[PATCH] D66287: GlobalISel: add combiner for indexed loads and stores

[Amara Emerson via Phabricator via llvm-commits]

aemerson added a comment.

In D66287#1642767 <https://reviews.llvm.org/D66287#1642767>, @t.p.northover wrote:

> > My one concern is with adding the machine dominator analysis the the pipeline at -O0. Is there a significant compile time cost?
>
> Doesn't look like it. I did a few runs of the test-suite, and it came out at maybe 1% difference but the numbers were pretty noisy. I'd be inclined to leave it, though it would certainly be possible to only use MachineDominator at higher levels.


Is that running the entire combine or just the MDT? If the latter, it's still non-negligible, but if there are code size savings to be had then its ok for me.

> 
> 
>> It's ok if we can pay for it by reducing the amount of code to analyze but we should run the numbers to check.
> 
> I doubt this is the kind of optimization that would pay for itself in that way.




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