[PATCH] D121381: [MemorySSA] Support lazy use optimization

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

In D121381#3410466 <https://reviews.llvm.org/D121381#3410466>, @reames wrote:

> I noticed by accident that MemCpyOpt does not call ensureOptimizedUses, and thus changes behavior after this change.  Not sure if that's good or bad, but it doesn't seem to have been explicitly noted in the review.  For call slot optimization, we do perform a lot of clobber walks from loads.

I'm surprised that this would cause a change in behavior. MemCpyOpt always does clobber walks (without any limit that falls back to getDefiningAccess), so it really shouldn't care whether uses are optimized or not. Possibly our optimization cutoffs work slightly different between the eager use optimization and the clobber walk, and that can cause differences?


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