[PATCH] Make InstCombine aware of TargetTransformInfo when optimize extension

[Chandler Carruth]

This doesn't seem like the right approach at all.

I don't think we want to use cost heuristics to dictate the canonical form in the IR. It makes the canonicalization *much* more complex and hard to manage.

I think that NVPTX should either change the datalayout to make i64 illegal (and that seems reasonable for instcombine to respect, but that would for example mean it would be an *absolute* decision, not a cost decision) or you'll need to do a late transform to narrow the operations as much as possible.


http://reviews.llvm.org/D10750

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