[PATCH] D21560: Relax the clearance calculating for breaking partial register dependency.

[Sanjay Patel via llvm-commits]

spatel accepted this revision.
spatel added a comment.
This revision is now accepted and ready to land.

In http://reviews.llvm.org/D21560#468552, @danielcdh wrote:

> I just tested the perf impact of this patch for SPECCPU INT2006 benchmarks (perf test were done on sandybridge):
>
> 400.perlbench	2.21%
>  401.bzip2	-0.46%
>  403.gcc	1.59%
>  429.mcf	1.79%
>  445.gobmk	1.52%
>  456.hmmer	1.63%
>  458.sjeng	5.62%
>  462.libquantum	1.54%
>  464.h264ref	-1.28%
>  471.omnetpp	0.00%
>  473.astar	2.35%
>  483.xalancbmk	-0.27%
>  overall	1.29%


That is a surprisingly large gain. This raises the question: if 64 is good, is 128 even better?

> About the -Oz issue, I agree that there should be no xor inserted at -Oz. But that's a different issue and should be fixed in a separate patch.


Agreed. Please let me know if you plan to follow-up on that part.

I have no further comments on this patch, so LGTM.


http://reviews.llvm.org/D21560