[X86][SSE] Fix an issue with PEXTRW/PEXTRB indices during shuffle combining

We were checking that the index was in range of the destination vector type, not the (larger) source vector type

llvm-svn: 304894

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 048fc29660e..246f2e91eb7 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -5868,8 +5868,7 @@ static bool getFauxShuffleMask(SDValue N, SmallVectorImpl<int> &Mask,
       assert(SrcExtract.getOperand(0).getValueType() == MVT::v16i8);
     }
 
-    if (!SrcExtract || !isa<ConstantSDNode>(SrcExtract.getOperand(1)) ||
-        NumElts <= SrcExtract.getConstantOperandVal(1))
+    if (!SrcExtract || !isa<ConstantSDNode>(SrcExtract.getOperand(1)))
       return false;
 
     SDValue SrcVec = SrcExtract.getOperand(0);
@@ -5877,8 +5876,12 @@ static bool getFauxShuffleMask(SDValue N, SmallVectorImpl<int> &Mask,
     unsigned NumSrcElts = SrcVT.getVectorNumElements();
     unsigned NumZeros = (NumBitsPerElt / SrcVT.getScalarSizeInBits()) - 1;
 
+    unsigned SrcIdx = SrcExtract.getConstantOperandVal(1);
+    if (NumSrcElts <= SrcIdx)
+      return false;
+
     Ops.push_back(SrcVec);
-    Mask.push_back(SrcExtract.getConstantOperandVal(1));
+    Mask.push_back(SrcIdx);
     Mask.append(NumZeros, SM_SentinelZero);
     Mask.append(NumSrcElts - Mask.size(), SM_SentinelUndef);
     return true;