[PATCH] D36395: [InstCombine] narrow rotate left/right patterns to eliminate zext/trunc (PR34046)

[Sanjay Patel via Phabricator via llvm-commits]

spatel updated this revision to Diff 110088.
spatel added a comment.

Patch updated:

1. Add an assert for the shouldChangeType() guard that's in the caller function.
2. Replace the explicit match for zext of the shift value with a call to MaskedValueIsZero().
3. Remove the MaskedValueIsZero() check for the shift amount and generate our own masks to make the transform safe:

http://rise4fun.com/Alive/Qzm

4. Add test to exercise #2 and #3.


https://reviews.llvm.org/D36395

Files:
  lib/Transforms/InstCombine/InstCombineCasts.cpp
  lib/Transforms/InstCombine/InstCombineInternal.h
  test/Transforms/InstCombine/rotate.ll

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