[llvm] [GlobalISel] Combine G_ZEXT of undef -> 0 (PR #113764)

[Craig Topper via llvm-commits]

Thorsten =?utf-8?q?Schütt?= <schuett at gmail.com>
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In-Reply-To: <llvm.org/llvm/llvm-project/pull/113764 at github.com>


topperc wrote:

> If the match function indicates that a change is being made, but the change is never made, won't that cause the combiner to iterate repeatedly until it hits the MaxIterations limit?

As an experiment I made replaceInstWithConstant not make any change and increased the MaxIteration limit to 5. As I expected the combiner ran 5 times.

https://github.com/llvm/llvm-project/pull/113764