[X86] Fold not(pcmpeq(and(X,CstPow2),0)) -> pcmpeq(and(X,CstPow2),CstPow2)

Fixes #78888

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -49328,6 +49328,26 @@ static SDValue combineOrXorWithSETCC(SDNode *N, SDValue N0, SDValue N1,
     }
   }
 
+  // not(pcmpeq(and(X,CstPow2),0)) -> pcmpeq(and(X,CstPow2),CstPow2)
+  if (N->getOpcode() == ISD::XOR && N0.getOpcode() == X86ISD::PCMPEQ &&
+      N0.getOperand(0).getOpcode() == ISD::AND &&
+      ISD::isBuildVectorAllOnes(N1.getNode())) {
+    MVT VT = N->getSimpleValueType(0);
+    APInt UndefElts;
+    SmallVector<APInt> EltBits;
+    if (getTargetConstantBitsFromNode(N0.getOperand(0).getOperand(1),
+                                      VT.getScalarSizeInBits(), UndefElts,
+                                      EltBits)) {
+      bool IsPow2OrUndef = true;
+      for (unsigned I = 0, E = EltBits.size(); I != E; ++I)
+        IsPow2OrUndef &= UndefElts[I] || EltBits[I].isPowerOf2();
+
+      if (IsPow2OrUndef)
+        return DAG.getNode(X86ISD::PCMPEQ, SDLoc(N), VT, N0.getOperand(0),
+                           N0.getOperand(0).getOperand(1));
+    }
+  }
+
   return SDValue();
 }
 

