[X86][SSE] Add support for combining ISD::AND with shuffles.

Attempts to convert an AND with a vector of 255 or 0 values into a shuffle (blend) mask.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288333 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86ISelLowering.cpp

@@ -5558,6 +5558,25 @@ static bool getFauxShuffleMask(SDValue N, SmallVectorImpl<int> &Mask,
 
   unsigned Opcode = N.getOpcode();
   switch (Opcode) {
+  case ISD::AND: {
+    // Attempt to decode as a per-byte mask.
+    SmallBitVector UndefElts;
+    SmallVector<APInt, 32> EltBits;
+    if (!getTargetConstantBitsFromNode(N.getOperand(1), 8, UndefElts, EltBits))
+      return false;
+    for (int i = 0, e = (int)EltBits.size(); i != e; ++i) {
+      if (UndefElts[i]) {
+        Mask.push_back(SM_SentinelUndef);
+        continue;
+      }
+      uint64_t ByteBits = EltBits[i].getZExtValue();
+      if (ByteBits != 0 && ByteBits != 255)
+        return false;
+      Mask.push_back(ByteBits == 0 ? SM_SentinelZero : i);
+    }
+    Ops.push_back(N.getOperand(0));
+    return true;
+  }
   case X86ISD::VSHLI:
   case X86ISD::VSRLI: {
     uint64_t ShiftVal = N.getConstantOperandVal(1);

test/CodeGen/X86/vector-shuffle-combining-avx2.ll

@@ -72,13 +72,11 @@ define <32 x i8> @combine_pshufb_vpermps(<8 x float> %a) {
 define <32 x i8> @combine_and_pshufb(<32 x i8> %a0) {
 ; X32-LABEL: combine_and_pshufb:
 ; X32:       # BB#0:
-; X32-NEXT:    vpand {{\.LCPI.*}}, %ymm0, %ymm0
 ; X32-NEXT:    vpshufb {{.*#+}} ymm0 = ymm0[0,1],zero,zero,zero,zero,zero,zero,ymm0[8,9],zero,zero,zero,zero,zero,zero,ymm0[16,17],zero,zero,zero,zero,zero,zero,ymm0[24,25],zero,zero,zero,zero,zero,zero
 ; X32-NEXT:    retl
 ;
 ; X64-LABEL: combine_and_pshufb:
 ; X64:       # BB#0:
-; X64-NEXT:    vpand {{.*}}(%rip), %ymm0, %ymm0
 ; X64-NEXT:    vpshufb {{.*#+}} ymm0 = ymm0[0,1],zero,zero,zero,zero,zero,zero,ymm0[8,9],zero,zero,zero,zero,zero,zero,ymm0[16,17],zero,zero,zero,zero,zero,zero,ymm0[24,25],zero,zero,zero,zero,zero,zero
 ; X64-NEXT:    retq
   %1 = shufflevector <32 x i8> %a0, <32 x i8> zeroinitializer, <32 x i32> <i32 0, i32 1, i32 32, i32 32, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15, i32 16, i32 17, i32 18, i32 19, i32 20, i32 21, i32 22, i32 23, i32 24, i32 25, i32 26, i32 27, i32 28, i32 29, i32 30, i32 31>

test/CodeGen/X86/vector-shuffle-combining-ssse3.ll

@@ -277,8 +277,7 @@ define <16 x i8> @combine_pshufb_psrldq(<16 x i8> %a0) {
 define <16 x i8> @combine_and_pshufb(<16 x i8> %a0) {
 ; SSSE3-LABEL: combine_and_pshufb:
 ; SSSE3:       # BB#0:
-; SSSE3-NEXT:    pand {{.*}}(%rip), %xmm0
+; SSSE3-NEXT:    pshufb {{.*#+}} xmm0 = zero,zero,zero,zero,zero,zero,zero,zero,xmm0[8,9],zero,zero,zero,zero,zero,zero
-; SSSE3-NEXT:    pshufb {{.*#+}} xmm0 = xmm0[0,1],zero,zero,zero,zero,zero,zero,xmm0[8,9],zero,zero,zero,zero,zero,zero
 ; SSSE3-NEXT:    retq
 ;
 ; SSE41-LABEL: combine_and_pshufb: