[PATCH] [SLSR] handle candidate form &B[i * S]

[Andrew Trick]

Good observation, Hal. SCEV is there for you to use, so you might as well. I agree that we don't want to reinvent the abstraction over arithmetic expressions in each pass. I will mention two issues:

(1) SCEV may end up recursively evaluating more of the expression than you need, which could be expensive. In the first patch, you had a very simple pattern match, so SCEV didn't seem worthwhile. As you try to cover more patterns, SCEV makes more sense.

(2) SCEVExpander is fraught with peril. If you can use SCEV to help discover candidates, but leave your rewriteCandidateWithBases() code as-is, then you have nothing to worry about. If you want to use SCEVExpander then you need to be very careful about the expressions you generate.


http://reviews.llvm.org/D7459

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