[all-commits] [llvm/llvm-project] 5bc0bd: [AArch64][GlobalISel] Fold G_XOR x, -1 into G_SELE...

[Jessica Paquette via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 5bc0bd05e6a8d788e08cdf3d154f3a33202aee53
      https://github.com/llvm/llvm-project/commit/5bc0bd05e6a8d788e08cdf3d154f3a33202aee53
  Author: Jessica Paquette <jpaquette at apple.com>
  Date:   2020-11-16 (Mon, 16 Nov 2020)

  Changed paths:
    M llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
    M llvm/test/CodeGen/AArch64/GlobalISel/select-select.mir

  Log Message:
  -----------
  [AArch64][GlobalISel] Fold G_XOR x, -1 into G_SELECT and select CSINV

When we see

```
xor = G_XOR xor_lhs, -1
select = G_SELECT cc, tval, xor
```

Fold this into

```
select = CSINV tval, xor_lhs, cc
```

Update select-select.mir to reflect the changes.

For now, only handle the case where the G_XOR is the false-value for the
G_SELECT. It may make more sense to handle the true-value case in post-legalizer
lowering.

Differential Revision: https://reviews.llvm.org/D90774