[PATCH] D13417: [MachineCombiner] make slack optional in critical path cost calculation (PR25016)

[Gerolf Hoflehner via llvm-commits]

We should avoid scenarios where two types of machine combines suddenly would require a different heuristic within the same block, eg assume a madd combine and a reassoc in the same block. Also, on a minor note I don’t think I truly understand your underpinning performance issue yet.

Gerolf

> On Oct 5, 2015, at 2:28 PM, Sanjay Patel <spatel at rotateright.com> wrote:
> 
> spatel retitled this revision from "[MachineCombiner] remove "slack"  from critical path cost calculation (PR25016)" to "[MachineCombiner] make slack optional in critical path cost calculation (PR25016)".
> spatel updated the summary for this revision.
> spatel updated this revision to Diff 36552.
> spatel added a comment.
> Herald added a subscriber: aemerson.
> 
> Patch updated:
> Make slack an optional part of the critical path calculation. Slack is still used with the AArch64 MULADD patterns, but not with the reassociation patterns where it may cause harm.
> 
> 
> http://reviews.llvm.org/D13417
> 
> Files:
>  include/llvm/CodeGen/MachineCombinerPattern.h
>  lib/CodeGen/MachineCombiner.cpp
>  test/CodeGen/X86/machine-combiner.ll
> 
> <D13417.36552.patch>