fhahn added inline comments.
================
Comment at: clang/lib/CodeGen/CGCall.cpp:2535
ArgAttrs[FirstIRArg + i] =
llvm::AttributeSet::get(getLLVMContext(), Attrs);
}
----------------
nlopes wrote:
> fhahn wrote:
> > nlopes wrote:
> > > ab wrote:
> > > > Hmm, if I'm reading this right, this overwrites the `nonnull
> > > > dereferenceable align` attributes separately computed for `this` around
> > > > l2335, right? (or `inalloca` and `sret` before that)
> > > >
> > > > It sounds like an ancient bug, that's only exposed because `noundef`
> > > > ends up triggering this logic much more often?
> > > >
> > > > Many of our downstream tests hit this. The hacked up patch seems to do
> > > > the job; ideally we'd feed the previously-computed attrs when
> > > > constructing the AttrBuilder (which would also fix the padding
> > > > argument), but we'd need to match up the IR args first. Maybe that's
> > > > fine as a special-case for arg 0 though
> > > nice catch! It's an ancient bug where arg 0 is overwritten.
> > Is anybody looking into a fix or should we revert the patch until this can
> > be properly addressed?
> I would recommend against reverting this patch because of all the followup
> patches. There were quite a few commits afterwards plus fixes to buildbot
> configurations, so it's a non-trivial overhead to revert everything.
> I was assuming @ab would fix it as he already root-caused the bug..
FWIW it seems a bit unfortunate that there are some clear regressions when the
tests got update, e.g.
https://github.com/llvm/llvm-project/commit/1b1c8d83d3567a60280291c0adb95d1d60335509#diff-7e80d593f26f6f6fb24765c6a169884d7350685d565ee970b0a7b9abaf0fb205L355
I'll work with @ab to fix this though rather than reverting, because another
revert would cause even more conflicts for us downstream.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D105169/new/
https://reviews.llvm.org/D105169
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