llvm/test/CodeGen/X86/icmp-pow2-mask.ll

@@ -11,35 +11,29 @@ define <8 x i16> @pow2_mask_v16i8(i8 zeroext %0) {
 ; SSE2-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
 ; SSE2-NEXT:    pshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
 ; SSE2-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
-; SSE2-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
-; SSE2-NEXT:    pxor %xmm1, %xmm1
-; SSE2-NEXT:    pcmpeqb %xmm0, %xmm1
-; SSE2-NEXT:    pcmpeqd %xmm0, %xmm0
-; SSE2-NEXT:    pxor %xmm1, %xmm0
+; SSE2-NEXT:    movdqa {{.*#+}} xmm1 = [128,128,64,64,32,32,16,16,8,8,4,4,2,2,1,1]
+; SSE2-NEXT:    pand %xmm1, %xmm0
+; SSE2-NEXT:    pcmpeqb %xmm1, %xmm0
 ; SSE2-NEXT:    retq
 ;
 ; SSE41-LABEL: pow2_mask_v16i8:
 ; SSE41:       # %bb.0:
 ; SSE41-NEXT:    movd %edi, %xmm0
 ; SSE41-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
 ; SSE41-NEXT:    pshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; SSE41-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
-; SSE41-NEXT:    pxor %xmm1, %xmm1
-; SSE41-NEXT:    pcmpeqb %xmm0, %xmm1
-; SSE41-NEXT:    pcmpeqd %xmm0, %xmm0
-; SSE41-NEXT:    pxor %xmm1, %xmm0
+; SSE41-NEXT:    movdqa {{.*#+}} xmm1 = [128,64,32,16,8,4,2,1,u,u,u,u,u,u,u,u]
+; SSE41-NEXT:    pand %xmm1, %xmm0
+; SSE41-NEXT:    pcmpeqb %xmm1, %xmm0
 ; SSE41-NEXT:    pmovsxbw %xmm0, %xmm0
 ; SSE41-NEXT:    retq
 ;
 ; AVX2-LABEL: pow2_mask_v16i8:
 ; AVX2:       # %bb.0:
 ; AVX2-NEXT:    vmovd %edi, %xmm0
 ; AVX2-NEXT:    vpbroadcastb %xmm0, %xmm0
-; AVX2-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm0
-; AVX2-NEXT:    vpxor %xmm1, %xmm1, %xmm1
+; AVX2-NEXT:    vpbroadcastq {{.*#+}} xmm1 = [128,64,32,16,8,4,2,1,128,64,32,16,8,4,2,1]
+; AVX2-NEXT:    vpand %xmm1, %xmm0, %xmm0
 ; AVX2-NEXT:    vpcmpeqb %xmm1, %xmm0, %xmm0
-; AVX2-NEXT:    vpcmpeqd %xmm1, %xmm1, %xmm1
-; AVX2-NEXT:    vpxor %xmm1, %xmm0, %xmm0
 ; AVX2-NEXT:    vpmovsxbw %xmm0, %xmm0
 ; AVX2-NEXT:    retq
 ;
@@ -103,33 +97,28 @@ define i64 @pow2_mask_v8i8(i8 zeroext %0) {
 ; SSE-NEXT:    movd %edi, %xmm0
 ; SSE-NEXT:    punpcklbw {{.*#+}} xmm0 = xmm0[0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7]
 ; SSE-NEXT:    pshuflw {{.*#+}} xmm0 = xmm0[0,0,0,0,4,5,6,7]
-; SSE-NEXT:    pand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0
-; SSE-NEXT:    pxor %xmm1, %xmm1
-; SSE-NEXT:    pcmpeqb %xmm0, %xmm1
-; SSE-NEXT:    pcmpeqd %xmm0, %xmm0
-; SSE-NEXT:    pxor %xmm1, %xmm0
+; SSE-NEXT:    movdqa {{.*#+}} xmm1 = [128,64,32,16,8,4,2,1,u,u,u,u,u,u,u,u]
+; SSE-NEXT:    pand %xmm1, %xmm0
+; SSE-NEXT:    pcmpeqb %xmm1, %xmm0
 ; SSE-NEXT:    movq %xmm0, %rax
 ; SSE-NEXT:    retq
 ;
 ; AVX2-LABEL: pow2_mask_v8i8:
 ; AVX2:       # %bb.0:
 ; AVX2-NEXT:    vmovd %edi, %xmm0
 ; AVX2-NEXT:    vpbroadcastb %xmm0, %xmm0
-; AVX2-NEXT:    vpand {{\.?LCPI[0-9]+_[0-9]+}}(%rip), %xmm0, %xmm0
-; AVX2-NEXT:    vpxor %xmm1, %xmm1, %xmm1
+; AVX2-NEXT:    vpbroadcastq {{.*#+}} xmm1 = [128,64,32,16,8,4,2,1,128,64,32,16,8,4,2,1]
+; AVX2-NEXT:    vpand %xmm1, %xmm0, %xmm0
 ; AVX2-NEXT:    vpcmpeqb %xmm1, %xmm0, %xmm0
-; AVX2-NEXT:    vpcmpeqd %xmm1, %xmm1, %xmm1
-; AVX2-NEXT:    vpxor %xmm1, %xmm0, %xmm0
 ; AVX2-NEXT:    vmovq %xmm0, %rax
 ; AVX2-NEXT:    retq
 ;
 ; AVX512-LABEL: pow2_mask_v8i8:
 ; AVX512:       # %bb.0:
 ; AVX512-NEXT:    vpbroadcastb %edi, %xmm0
-; AVX512-NEXT:    vpandq {{\.?LCPI[0-9]+_[0-9]+}}(%rip){1to2}, %xmm0, %xmm0
-; AVX512-NEXT:    vpxor %xmm1, %xmm1, %xmm1
+; AVX512-NEXT:    vpbroadcastq {{.*#+}} xmm1 = [128,64,32,16,8,4,2,1,128,64,32,16,8,4,2,1]
+; AVX512-NEXT:    vpand %xmm1, %xmm0, %xmm0
 ; AVX512-NEXT:    vpcmpeqb %xmm1, %xmm0, %xmm0
-; AVX512-NEXT:    vpternlogq $15, %xmm0, %xmm0, %xmm0
 ; AVX512-NEXT:    vmovq %xmm0, %rax
 ; AVX512-NEXT:    retq
   %vec = insertelement <1 x i8> poison, i8 %0, i64 0