[Webkit-unassigned] [Bug 101782] New: 37% sunspider regression

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=101782

           Summary: 37% sunspider regression
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Tools / Tests
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: ojan at chromium.org
                CC: abarth at webkit.org, dglazkov at chromium.org,
                    morrita at google.com, shinyak at chromium.org


It shows in some of the other sunspider tests as well, but here are the most clear graphs.

http://build.chromium.org/f/chromium/perf/chromium-rel-win7-webkit/sunspider/report.html?rev=166898&graph=math-spectral-norm&trace=t&history=150

http://build.chromium.org/f/chromium/perf/chromium-rel-win7-webkit/sunspider/report.html?rev=166898&graph=access-fannkuch&trace=t&history=150

http://build.chromium.org/f/chromium/perf/chromium-rel-win7-webkit/sunspider/report.html?rev=166898&graph=bitops-3bit-bits-in-byte&trace=t&history=150

It's clearly not a chromium side change. Chromium regression range: http://build.chromium.org/f/chromium/perf/dashboard/ui/changelog.html?url=/trunk/src&mode=html&range=166683:166688

WebKit regression range: http://trac.webkit.org/log/?verbose=on&rev=133904&stop_rev=133902

Looks pretty clearly to be http://trac.webkit.org/changeset/133904/, since we got the equivalent performance gain when http://trac.webkit.org/changeset/133429/ was committed.

It would be good to understand what http://trac.webkit.org/changeset/133429/ does better so we can understand:
a) Why it makes sunspider so much faster.
b) Why it made the other tests slower and use more memory.

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