[llvm] 8680dd5 - [X86] getFauxShuffle - don't assume an UNDEF src element for AND/ANDNP results in an UNDEF shuffle mask index

[Simon Pilgrim via llvm-commits]

Author: Simon Pilgrim
Date: 2022-04-28T11:54:31+01:00
New Revision: 8680dd5117b0c36f807fecc4360122ae1dd73b6d

URL: https://github.com/llvm/llvm-project/commit/8680dd5117b0c36f807fecc4360122ae1dd73b6d
DIFF: https://github.com/llvm/llvm-project/commit/8680dd5117b0c36f807fecc4360122ae1dd73b6d.diff

LOG: [X86] getFauxShuffle - don't assume an UNDEF src element for AND/ANDNP results in an UNDEF shuffle mask index

The other src element might be zero, guaranteeing zero.

Fixes #55157

Added: 
    

Modified: 
    llvm/test/CodeGen/X86/vector-shuffle-combining.ll

Removed: 
    


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diff  --git a/llvm/test/CodeGen/X86/vector-shuffle-combining.ll b/llvm/test/CodeGen/X86/vector-shuffle-combining.ll
index d5460297f8be..97bac151d30c 100644
--- a/llvm/test/CodeGen/X86/vector-shuffle-combining.ll
+++ b/llvm/test/CodeGen/X86/vector-shuffle-combining.ll
@@ -3333,11 +3333,17 @@ define void @PR45604(<32 x i16>* %dst, <8 x i16>* %src) {
   ret void
 }
 
-; FIXME: getFauxShuffle AND/ANDN decoding wrongly assumes an undef src always gives an undef dst.
+; getFauxShuffle AND/ANDN decoding wrongly assumed an undef src always gives an undef dst.
 define <2 x i64> @PR55157(<16 x i8>* %0) {
-; CHECK-LABEL: PR55157:
-; CHECK:       # %bb.0:
-; CHECK-NEXT:    retq
+; SSE-LABEL: PR55157:
+; SSE:       # %bb.0:
+; SSE-NEXT:    xorps %xmm0, %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: PR55157:
+; AVX:       # %bb.0:
+; AVX-NEXT:    vxorps %xmm0, %xmm0, %xmm0
+; AVX-NEXT:    retq
   %2 = load <16 x i8>, <16 x i8>* %0, align 16
   %3 = icmp eq <16 x i8> %2, zeroinitializer
   %4 = tail call <16 x i8> @llvm.x86.sse2.pavg.b(<16 x i8> zeroinitializer, <16 x i8> zeroinitializer)