[PATCH] D60601: [DAGCombiner] Exploiting more about the transformation of TransformFPLoadStorePair function

Sun Apr 14 19:28:56 PDT 2019

wuzish added a comment.

In D60601#1464855 <https://reviews.llvm.org/D60601#1464855>, @efriedma wrote:

> I can't find any previous discussion of this particular check.  I agree it isn't necessary for correctness.
>
> Do you have any benchmarks showing this actually helps?  I'm a little concerned that this might not be a performance win in practice due to register pressure.

Thank you. It's actually a concern about register pressure.  And the previous code also has such risk.
I have run the spec2017 in POWER target, but not in ARM because I am trying to enable this for POWER in a follow-up patch and I don't have ARM machine to test. 
No obvious performance degression was found in POWER. And I think it's too long time ago (code of 2011) to find the discussion of this particular check.

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https://reviews.llvm.org/D60601