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

[Tobias Grosser via llvm-commits]

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