[PATCH] Optimize unrolled reductions in LoopStrengthReduce

Eric Christopher echristo at gmail.com
Sun Feb 8 09:16:35 PST 2015

FWIW I'm not such a huge fan of using register pressure heuristics in the
middle end, it has a tendency to hide code gen deficiencies or be
suboptimal in cases where we could do better if we did the optimization and
let code generation fold things together/MachineLICM/etc. I understand
where the desires come from, but if possible I like to optimize as hard as
we can in the middle end and clean it up using machine optimizations.

Yes, I know this isn't always practical, but...


On Thu Jan 22 2015 at 9:43:44 PM hfinkel at anl.gov <hfinkel at anl.gov> wrote:

> I agree, this needs a register-pressure threshold. Also, I thought that
> the loop vectorizer would also perform this transformation as part of its
> interleaved unrolling capability. Does it not? If not, perhaps it really
> belongs there (and the vectorizer already has register pressure heuristics)?
> http://reviews.llvm.org/D7128
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