[X86][SSE] Fold movmsk(not(x)) -> not(movmsk)

Helps to improve folding of comparisons with movmsk results.

llvm-svn: 361056

1 files changed, 14 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 743e23977e5..4787741cb9b 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -41498,6 +41498,8 @@ static SDValue combineMOVMSK(SDNode *N, SelectionDAG &DAG,
   SDValue Src = N->getOperand(0);
   MVT SrcVT = Src.getSimpleValueType();
   MVT VT = N->getSimpleValueType(0);
+  unsigned NumBits = VT.getScalarSizeInBits();
+  unsigned NumElts = SrcVT.getVectorNumElements();
 
   // Perform constant folding.
   if (ISD::isBuildVectorOfConstantSDNodes(Src.getNode())) {
@@ -41517,9 +41519,20 @@ static SDValue combineMOVMSK(SDNode *N, SelectionDAG &DAG,
       Src.getOperand(0).getScalarValueSizeInBits() == EltWidth)
     return DAG.getNode(X86ISD::MOVMSK, SDLoc(N), VT, Src.getOperand(0));
 
+  // Fold movmsk(not(x)) -> not(movmsk) to improve folding of movmsk results
+  // with scalar comparisons.
+  if (SDValue NotSrc = IsNOT(Src, DAG)) {
+    SDLoc DL(N);
+    APInt NotMask = APInt::getLowBitsSet(NumBits, NumElts);
+    NotSrc = DAG.getBitcast(SrcVT, NotSrc);
+    return DAG.getNode(ISD::XOR, DL, VT,
+                       DAG.getNode(X86ISD::MOVMSK, DL, VT, NotSrc),
+                       DAG.getConstant(NotMask, DL, VT));
+  }
+
   // Simplify the inputs.
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
-  APInt DemandedMask(APInt::getAllOnesValue(VT.getScalarSizeInBits()));
+  APInt DemandedMask(APInt::getAllOnesValue(NumBits));
   if (TLI.SimplifyDemandedBits(SDValue(N, 0), DemandedMask, DCI))
     return SDValue(N, 0);