[llvm] 267ff79 - [SLP] limit verifyFunction to debug build (PR48689)

[Sanjay Patel via llvm-commits]

On Fri, Jan 8, 2021 at 8:19 AM Roman Lebedev <lebedev.ri at gmail.com> wrote:

> On Fri, Jan 8, 2021 at 4:10 PM Sanjay Patel via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
> >
> >
> > Author: Sanjay Patel
> > Date: 2021-01-08T08:10:17-05:00
> > New Revision: 267ff7901c745dc903d55599240464ebc4c0bda3
> >
> > URL:
> https://github.com/llvm/llvm-project/commit/267ff7901c745dc903d55599240464ebc4c0bda3
> > DIFF:
> https://github.com/llvm/llvm-project/commit/267ff7901c745dc903d55599240464ebc4c0bda3.diff
> >
> > LOG: [SLP] limit verifyFunction to debug build (PR48689)
> >
> > As noted in PR48689, the verifier may have some kind
> > of exponential behavior that should be addressed
> > separately. For now, only run it in debug mode to
> > prevent problems for release+asserts.
> > That limit is what we had before D80401, and I'm
> > not sure if there was a reason to change it in that
> > patch.
> >
> > Added:
> >
> >
> > Modified:
> >     llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
> >
> > Removed:
> >
> >
> >
> >
> ################################################################################
> > diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
> b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
> > index 8c06e29341ad..ef0dea0f11d3 100644
> > --- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
> > +++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
> > @@ -2499,7 +2499,7 @@ BoUpSLP::~BoUpSLP() {
> >             "trying to erase instruction with users.");
> >      Pair.getFirst()->eraseFromParent();
> >    }
> > -  assert(!verifyFunction(*F, &dbgs()));
> > +  LLVM_DEBUG(verifyFunction(*F));
> Nitpick: `assert()` already limited the code to debug build only (well,
> -DLLVM_ENABLE_ASSERTIONS=ON) Wrapping it into LLVM_DEBUG()
> made it run wherever `-mllvm -debug-only=SLP` is specified.
>

Yes. IIUC, there's a (potentially large) fraction of LLVM users that build
as release with asserts and expect release-like behavior (good perf), so we
want to maintain that mode of operation. Once we go to "full" debug build,
we give up on any hope of having a useful experience for anything but
full-on (extremely slow) debugging.
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