[llvm-bugs] [Bug 51988] New: AVX-512F intrinsics do not respect masking: _mm512_mask_mul_pd (-ftrapping-math)

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https://bugs.llvm.org/show_bug.cgi?id=51988

            Bug ID: 51988
           Summary: AVX-512F intrinsics do not respect masking:
                    _mm512_mask_mul_pd (-ftrapping-math)
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: florian_hahn at apple.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

AVX-512F has intrinsics that are suppose to mask off lanes for an operation. 
The masking is required to avoid out-of-bounds as well as other failures like
divide-by-zero or invalid FP exceptions.

Clang generates invalid code for these masked intrinsics. It generates an
unmasked multiply followed by a select in IR (also see
https://godbolt.org/z/dsdG6vnM7):

#include <immintrin.h>

__m512d test(__mmask8 mask,  __m512d a,  __m512d b,  __m512d c){
    return _mm512_mask_mul_pd(a, mask, b, c);
}


generates the IR below with `clang -emit-llvm -g0 -O3 -ftrapping-math  -mavx2
-mavx512f`


define dso_local <8 x double> @test(i8 zeroext %0, <8 x double> %1, <8 x
double> %2, <8 x double> %3) local_unnamed_addr #0 {
  %5 = tail call <8 x double> @llvm.experimental.constrained.fmul.v8f64(<8 x
double> %2, <8 x double> %3, metadata !"round.tonearest", metadata
!"fpexcept.strict") #2
  %6 = bitcast i8 %0 to <8 x i1>
  %7 = select <8 x i1> %6, <8 x double> %5, <8 x double> %1
  ret <8 x double> %7
}

declare <8 x double> @llvm.experimental.constrained.fmul.v8f64(<8 x double>, <8
x double>, metadata, metadata) #1


define dso_local <8 x double> @test(i8 zeroext %0, <8 x double> %1, <8 x
double> %2, <8 x double> %3) local_unnamed_addr #0 {
  %5 = tail call <8 x double> @llvm.experimental.constrained.fmul.v8f64(<8 x
double> %2, <8 x double> %3, metadata !"round.tonearest", metadata
!"fpexcept.strict") #2
  %6 = bitcast i8 %0 to <8 x i1>
  %7 = select <8 x i1> %6, <8 x double> %5, <8 x double> %1
  ret <8 x double> %7
}

declare <8 x double> @llvm.experimental.constrained.fmul.v8f64(<8 x double>, <8
x double>, metadata, metadata) #1

attributes #0 = { mustprogress nofree nosync nounwind strictfp uwtable
willreturn "frame-pointer"="none" "min-legal-vector-width"="512"
"stack-protector-buffer-size"="8" "strictfp" "target-cpu"="x86-64"
"target-features"="+avx,+avx2,+avx512f,+crc32,+cx8,+f16c,+fma,+fxsr,+mmx,+popcnt,+sse,+sse2,+sse3,+sse4.1,+sse4.2,+ssse3,+x87,+xsave"
"tune-cpu"="generic" }
attributes #1 = { inaccessiblememonly mustprogress nofree nosync nounwind
willreturn }
attributes #2 = { nounwind strictfp }

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