[PATCH] D46031: [DAGCombiner] DON'T unfold scalar masked merge if 'B' is constant

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: spatel, craig.topper, RKSimon.
Herald added a reviewer: javed.absar.

Discovered accidentally when working on the vector part, because the `@test_andnotps`/`@test_andnotpd`
in `test/CodeGen/X86/*-schedule.ll` broke - they were no longer lowered to `andnps`/`andnpd`.

Given canonical pattern of:

  |        A  |  |B|
  ((x ^ y) & m) ^ y
   |  D  |

We don't want to handle `xor`'s with second operand being constant (especially `-1`).

I *think* this is how we want to handle it?


Repository:
  rL LLVM

https://reviews.llvm.org/D46031

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/AArch64/unfold-masked-merge-scalar-variablemask.ll
  test/CodeGen/X86/unfold-masked-merge-scalar-variablemask.ll

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