[PATCH] PR 23155 - Improvement to X86 16 bit operation promotion for better performance.

[Chandler Carruth]

In http://reviews.llvm.org/D9209#162887, @kbsmith1 wrote:

> From Chandler's comments in 22473:
>  We need to add a pass that replaces movb (and movw) with movzbl (and movzwl) when the destination is a register and the high bytes aren't used. Then we need to benchmark bzip2 to ensure that this recovers all of the performance that forcing the use of cmpl did, and probably some other sanity benchmarking. Then we can swap the cmpl formation for the movzbl formation.
>
> I am in agreement that this would be a good solution.  If you, Chandler, and Eric all like that direction, I will be willing to work on that.  I also have access to SPEC benchmarks, both 2000 and 2006 to be able to benchmark as well for bzip2 specifically since that is something the community considers important.


I would be *very* interested in this, and would love it if you could work on it. I suspect you're in a much better position to implement, document, and evaluate the results. We really need to kill the 'cmpl' hack that is currently used.


REPOSITORY
  rL LLVM

http://reviews.llvm.org/D9209

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/