
 // CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
 // CHECK:STDOUT: !3 = !DIFile(filename: "while.carbon", directory: "")
-// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "While", linkageName: "While", scope: null, file: !3, line: 17, type: !5, spFlags: DISPFlagDefinition, unit: !2)
 // CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
 // CHECK:STDOUT: !6 = !{}
 // CHECK:STDOUT: !7 = !DILocation(line: 18, column: 3, scope: !4)