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Fix mangling collision for C++ class template specializations (#7269)

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Carbon-side thunks (for example the `Copy`/`Destroy` witness thunks
generated for imported C++ types) are mangled by Carbon, and their names
incorporate a fingerprint of the involved types. The instruction
fingerprinter identifies a class only by its name and parent scope,
which is sufficient for Carbon classes but not for imported C++ classes:
different specializations of one class template (and other cases such as
types in anonymous namespaces) share a Carbon name and parent scope. As
a result, the thunks for two distinct specializations could mangle to
the same name, producing a single LLVM function with two definitions and
failing `verifyModule` during lowering.

When fingerprinting a class imported from C++, also include the Clang
mangled name of its type.

Test: toolchain/lower/testdata/interop/cpp/thunks.carbon gains a split
with two specializations of one class template, each requiring a thunk;
their thunks now get distinct mangled names instead of colliding.

Assisted-by: Claude Code

---------

Co-authored-by: Christopher Di Bella <cjdb.ns@gmail.com>
This commit is contained in:
Chandler Carruth
2026-05-30 08:13:00 +00:00
committed by GitHub
co-authored by Christopher Di Bella
parent 3ef128ac91
commit 8a59f2a76b
64 changed files with 4762 additions and 4330 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/lower/testdata/interop/cpp/constructor.carbon
Vendored
+20 -20
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@@ -281,7 +281,7 @@ fn Four() {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %_.var = alloca [8 x i8], align 1, !dbg !14
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %_.var), !dbg !14
// CHECK:STDOUT: call void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.2603c91dd66a1dca"(ptr %_.var), !dbg !14
// CHECK:STDOUT: call void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.4fdc745d4b6d0e3c"(ptr %_.var), !dbg !14
// CHECK:STDOUT: ret void, !dbg !15
// CHECK:STDOUT: }
// CHECK:STDOUT:
@@ -296,7 +296,7 @@ fn Four() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_COp:thunk:Default.5648bcc2d6c775b7.Core:C.Cpp"(ptr sret([8 x i8]) %return) #2 !dbg !19 {
// CHECK:STDOUT: define void @"_COp:thunk:Default.08e786f435a99766.Core:C.Cpp"(ptr sret([8 x i8]) %return) #2 !dbg !19 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @_ZN1CC1Ev.carbon_thunk.(ptr %return), !dbg !24
// CHECK:STDOUT: ret void, !dbg !24
@@ -306,8 +306,8 @@ fn Four() {
// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #3
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.2603c91dd66a1dca"(ptr sret([8 x i8]) %return) #0 !dbg !25 {
// CHECK:STDOUT: call void @"_COp:thunk:Default.5648bcc2d6c775b7.Core:C.Cpp"(ptr %return), !dbg !27
// CHECK:STDOUT: define linkonce_odr void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.4fdc745d4b6d0e3c"(ptr sret([8 x i8]) %return) #0 !dbg !25 {
// CHECK:STDOUT: call void @"_COp:thunk:Default.08e786f435a99766.Core:C.Cpp"(ptr %return), !dbg !27
// CHECK:STDOUT: ret void, !dbg !28
// CHECK:STDOUT: }
// CHECK:STDOUT:
@@ -353,13 +353,13 @@ fn Four() {
// CHECK:STDOUT: !16 = !{!17, !17, i64 0}
// CHECK:STDOUT: !17 = !{!"p1 _ZTS1C", !18, i64 0}
// CHECK:STDOUT: !18 = !{!"any pointer", !9, i64 0}
// CHECK:STDOUT: !19 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.5648bcc2d6c775b7.Core:C.Cpp", scope: null, file: !20, line: 4, type: !21, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !19 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.08e786f435a99766.Core:C.Cpp", scope: null, file: !20, line: 4, type: !21, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !20 = !DIFile(filename: "./default.h", directory: "")
// CHECK:STDOUT: !21 = !DISubroutineType(types: !22)
// CHECK:STDOUT: !22 = !{!23}
// CHECK:STDOUT: !23 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
