[X86][SSE] Add SimplifyDemandedBitsForTargetNode handling for MOVMSK

Moves existing SimplifyDemandedBits call out of combineMOVMSK and add SimplifyDemandedVectorElts call based on the sign bits we need.

llvm-svn: 348282

2 files changed, 40 insertions, 8 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index bd069534901..436ee4c4205 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -32466,6 +32466,39 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
     }
     break;
   }
+  case X86ISD::MOVMSK: {
+    SDValue Src = Op.getOperand(0);
+    MVT VT = Op.getSimpleValueType();
+    MVT SrcVT = Src.getSimpleValueType();
+    unsigned SrcBits = SrcVT.getScalarSizeInBits();
+    unsigned NumElts = SrcVT.getVectorNumElements();
+
+    // If we don't need the sign bits at all just return zero.
+    if (OriginalDemandedBits.countTrailingZeros() >= NumElts)
+      return TLO.CombineTo(Op, TLO.DAG.getConstant(0, SDLoc(Op), VT));
+
+    // Only demand the vector elements of the sign bits we need.
+    APInt KnownUndef, KnownZero;
+    APInt DemandedElts = OriginalDemandedBits.zextOrTrunc(NumElts);
+    if (SimplifyDemandedVectorElts(Src, DemandedElts, KnownUndef, KnownZero,
+                                   TLO, Depth + 1))
+      return true;
+
+    Known.Zero = KnownZero.zextOrSelf(BitWidth);
+    Known.Zero.setHighBits(BitWidth - NumElts);
+
+    // MOVMSK only uses the MSB from each vector element.
+    KnownBits KnownSrc;
+    if (SimplifyDemandedBits(Src, APInt::getSignMask(SrcBits), KnownSrc, TLO,
+                             Depth + 1))
+      return true;
+
+    if (KnownSrc.One[SrcBits - 1])
+      Known.One.setLowBits(NumElts);
+    else if (KnownSrc.Zero[SrcBits - 1])
+      Known.Zero.setLowBits(NumElts);
+    return false;
+   }
   }
 
   return TargetLowering::SimplifyDemandedBitsForTargetNode(
@@ -39566,10 +39599,11 @@ static SDValue combineMOVMSK(SDNode *N, SelectionDAG &DAG,
                              TargetLowering::DAGCombinerInfo &DCI) {
   SDValue Src = N->getOperand(0);
   MVT SrcVT = Src.getSimpleValueType();
+  MVT VT = N->getSimpleValueType(0);
 
   // Perform constant folding.
   if (ISD::isBuildVectorOfConstantSDNodes(Src.getNode())) {
-    assert(N->getValueType(0) == MVT::i32 && "Unexpected result type");
+    assert(VT== MVT::i32 && "Unexpected result type");
     APInt Imm(32, 0);
     for (unsigned Idx = 0, e = Src.getNumOperands(); Idx < e; ++Idx) {
       SDValue In = Src.getOperand(Idx);
@@ -39577,7 +39611,7 @@ static SDValue combineMOVMSK(SDNode *N, SelectionDAG &DAG,
           cast<ConstantSDNode>(In)->getAPIntValue().isNegative())
         Imm.setBit(Idx);
     }
-    return DAG.getConstant(Imm, SDLoc(N), N->getValueType(0));
+    return DAG.getConstant(Imm, SDLoc(N), VT);
   }
 
   // Look through int->fp bitcasts that don't change the element width.
@@ -39587,11 +39621,10 @@ static SDValue combineMOVMSK(SDNode *N, SelectionDAG &DAG,
         EVT(SrcVT).changeVectorElementTypeToInteger())
     Src = Src.getOperand(0);
 
+  // Simplify the inputs.
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
-
-  // MOVMSK only uses the MSB from each vector element.
-  APInt DemandedMask(APInt::getSignMask(SrcVT.getScalarSizeInBits()));
-  if (TLI.SimplifyDemandedBits(Src, DemandedMask, DCI))
+  APInt DemandedMask(APInt::getAllOnesValue(VT.getScalarSizeInBits()));
+  if (TLI.SimplifyDemandedBits(SDValue(N, 0), DemandedMask, DCI))
     return SDValue(N, 0);
 
   // Combine (movmsk (setne (and X, (1 << C)), 0)) -> (movmsk (X << C)).
diff --git a/llvm/test/CodeGen/X86/movmsk.ll b/llvm/test/CodeGen/X86/movmsk.ll
index 623f92b4342..eebcf181196 100644
--- a/llvm/test/CodeGen/X86/movmsk.ll
+++ b/llvm/test/CodeGen/X86/movmsk.ll
@@ -134,11 +134,10 @@ define i32 @demandedbits_v16i8(<16 x i8> %x) {
   ret i32 %2
 }
 
-; TODO: Simplify demanded vector elts
+; Simplify demanded vector elts
 define i32 @demandedelts_v4f32(<4 x float> %x) {
 ; CHECK-LABEL: demandedelts_v4f32:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    shufps {{.*#+}} xmm0 = xmm0[0,0,0,0]
 ; CHECK-NEXT:    movmskps %xmm0, %eax
 ; CHECK-NEXT:    andl $1, %eax
 ; CHECK-NEXT:    retq