[PATCH] D35933: Eliminate TargetTransformInfo::isFoldableMemAccess()

Ulrich Weigand via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Fri Jul 28 04:46:42 PDT 2017

uweigand added a comment.

In https://reviews.llvm.org/D35933#823813, @jonpa wrote:

> > I'm not sure about the common code changes -- what does simply calling isLegalAddressingMode instead of isFoldableMemAccessOffset do to targets that have not yet added support to do instruction-specific checks to the former?  I'd assume you'd see performance regressions there.
> > 
> > Maybe this transition should be done on a target-by-target basis.
> SystemZ was the only user of isFoldableMemAccessOffset() except for any out-of-tree targets.

Well, even if they had no separate implementation, they would fall back to the default one (returning always true).   Now the code will do a call to isLegalAddressingMode instead.  Is is clear that this will either be no change (i.e. also return always true), or else an lead to an actual improvement, on all other targets?

I'm just wondering whether this could expose a performance regression on some other target ...


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