// CHECK:STDOUT: !24 = !DILocation(line: 4, column: 3, scope: !19)
// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "Op", linkageName: "_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.2603c91dd66a1dca", scope: null, file: !26, line: 9, type: !21, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "Op", linkageName: "_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.4fdc745d4b6d0e3c", scope: null, file: !26, line: 9, type: !21, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !26 = !DIFile(filename: "min_prelude/parts/default.carbon", directory: "")
// CHECK:STDOUT: !27 = !DILocation(line: 9, column: 28, scope: !25)
// CHECK:STDOUT: !28 = !DILocation(line: 9, column: 21, scope: !25)
@@ -388,11 +388,11 @@ fn Four() {
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %.loc8_65.1.temp), !dbg !14
// CHECK:STDOUT: call void @_ZN26ImplicitlyDefaultedDefaultC1Ev.carbon_thunk.(ptr %.loc8_65.1.temp), !dbg !14
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %_.var.loc9), !dbg !15
// CHECK:STDOUT: call void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.2db09a503899761f"(ptr %_.var.loc9), !dbg !15
// CHECK:STDOUT: call void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.dc183edbabc24d2f"(ptr %_.var.loc9), !dbg !15
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %.loc12_65.1.temp), !dbg !16
// CHECK:STDOUT: call void @_ZN26ExplicitlyDefaultedDefaultC1Ev.carbon_thunk.(ptr %.loc12_65.1.temp), !dbg !16
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %_.var.loc13), !dbg !17
// CHECK:STDOUT: call void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.0dfbcd9a7c1791ba"(ptr %_.var.loc13), !dbg !17
// CHECK:STDOUT: call void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.44ad2ae60410d16d"(ptr %_.var.loc13), !dbg !17
// CHECK:STDOUT: ret void, !dbg !18
// CHECK:STDOUT: }
// CHECK:STDOUT:
@@ -407,7 +407,7 @@ fn Four() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_COp:thunk:Default.40902cf3dea87d9c.Core:ImplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !22 {
// CHECK:STDOUT: define void @"_COp:thunk:Default.1458cb9e3f45d9d7.Core:ImplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !22 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @_ZN26ImplicitlyDefaultedDefaultC1Ev.carbon_thunk.(ptr %return), !dbg !27
// CHECK:STDOUT: ret void, !dbg !27
@@ -424,7 +424,7 @@ fn Four() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_COp:thunk:Default.f7ced4a20f885cf5.Core:ExplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !30 {
// CHECK:STDOUT: define void @"_COp:thunk:Default.16c8d515df1b6c01.Core:ExplicitlyDefaultedDefault.Cpp"(ptr sret([4 x i8]) %return) #2 !dbg !30 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @_ZN26ExplicitlyDefaultedDefaultC1Ev.carbon_thunk.(ptr %return), !dbg !31
// CHECK:STDOUT: ret void, !dbg !31
@@ -434,14 +434,14 @@ fn Four() {
// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #3
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.2db09a503899761f"(ptr sret([4 x i8]) %return) #0 !dbg !32 {
// CHECK:STDOUT: call void @"_COp:thunk:Default.40902cf3dea87d9c.Core:ImplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !34
// CHECK:STDOUT: define linkonce_odr void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.dc183edbabc24d2f"(ptr sret([4 x i8]) %return) #0 !dbg !32 {
// CHECK:STDOUT: call void @"_COp:thunk:Default.1458cb9e3f45d9d7.Core:ImplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !34
// CHECK:STDOUT: ret void, !dbg !35
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.0dfbcd9a7c1791ba"(ptr sret([4 x i8]) %return) #0 !dbg !36 {
// CHECK:STDOUT: call void @"_COp:thunk:Default.f7ced4a20f885cf5.Core:ExplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !37
// CHECK:STDOUT: define linkonce_odr void @"_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.44ad2ae60410d16d"(ptr sret([4 x i8]) %return) #0 !dbg !36 {
// CHECK:STDOUT: call void @"_COp:thunk:Default.16c8d515df1b6c01.Core:ExplicitlyDefaultedDefault.Cpp"(ptr %return), !dbg !37
