JavaScript benchmark results of Firefox PGO build made with VC2013 are often slower than those of non-PGO build - by tete009

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  Not Reproducible<br /><br />
		The product team could not reproduce this item with the description and steps provided.<br /><br />
		A more detailed explanation for the resolution of this particular item may have been provided in the comments section.

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ID 825015 Comments
Status Closed Workarounds
Type Bug Repros 0
Opened 2/27/2014 8:55:21 AM
Access Restriction Public


I built Firefox 30.0a1 PGO/non-PGO unofficial builds from a same source code, using VS2013 Update 1.
I got the results that some JavaScript benchmark results of the PGO build are slower than those of the non-PGO build.


SunSpider 1.0.2 (repeatCount=30)
-O2: 167.4ms (+/- 1.1%)
-O2 PGO: 177.6ms (+/- 1.0%)

kraken-1.1 (repeatCount=30)
-O2: 1291.7ms (+/- 1.3%)
-O2 PGO: 1341.8ms (+/- 1.7%)

I had built unofficial Firefox PGO builds using VC2005 for years. In many cases, PGO builds made with VC2005 had shown better benchmark results than non-PGO ones.

Messages at when PGO of VC2013 was applied to mozjs.dll:

548 of 43005 (  1.27%) profiled functions will be compiled for speed, and the rest of the functions will be compiled for size
56726 of 352725 inline instances were from dead/cold paths 
41822 of 43005 functions (97.2%) were optimized using profile data, and the rest of the functions were optimized without using profile data
11168873681 of 11168873681 instructions (100.0%) were optimized using profile data, and the rest of the instructions were optimized without using profile data
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Posted by Microsoft on 5/29/2014 at 1:03 AM
Thanks for your feedback. I'm glad to hear that your issue has been resolved. Based on your description, I will close this issue. Should you find any bugs in the future, please feel free to let us know.
Posted by tete009 on 5/2/2014 at 9:14 PM
I think PGO has been improved between VS2013 Update 1 and Update 2 RC. Thank you very much for fixing the problem.

JavaScript benchmark results of my unofficial builds of Firefox 29.0 (built with VS2013 Update 2 RC):

SunSpider 1.0.2 (repeatCount=30)
-O2: 164.2ms +/- 1.1%
-O2 -GL: 155.1ms +/- 0.9%
-O2 PGO: 144.7ms +/- 0.6%

kraken-1.1 (repeatCount=30)
-O2: 1288.7ms +/- 1.7%
-O2 -GL: 1267.9ms +/- 1.3%
-O2 PGO: 1228.3ms +/- 1.1%
Posted by Microsoft on 2/28/2014 at 1:39 AM
Thank you for submitting feedback on Visual Studio and .NET Framework. Your issue has been routed to the appropriate VS development team for review. We will contact you if we require any additional information. If you require immediate assistance with this issue, please contact product support at
Posted by Microsoft on 2/27/2014 at 9:51 AM
Thank you for your feedback, we are currently reviewing the issue you have submitted. If this issue is urgent, please contact support directly(