[PATCH] D64557: Add llvm.loop.licm.disable metadata

[Hal Finkel via Phabricator via llvm-commits]

hfinkel added a comment.

In D64557#1580627 <https://reviews.llvm.org/D64557#1580627>, @timcorringham wrote:

> Unfortunately I don't believe I have an example that is suitable for publishing. The problem is basically that the code motion is generally a good thing, but it can increase live ranges significantly pushing register pressure up such that performance is degraded, but that impact isn't apparent at the point at which the transformation is performed. Disabling the pass for certain loops is a low-impact pragmatic (but not ideal) solution.


Is this a rematerialization problem? We do hoist things sometimes which turn into multiple instructions and then we can't rematerialize during RA.


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https://reviews.llvm.org/D64557