[PATCH] D124369: [InstCombine] C0 >>{ashr, exact} (X - C1) --> (C0 << C1) >>{ashr} X

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

1. Please write a more general proof for these transforms. See examples in the comments here: https://github.com/llvm/llvm-project/issues/54890
2. Does the lshr transform require "exact" or not?
3. We need several tests - including "negative" tests that show that the transform does NOT occur when the pre-conditions are not met. You can use the existing tests for the 'shl' transform as a template (those are just below the tests added in this patch).
4. It would be better to create a small helper function rather than duplicate code for these transforms - can this live under `InstCombinerImpl::commonShiftTransforms()`? Would it include the existing `shl` transform too?


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