jyknight added a comment.
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
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