Revert rL344933 from llvm/trunk: [X86][SSE] Tidyup DecodeVPERMILPMask shuffle mask decoding

We can't safely assume that certain RawMask entries are UNDEF as most variable shuffles ignore non-index bits.
........
Add support for UNDEF raw mask elements and remove the ConstantPool DecodeVPERMILPMask usage in X86ISelLowering.cpp

llvm-svn: 344936

2 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
index 4bd5df44abd..fe567f4cece 100644
--- a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
+++ b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
@@ -501,10 +501,6 @@ void DecodeVPERMILPMask(unsigned NumElts, unsigned ScalarBits,
 
   for (unsigned i = 0, e = RawMask.size(); i < e; ++i) {
     uint64_t M = RawMask[i];
-    if (M == (uint64_t)SM_SentinelUndef) {
-      ShuffleMask.push_back(M);
-      continue;
-    }
     M = (ScalarBits == 64 ? ((M >> 1) & 0x1) : (M & 0x3));
     unsigned LaneOffset = i & ~(NumEltsPerLane - 1);
     ShuffleMask.push_back((int)(LaneOffset + M));
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index ea95a8aeaea..e2b2191b181 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6043,10 +6043,14 @@ static bool getTargetShuffleMask(SDNode *N, MVT VT, bool AllowSentinelZero,
     IsUnary = true;
     SDValue MaskNode = N->getOperand(1);
     SmallVector<uint64_t, 32> RawMask;
-    if (getTargetShuffleMaskIndices(MaskNode, MaskEltSize, RawMask, true)) {
+    if (getTargetShuffleMaskIndices(MaskNode, MaskEltSize, RawMask)) {
       DecodeVPERMILPMask(NumElems, MaskEltSize, RawMask, Mask);
       break;
     }
+    if (auto *C = getTargetConstantFromNode(MaskNode)) {
+      DecodeVPERMILPMask(C, MaskEltSize, Mask);
+      break;
+    }
     return false;
   }
   case X86ISD::PSHUFB: {