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Give thunks weak_odr linkage. (#7525)

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We can end up emitting the same thunk from multiple compilations in some
cases -- in particular, when the thunk is wrapping a function that is
either synthesized by the compiler or imported from C++. When this
happens, we will have multiple-definition link errors unless we allow
redefinitions across multiple files.

It'd be nice to detect when we need to do this and when we don't, but
that's a bit tricky to do in practice. Ideally, in fact, we would use a
different strategy, and emit the thunks as discardable definitions in
each compilation that *uses* them. But for now emitting them with
weak_odr linkage seems like a good way to make progress.
This commit is contained in:
Richard Smith
2026-07-17 13:25:19 +00:00
committed by GitHub
parent 643ab57f5a
commit 5c544f7c2f
20 changed files with 362 additions and 75 deletions
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toolchain/lower/testdata/interop/cpp/class/export/class.carbon
Vendored
+4 -4
View File
@@ -274,7 +274,7 @@ fn G() {
// CHECK:STDOUT: declare void @_CCallC.Main(ptr)
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #4 !dbg !19 {
// CHECK:STDOUT: define weak_odr void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #4 !dbg !19 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_COp.68011419f123494e:core.Destroy.Core"(ptr %self), !dbg !25
// CHECK:STDOUT: ret void, !dbg !25
@@ -307,7 +307,7 @@ fn G() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_C__destroy_thunk:thunk.B.Main"(ptr %self) #4 !dbg !45 {
// CHECK:STDOUT: define weak_odr void @"_C__destroy_thunk:thunk.B.Main"(ptr %self) #4 !dbg !45 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_COp.6c3865e9cbd9f6de:core.Destroy.Core"(ptr %self), !dbg !48
// CHECK:STDOUT: ret void, !dbg !48
@@ -334,7 +334,7 @@ fn G() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_C__destroy_thunk:thunk.C.Main"(ptr %self) #4 !dbg !61 {
// CHECK:STDOUT: define weak_odr void @"_C__destroy_thunk:thunk.C.Main"(ptr %self) #4 !dbg !61 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_COp.807eb4f2d3ed7e54:core.Destroy.Core"(ptr %self), !dbg !64
// CHECK:STDOUT: ret void, !dbg !64
@@ -477,7 +477,7 @@ fn G() {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_C__destroy_thunk:thunk.C.Main"(ptr %self) #1 !dbg !20 {
// CHECK:STDOUT: define weak_odr void @"_C__destroy_thunk:thunk.C.Main"(ptr %self) #1 !dbg !20 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_COp.807eb4f2d3ed7e54:core.Destroy.Core"(ptr %self), !dbg !26
// CHECK:STDOUT: ret void, !dbg !26
toolchain/lower/testdata/interop/cpp/class/export/method.carbon
Vendored
+3 -3
View File
@@ -117,7 +117,7 @@ fn CallCallF() { Cpp.CallF(); }
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #5 !dbg !22 {
// CHECK:STDOUT: define weak_odr void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #5 !dbg !22 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_COp.68011419f123494e:core.Destroy.Core"(ptr %self), !dbg !25
// CHECK:STDOUT: ret void, !dbg !25
@@ -240,7 +240,7 @@ fn CallCallF() { Cpp.CallF(); }
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #5 !dbg !25 {
// CHECK:STDOUT: define weak_odr void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #5 !dbg !25 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_COp.68011419f123494e:core.Destroy.Core"(ptr %self), !dbg !30
// CHECK:STDOUT: ret void, !dbg !30
@@ -355,7 +355,7 @@ fn CallCallF() { Cpp.CallF(); }
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #3 !dbg !16 {
// CHECK:STDOUT: define weak_odr void @"_C__destroy_thunk:thunk.A.Main"(ptr %self) #3 !dbg !16 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_COp.68011419f123494e:core.Destroy.Core"(ptr %self), !dbg !22
// CHECK:STDOUT: ret void, !dbg !22