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

[Daniel Berlin via llvm-commits]

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.


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)


http://reviews.llvm.org/D15573