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Import C++ vtables (#7174)

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This correctly renders the vtable in SemIR, including allowing overrides
in
Carbon-derived-from-C++ classes.

It doesn't work in lowering because clang walks the methods of the
CXXRecordDecl - and we currently don't export anything into the
CXXRecordDecl's methods (we do export the fields) - so that's next.

This also doesn't teach Clang to affirmatively emit the vtable
regardless of the types use in C++ code - or to have Carbon use the
vtable in an object's initialization.
This commit is contained in:
David Blaikie
2026-05-11 17:33:08 +00:00
committed by GitHub
parent 0f5de499d6
commit df8b25522e
8 changed files with 508 additions and 46 deletions
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toolchain/lower/testdata/interop/cpp/method.carbon
Vendored
+16 -6
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@@ -90,8 +90,12 @@ fn Call(n: Cpp.NeedThunk) {
// CHECK:STDOUT: ret i32 %by_val__carbon_thunk.call, !dbg !19
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: declare void @_ZN4Base5virt0Ev(ptr noundef nonnull align 8 dereferenceable(8)) unnamed_addr #1
// CHECK:STDOUT:
// CHECK:STDOUT: declare void @_ZN1A5virt1Ev(ptr noundef nonnull align 8 dereferenceable(12)) unnamed_addr #1
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: alwaysinline mustprogress uwtable
// CHECK:STDOUT: define internal noundef i32 @_ZNK1A6by_valEv.carbon_thunk(ptr noundef nonnull align 8 dereferenceable(12) %this) #1 {
// CHECK:STDOUT: define internal noundef i32 @_ZNK1A6by_valEv.carbon_thunk(ptr noundef nonnull align 8 dereferenceable(12) %this) #2 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %this.addr = alloca ptr, align 8
// CHECK:STDOUT: store ptr %this, ptr %this.addr, align 8, !tbaa !20
@@ -101,7 +105,7 @@ fn Call(n: Cpp.NeedThunk) {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: mustprogress nounwind uwtable
// CHECK:STDOUT: define linkonce_odr dso_local noundef i32 @_ZNK1A6by_valEv(ptr noundef nonnull align 8 dereferenceable(12) %this) #2 comdat align 2 {
// CHECK:STDOUT: define linkonce_odr dso_local noundef i32 @_ZNK1A6by_valEv(ptr noundef nonnull align 8 dereferenceable(12) %this) #3 comdat align 2 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %this.addr = alloca ptr, align 8
// CHECK:STDOUT: store ptr %this, ptr %this.addr, align 8, !tbaa !20
@@ -112,8 +116,9 @@ fn Call(n: Cpp.NeedThunk) {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nounwind }
// CHECK:STDOUT: attributes #1 = { alwaysinline mustprogress uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT: attributes #2 = { mustprogress nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT: attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT: attributes #2 = { alwaysinline mustprogress uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT: attributes #3 = { mustprogress nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.module.flags = !{!0, !1, !2, !3, !4}
// CHECK:STDOUT: !llvm.dbg.cu = !{!5}
@@ -164,8 +169,12 @@ fn Call(n: Cpp.NeedThunk) {
// CHECK:STDOUT: ret i32 %A.by_ref.call, !dbg !19
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: declare void @_ZN4Base5virt0Ev(ptr noundef nonnull align 8 dereferenceable(8)) unnamed_addr #1
// CHECK:STDOUT:
// CHECK:STDOUT: declare void @_ZN1A5virt1Ev(ptr noundef nonnull align 8 dereferenceable(12)) unnamed_addr #1
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: mustprogress nounwind uwtable
// CHECK:STDOUT: define linkonce_odr dso_local noundef i32 @_ZN1A6by_refEv(ptr noundef nonnull align 8 dereferenceable(12) %this) #1 comdat align 2 {
// CHECK:STDOUT: define linkonce_odr dso_local noundef i32 @_ZN1A6by_refEv(ptr noundef nonnull align 8 dereferenceable(12) %this) #2 comdat align 2 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %this.addr = alloca ptr, align 8
// CHECK:STDOUT: store ptr %this, ptr %this.addr, align 8, !tbaa !20
@@ -176,7 +185,8 @@ fn Call(n: Cpp.NeedThunk) {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nounwind }
// CHECK:STDOUT: attributes #1 = { mustprogress nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT: attributes #1 = { "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT: attributes #2 = { mustprogress nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.module.flags = !{!0, !1, !2, !3, !4}
// CHECK:STDOUT: !llvm.dbg.cu = !{!5}