// CHECK:STDOUT: ret void, !dbg !38
// CHECK:STDOUT: }
// CHECK:STDOUT:
@@ -503,7 +503,7 @@ fn Four() {
// CHECK:STDOUT: !19 = !{!20, !20, i64 0}
// CHECK:STDOUT: !20 = !{!"p1 _ZTS26ImplicitlyDefaultedDefault", !21, i64 0}
// CHECK:STDOUT: !21 = !{!"any pointer", !9, i64 0}
// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.40902cf3dea87d9c.Core:ImplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 2, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.1458cb9e3f45d9d7.Core:ImplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 2, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !23 = !DIFile(filename: "./defaulted_default.h", directory: "")
// CHECK:STDOUT: !24 = !DISubroutineType(types: !25)
// CHECK:STDOUT: !25 = !{!26}
@@ -511,13 +511,13 @@ fn Four() {
// CHECK:STDOUT: !27 = !DILocation(line: 2, column: 8, scope: !22)
// CHECK:STDOUT: !28 = !{!29, !29, i64 0}
// CHECK:STDOUT: !29 = !{!"p1 _ZTS26ExplicitlyDefaultedDefault", !21, i64 0}
// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.f7ced4a20f885cf5.Core:ExplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 7, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !30 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Default.16c8d515df1b6c01.Core:ExplicitlyDefaultedDefault.Cpp", scope: null, file: !23, line: 7, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !31 = !DILocation(line: 7, column: 3, scope: !30)
// CHECK:STDOUT: !32 = distinct !DISubprogram(name: "Op", linkageName: "_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.2db09a503899761f", scope: null, file: !33, line: 9, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !32 = distinct !DISubprogram(name: "Op", linkageName: "_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.dc183edbabc24d2f", scope: null, file: !33, line: 9, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !33 = !DIFile(filename: "min_prelude/parts/default.carbon", directory: "")
// CHECK:STDOUT: !34 = !DILocation(line: 9, column: 28, scope: !32)
// CHECK:STDOUT: !35 = !DILocation(line: 9, column: 21, scope: !32)
// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "Op", linkageName: "_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.0dfbcd9a7c1791ba", scope: null, file: !33, line: 9, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !36 = distinct !DISubprogram(name: "Op", linkageName: "_COp.cbe5dd53b28eb3d1:DefaultOrUnformed.Core.44ad2ae60410d16d", scope: null, file: !33, line: 9, type: !24, spFlags: DISPFlagDefinition, unit: !5)
// CHECK:STDOUT: !37 = !DILocation(line: 9, column: 28, scope: !36)
// CHECK:STDOUT: !38 = !DILocation(line: 9, column: 21, scope: !36)
// CHECK:STDOUT: !39 = !{!40, !8, i64 0}
@@ -552,7 +552,7 @@ fn Four() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_COp:thunk:Copy.83073f2d17ed2f9e.Core:Copy.Cpp"(ptr sret([4 x i8]) %return, ptr %self) #2 !dbg !22 {
// CHECK:STDOUT: define void @"_COp:thunk:Copy.0459c72f2d146eb1.Core:Copy.Cpp"(ptr sret([4 x i8]) %return, ptr %self) #2 !dbg !22 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @_ZN4CopyC1ERKS_.carbon_thunk._(ptr %self, ptr %return), !dbg !26
// CHECK:STDOUT: ret void, !dbg !26
@@ -595,7 +595,7 @@ fn Four() {
// CHECK:STDOUT: !19 = !{!20, !20, i64 0}
// CHECK:STDOUT: !20 = !{!"p1 _ZTS4Copy", !21, i64 0}
// CHECK:STDOUT: !21 = !{!"any pointer", !9, i64 0}
// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Copy.83073f2d17ed2f9e.Core:Copy.Cpp", scope: null, file: !23, line: 5, type: !12, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !24)
// CHECK:STDOUT: !22 = distinct !DISubprogram(name: "Op", linkageName: "_COp:thunk:Copy.0459c72f2d146eb1.Core:Copy.Cpp", scope: null, file: !23, line: 5, type: !12, spFlags: DISPFlagDefinition, unit: !5, retainedNodes: !24)
// CHECK:STDOUT: !23 = !DIFile(filename: "./copy.h", directory: "")
// CHECK:STDOUT: !24 = !{!25}
// CHECK:STDOUT: !25 = !DILocalVariable(arg: 1, scope: !22, type: !14)