[PATCH] D59174: [DAGCombine] Fold (x & ~y) | y patterns

Sun Mar 17 04:08:26 PDT 2019

nikic marked 2 inline comments as done.
nikic added inline comments.

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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:5429

+  // fold (or (and X, (xor Y, -1)), Y) -> (or X, Y)
+  if (N0.getOpcode() == ISD::AND && isBitwiseNot(N0.getOperand(1)) &&
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lebedev.ri wrote:
> There are 4 variations of this pattern, both `or` and `and` are commutative.
Right you are. I've added these now, which resulted in a few more changes to the variablemask tests. I was under the mistaken impression that `(and X, (xor Y, -1))` is a canonicalized and-not pattern.

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Comment at: llvm/test/CodeGen/X86/unfold-masked-merge-vector-variablemask-const.ll:344
 ; CHECK-SSE1-NEXT:    movaps %xmm1, (%rdi)
 ; CHECK-SSE1-NEXT:    retq
 ;
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Looks like this doesn't fold for the SSE1 case, because FXOR and friends are created via custom DAG combine very early on.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59174/new/

https://reviews.llvm.org/D59174