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Commit 3952c905 authored by Sanjay Patel's avatar Sanjay Patel
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[InstCombine] fold icmp equality with udiv and large constant

With large compare constant:
(X u/ Y) == C --> (X == C) && (Y == 1)
(X u/ Y) != C --> (X != C) || (Y != 1)

https://alive2.llvm.org/ce/z/EhKwh6

There are various potential missing icmp (div) transforms shown here:
https://github.com/llvm/llvm-project/issues/55695

This is a generalization for part of the udiv + equality.
I didn't check in detail, but some of those may only make sense as
codegen transforms.

This results in one extra instruction in IR, but it is better for
analysis, and looks much better in codegen on all targets that I tried.

Differential Revision: https://reviews.llvm.org/D126410
parent ea6171c1
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