[PATCH] D63652: [InstCombine] (1 << (C - x)) -> ((1 << C) >> x) if C is bitwidth - 1

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri accepted this revision.
lebedev.ri added a comment.
This revision is now accepted and ready to land.

Please precommit those 3 extra tests first though



================
Comment at: test/Transforms/InstCombine/shl-sub.ll:56
 }
 
 ; Negative tests
----------------
missing 3 tests with undef:
```
define <3 x i64> @shl_sub_i64_vec_undef0(<3 x i64> %x) {
  %s = sub <3 x i64> <i64 63, i64 undef, i64 63>, %x
  %r = shl <3 x i64> <i64 1, i64 1, i64 1>, %s
  ret <3 x i64> %r
}

define <3 x i64> @shl_sub_i64_vec_undef1(<3 x i64> %x) {
  %s = sub <3 x i64> <i64 63, undef, i64 63>, %x
  %r = shl <3 x i64> <i64 1, i64 undef, i64 1>, %s
  ret <3 x i64> %r
}

define <3 x i64> @shl_sub_i64_vec_undef2(<3 x i64> %x) {
  %s = sub <3 x i64> <i64 63, i64 undef, i64 63>, %x
  %r = shl <3 x i64> <i64 1, i64 undef, i64 1>, %s
  ret <3 x i64> %r
}

```


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  https://reviews.llvm.org/D63652/new/

https://reviews.llvm.org/D63652