[Patch] Tuning the strategy in SLP vectoriezer

[Hal Finkel]

----- Yi Jiang <yjiang at apple.com> wrote:
> Hi, 
> 
> In this patch we are trying to do two things:
> 1) If the width of vectorization list candidate is bigger than vector reg width, we will break it down to fit the vector reg.
> 2) We do not vectorize the width which is not power of two. 

Can you please explain the motivation for the power-of-two restriction? Vectorizing into 3xsomething is an important use case. If you must disable it because of poor codegen on some platforms, please provide a TTI function so that it can be enabled on targets that do a better job.

Thanks,
Hal



> 
> Here is the performance result of the change and we use ref input. Any comments and suggestions are appreciated. 
> 
> 
> 
> Performance Regressions - Execution Time	Δ	Previous	Current	σ	Δ (B)	σ (B)
> External/SPEC/CINT95/134_perl/134_perl	2.76%	2.9533	3.0348	0.0024	0.00%	0.0024
> 
> 
> Performance Improvements - Execution Time	Δ	Previous	Current	σ	Δ (B)	σ (B)
> External/SPEC/CFP2000/177_mesa/177_mesa	-6.97%	21.1910	19.7130	0.0223	0.00%	0.0223
> SingleSource/Benchmarks/BenchmarkGame/partialsums	-5.19%	0.2969	0.2815	-	0.00%	-
> External/SPEC/CFP2000/188_ammp/188_ammp	-1.54%	88.2623	86.9050	0.0823	0.00%	0.0823
> 
> 
> 
> 
> > 
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory