This commit contains a few changes that had to go in together.

1. Simplify xor/and/or (bitcast(A), bitcast(B)) -> bitcast(op (A,B))
   (and also scalar_to_vector).

2. Xor/and/or are indifferent to the swizzle operation (shuffle of one src).
   Simplify xor/and/or (shuff(A), shuff(B)) -> shuff(op (A, B))

3. Optimize swizzles of shuffles:  shuff(shuff(x, y), undef) -> shuff(x, y).

4. Fix an X86ISelLowering optimization which was very bitcast-sensitive.

Code which was previously compiled to this:

movd    (%rsi), %xmm0
movdqa  .LCPI0_0(%rip), %xmm2
pshufb  %xmm2, %xmm0
movd    (%rdi), %xmm1
pshufb  %xmm2, %xmm1
pxor    %xmm0, %xmm1
pshufb  .LCPI0_1(%rip), %xmm1
movd    %xmm1, (%rdi)
ret

Now compiles to this:

movl    (%rsi), %eax
xorl    %eax, (%rdi)
ret

llvm-svn: 153848

1 files changed, 7 insertions, 8 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 88f38298db0..69a60361314 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -14000,13 +14000,14 @@ static SDValue PerformOrCombine(SDNode *N, SelectionDAG &DAG,
         return SDValue();
 
       // Validate that X, Y, and Mask are BIT_CONVERTS, and see through them.
-      if (Mask.getOpcode() != ISD::BITCAST ||
-          X.getOpcode() != ISD::BITCAST ||
-          Y.getOpcode() != ISD::BITCAST)
-        return SDValue();
-
       // Look through mask bitcast.
-      Mask = Mask.getOperand(0);
+      if (Mask.getOpcode() == ISD::BITCAST)
+        Mask = Mask.getOperand(0);
+      if (X.getOpcode() == ISD::BITCAST)
+        X = X.getOperand(0);
+      if (Y.getOpcode() == ISD::BITCAST)
+        Y = Y.getOperand(0);
+
       EVT MaskVT = Mask.getValueType();
 
       // Validate that the Mask operand is a vector sra node.
@@ -14027,8 +14028,6 @@ static SDValue PerformOrCombine(SDNode *N, SelectionDAG &DAG,
       // Now we know we at least have a plendvb with the mask val.  See if
       // we can form a psignb/w/d.
       // psign = x.type == y.type == mask.type && y = sub(0, x);
-      X = X.getOperand(0);
-      Y = Y.getOperand(0);
       if (Y.getOpcode() == ISD::SUB && Y.getOperand(1) == X &&
           ISD::isBuildVectorAllZeros(Y.getOperand(0).getNode()) &&
           X.getValueType() == MaskVT && Y.getValueType() == MaskVT) {