[polly] r248119 - Add loop trip count based heuristic for SCoP detection

[Johannes Doerfert via llvm-commits]

Though we should aim for an optimization for such cases.

On 09/21, Tobias Grosser wrote:
> On 09/20/2015 04:56 PM, Johannes Doerfert via llvm-commits wrote:
> >Author: jdoerfert
> >Date: Sun Sep 20 09:56:54 2015
> >New Revision: 248119
> >
> >URL: http://llvm.org/viewvc/llvm-project?rev=248119&view=rev
> >Log:
> >Add loop trip count based heuristic for SCoP detection
> >
> >   As we currently do not perform any optimizations that targets (or is
> >   even aware) small trip counts we will skip them when we count the
> >   loops in a region.
> 
> Thank you, Johannes.
> 
> This commit was a small, but strict improvement in respect of compile time
> and run-time:
> 
> http://llvm.org/perf/db_default/v4/nts/42438
> 
> Performance Improvements - Compile Time
> 
> 	Δ 	Previous 	Current 	σ 	Δ (B) 	σ (B)
> SingleSource/Benchmarks/Misc/flops-3
> 	-33.33% 	0.0480 	0.0320 	0.0060 	-54.61% 0.0060
> MultiSource/Benchmarks/McCat/08-main/main
> 	-9.23% 		0.5200 	0.4720 	0.0123 	-10.45% 0.0123
> MultiSource/Benchmarks/MiBench/consumer-lame/consumer-lame
> 	-5.31% 		9.0441 	8.5641 	0.0354 	-0.25% 	0.0354
> MultiSource/Applications/JM/ldecod/ldecod
> 	-4.13% 		14.2446	13.6566	0.0400 	7.58% 	0.0400
> MultiSource/Benchmarks/mediabench/mpeg2/mpeg2dec/mpeg2decode
> 	-3.47% 		2.7640 	2.6680 	0.0241 	-3.33% 	0.0241
> MultiSource/Benchmarks/nbench/nbench
> 	-2.99% 		3.0801 	2.9881 	0.0119 	27.03% 	0.0119
> MultiSource/Applications/JM/lencod/lencod
> 	-2.06% 		31.3976	30.7495 0.0732 	13.11% 	0.0732
> 
> Performance Improvements - Execution Time
> 	Δ 	Previous 	Current 	σ 	Δ (B) 	σ (B)
> MultiSource/Benchmarks/TSVC/LoopRestructuring-flt/LoopRestructuring-flt
> 	-13.35% 	3.1762 	2.7522 	0.0024 	61.13% 	0.0024
> 
> Best,
> Tobias
> 
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-- 

Johannes Doerfert
Researcher / PhD Student

Compiler Design Lab (Prof. Hack)
Saarland University, Computer Science
Building E1.3, Room 4.31

Tel. +49 (0)681 302-57521 : doerfert at cs.uni-saarland.de
Fax. +49 (0)681 302-3065  : http://www.cdl.uni-saarland.de/people/doerfert
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