lebedev.ri added a subscriber: aaron.ballman. lebedev.ri added a comment. ping @rsmith @rjmccall @aaron.ballman
To spell this out explicitly: i'm afraid i'm not really sure how to fix this preexisting thunk irgen bug. I think it should be fixed in `CodeGenVTables::maybeEmitThunk()`, likely in `arrangeGlobalDeclaration()`. Or is this wrong on the AST level, too? In D99790#2680857 <https://reviews.llvm.org/D99790#2680857>, @jyknight wrote: > It seems like there's a bug with vtable thunks getting the wrong information. > This appears to be a pre-existing bug, but this change has caused it to start > actively breaking code. > > Test case: > > class Base1 { > virtual void Foo1(); > }; > > class Base2 { > virtual void Foo2(); > }; > > class alignas(16) Obj : public Base1, public Base2 { > void Foo1() override; > void Foo2() override; > ~Obj(); > }; > > void Obj::Foo1() {} > void Obj::Foo2() {} > > emits three method definitions: > > define dso_local void @_ZN3Obj4Foo1Ev(%class.Obj* nonnull align 16 > dereferenceable(16) %0) unnamed_addr #0 align 2 !dbg !7 { > define dso_local void @_ZN3Obj4Foo2Ev(%class.Obj* nonnull align 16 > dereferenceable(16) %0) unnamed_addr #0 align 2 !dbg !25 { > define dso_local void @_ZThn8_N3Obj4Foo2Ev(%class.Obj* nonnull align 16 > dereferenceable(16) %0) unnamed_addr #2 align 2 !dbg !29 { > > (See https://godbolt.org/z/MxhYMe1q7, for now at least) > > That third method declaration is bogus -- its argument is _not_ an `Obj*` at > all! In fact, it's pointing at `Obj + 8` -- at the embedded `Base2` object! > As such, `align 16` is incorrect, as is `dereferenceable(16)`. The additional > 8 bytes of dereferenceable claim apparently hasn't broken anything > noticeable, but the alignment claim is causing actual trouble. > > As such, I suggest to revert this change, separately commit a fix to that > underlying bug, and then re-submit this change after that. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D99790/new/ https://reviews.llvm.org/D99790 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
