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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/impl/import_thunk.carbon
Vendored
+2 -2
View File
@@ -101,7 +101,7 @@ fn Test(a: A) -> C {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_CF:thunk:I.4b54445be9b10a0e.Main:61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
// CHECK:STDOUT: define weak_odr void @"_CF:thunk:I.4b54445be9b10a0e.Main:61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %.loc20_19.1.temp = alloca { i32 }, align 4, !dbg !28
// CHECK:STDOUT: %.4.temp = alloca { i32 }, align 4, !dbg !29
@@ -301,7 +301,7 @@ fn Test(a: A) -> C {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_CF:thunk:I.c81631f865470482.Main:X.Main:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !13 {
// CHECK:STDOUT: define weak_odr void @"_CF:thunk:I.c81631f865470482.Main:X.Main:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !13 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %.loc9_19.1.temp = alloca { i32 }, align 4, !dbg !16
// CHECK:STDOUT: %.4.temp = alloca { i32 }, align 4, !dbg !17
toolchain/lower/testdata/impl/thunk.carbon
Vendored
+1 -1
View File
@@ -105,7 +105,7 @@ fn CallCallGeneric(c: C(()), b: B) -> A {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline nounwind
// CHECK:STDOUT: define void @"_CF:thunk:I.4b54445be9b10a0e.Main:61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
// CHECK:STDOUT: define weak_odr void @"_CF:thunk:I.4b54445be9b10a0e.Main:61ea2aba74ab3bf1:I.Main"(ptr sret({ i32 }) %return, ptr %a) #1 !dbg !25 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %.loc20_19.1.temp = alloca { i32 }, align 4, !dbg !28
// CHECK:STDOUT: %.4.temp = alloca { i32 }, align 4, !dbg !29