v.g.vassilev added inline comments.
================
Comment at: clang/lib/CodeGen/CodeGenModule.cpp:2389
if (getTarget().getCXXABI().areMemberFunctionsAligned()) {
- if (F->getPointerAlignment(getDataLayout()) < 2 && isa<CXXMethodDecl>(D))
+ if (isa<CXXMethodDecl>(D) && F->getPointerAlignment(getDataLayout()) < 2)
F->setAlignment(std::max(llvm::Align(2), F->getAlign().valueOrOne()));
----------------
daltenty wrote:
> v.g.vassilev wrote:
> > daltenty wrote:
> > > Thanks for looking into this.
> > >
> > > It's not clear to me how this re-ordering ends up fixing things. Can you
> > > clarify what the uninitialized value was in this expression?
> > >
> > >
> > The issue happens only in Release builds (RelWithDebInfo, too). From what I
> > was able to see it is somewhere in `F->getPointerAlignment`. My assumption
> > was that we cannot rely on the full properties of `F` to be set unless it
> > is the declaration kind we expected (similar to checking if a something is
> > a nullptr and then probing its members). Secondly the `isa` check is likely
> > to be the less expensive check anyway.
> >
> > I saw the issue yesterday and dug into it for a while. However, I decided
> > to insert a "fix" before the release which is in few days since the `isa`
> > seems to the faster check anyway.
> Thanks, yeah thats kind of what I expected. `F->getPointerAlignment()` is
> likely getting inlined into in to this callsite and we are inspecting
> uninitialized properties of the DataLayout. The weird part is I don't see why
> those properties of the DataLayout ever should be uninitialized, so I think
> there might be something more broken underneath this.
>
> That said, this is definitely better than before as you say, so let's go
> ahead with this for the release and maybe I'll do some more digging in
> `getPointerAlignment`.
Sounds good. For better or worse that workaround might make the issue more
subtle to debug next time it appears...
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D159339/new/
https://reviews.llvm.org/D159339
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