[PATCH][Review Requested][Compilation Time] Calculate hash value and equality comparison within SCEV node itself

[Murali, Sriram]

Hi Duncan,
I reran the tests several times to obtain the standard deviation, and found that there is little to no deviation in the runs

without patch	with patch	improvement
avg	stdev	avg	stdev	
14.73	0.05	14.31	0.14	2.89
14.59	0.29	13.99	0.09	4.14
15.92	0.18	15.36	0.17	3.48
18.75	0.19	18.32	0.29	2.33
15.40	0.16	15.08	0.11	2.07
17.22	0.13	16.98	0.26	1.40
18.46	0.06	18.32	0.53	0.79
17.07	0.06	16.76	0.29	1.82
13.55	0.12	12.94	0.23	4.46
17.53	0.18	17.63	0.27	-0.61
16.37	0.09	16.27	0.36	0.60
12.09	0.02	11.85	0.22	2.05
8.36	0.08	8.14	0.12	2.54
12.82	0.04	12.76	0.16	0.52
28.79	0.27	27.49	0.42	4.52
4.89	0.04	4.89	0.18	-0.02
22.04	0.11	21.52	0.55	2.38
9.18	0.12	8.81	0.17	4.06
7.78	0.12	7.69	0.23	1.08

Thanks
Ram

-----Original Message-----
From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-bounces at cs.uiuc.edu] On Behalf Of Duncan Sands
Sent: Tuesday, February 05, 2013 10:39 AM
To: llvm-commits at cs.uiuc.edu
Subject: Re: [PATCH][Review Requested][Compilation Time] Calculate hash value and equality comparison within SCEV node itself

Hi Sriram,

On 04/02/13 20:39, Murali, Sriram wrote:
> SCEV is currently implemented as a FoldingSetNode to calculate the 
> hashing value and for equality comparison. This causes some 
> performance loss. This patch aims at improving the compilation time 
> performance by implementing the hashing and equality comparison within 
> SCEV class instead of inheriting FoldingSetNode. The compilation performance gain for this particular refactoring is around 2%.

sorry to be a pain, but such numbers are meaningless without an estimate of the variance.  In short, are the apparent differences statistically significant, or might they just be random noise?

Ciao, Duncan.

>
> This patch is part of a series of compile time improvements. Although 
> these were originally produced by our colleague Wan Xiaofei, our team 
> consisting of tyler.nowicki at intel.com 
> <mailto:tyler.nowicki at intel.com>; preston.gurd at intel.com 
> <mailto:preston.gurd at intel.com>; and sriram.murali at intel.com <mailto:sriram.murali at intel.com>, are assuming all responsibility for this work.
>
> Please Review
>
> Thanks
>
> Sriram Murali
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