Index: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
@@ -28231,7 +28231,8 @@
 
 /// If a vector select has an operand that is -1 or 0, simplify the select to a
 /// bitwise logic operation.
-static SDValue combineVSelectWithAllOnesOrZeros(SDNode *N, SelectionDAG &DAG) {
+static SDValue combineVSelectWithAllOnesOrZeros(SDNode *N, SelectionDAG &DAG,
+                                                const X86Subtarget &Subtarget) {
   SDValue Cond = N->getOperand(0);
   SDValue LHS = N->getOperand(1);
   SDValue RHS = N->getOperand(2);
@@ -28243,6 +28244,16 @@
   if (N->getOpcode() != ISD::VSELECT)
     return SDValue();
 
+  bool FValIsAllZeros = ISD::isBuildVectorAllZeros(LHS.getNode());
+  // Check if the first operand is all zeros.This situation only 
+  // applies to avx512.
+  if (FValIsAllZeros  && Subtarget.hasAVX512() && Cond.hasOneUse()) {
+      //Invert the cond to not(cond) : xor(op,allones)=not(op)
+      SDValue CondNew = DAG.getNode(ISD::XOR, DL, Cond.getValueType(), Cond,
+        DAG.getConstant(1, DL, Cond.getValueType()));
+      //Vselect cond, op1, op2 = Vselect not(cond), op2, op1
+      return DAG.getNode(ISD::VSELECT, DL, VT, CondNew, RHS, LHS);
+  }
   assert(CondVT.isVector() && "Vector select expects a vector selector!");
 
   // To use the condition operand as a bitwise mask, it must have elements that
@@ -28254,7 +28265,7 @@
     return SDValue();
 
   bool TValIsAllOnes = ISD::isBuildVectorAllOnes(LHS.getNode());
-  bool FValIsAllZeros = ISD::isBuildVectorAllZeros(RHS.getNode());
+  FValIsAllZeros = ISD::isBuildVectorAllZeros(RHS.getNode());
 
   // Try to invert the condition if true value is not all 1s and false value is
   // not all 0s.
@@ -28736,7 +28747,7 @@
     }
   }
 
-  if (SDValue V = combineVSelectWithAllOnesOrZeros(N, DAG))
+  if (SDValue V = combineVSelectWithAllOnesOrZeros(N, DAG, Subtarget))
     return V;
 
   // If this is a *dynamic* select (non-constant condition) and we can match
Index: llvm/trunk/test/CodeGen/X86/avx512-vec-cmp.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/avx512-vec-cmp.ll
+++ llvm/trunk/test/CodeGen/X86/avx512-vec-cmp.ll
@@ -658,10 +658,9 @@
 define <16 x i32> @test14(<16 x i32>%a, <16 x i32>%b) {
 ; CHECK-LABEL: test14:
 ; CHECK:       ## BB#0:
-; CHECK-NEXT:    vpsubd %zmm1, %zmm0, %zmm1
-; CHECK-NEXT:    vpcmpled %zmm0, %zmm1, %k0
-; CHECK-NEXT:    knotw %k0, %k1
-; CHECK-NEXT:    vmovdqa32 %zmm1, %zmm0 {%k1} {z}
+; CHECK-NEXT:    vpsubd	%zmm1, %zmm0, %zmm2
+; CHECK-NEXT:    vpcmpgtd %zmm0, %zmm2, %k1
+; CHECK-NEXT:    vpsubd	%zmm1, %zmm0, %zmm0 {%k1} {z}
 ; CHECK-NEXT:    retq
   %sub_r = sub <16 x i32> %a, %b
   %cmp.i2.i = icmp sgt <16 x i32> %sub_r, %a
@@ -674,10 +673,9 @@
 define <8 x i64> @test15(<8 x i64>%a, <8 x i64>%b) {
 ; CHECK-LABEL: test15:
 ; CHECK:       ## BB#0:
-; CHECK-NEXT:    vpsubq %zmm1, %zmm0, %zmm1
-; CHECK-NEXT:    vpcmpleq %zmm0, %zmm1, %k0
-; CHECK-NEXT:    knotw %k0, %k1
-; CHECK-NEXT:    vmovdqa64 %zmm1, %zmm0 {%k1} {z}
+; CHECK-NEXT:    vpsubq	%zmm1, %zmm0, %zmm2
+; CHECK-NEXT:    vpcmpgtq %zmm0, %zmm2, %k1
+; CHECK-NEXT:    vpsubq	%zmm1, %zmm0, %zmm0 {%k1} {z}
 ; CHECK-NEXT:    retq
   %sub_r = sub <8 x i64> %a, %b
   %cmp.i2.i = icmp sgt <8 x i64> %sub_r, %a