[PATCH] D15573: [X86] Add option for enabling LEA optimization pass

[Quentin Colombet via llvm-commits]

> On Dec 16, 2015, at 10:39 AM, Daniel Berlin <dberlin at dberlin.org> wrote:
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> dberlin added a comment.
> 
> In http://reviews.llvm.org/D15573#312043, @aturetsk wrote:
> 
>> I'm going to investigate the compile time issue and try to find ways to improve pass's speed.
>> In the worst case we can just skip LEA optimization for big basic blocks, that should keep compile time from blowing up.
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> 
> I would try the two things i suggested in the bug.  They solve the main algorithmic complexity problems with this pass.  I hacked up a patch to do them, and it completely solved the compile time issue, and i didn't see any regressions.
> 
> IMHO, We generally should only be inserting big-hammer compile time controls and random "stop after 10" style things if we can't reasonably make the algorithmic complexity better.
> (among other reasons, we end up with a compiler that has sudden changes in optimization behavior depending on if your block has 999 instructions or 1000 instructions)

+1

Q.

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> 
> http://reviews.llvm.org/D15573
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>