[Webkit-unassigned] [Bug 144136] New: Better optimize 'if' with ternaries conditional tests.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=144136

            Bug ID: 144136
           Summary: Better optimize 'if' with ternaries conditional tests.
    Classification: Unclassified
           Product: WebKit
           Version: 528+ (Nightly build)
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: dtc-llvm at scieneer.com

For asm.js code it is very important to optimize an 'if' statement with a '?' ternaries conditional. Asm.js does not support && and || and Emscripten has for some time optimized these patterns to "a?b:0" for "a&&b" and "a?1:b" for "a||b". JSC FTL does not seem to optimize 'if (a?b:0)' well and produces much faster code for 'if(a && b)' or 'if (a) if(b)' - it almost doubles the run time for the zlib benchmark. This might not be noticed in old asm.js code which did not use these patterns, but the Emscripten 'simplifyIfs' optimization has been in use for some time now. There might be some other patterns that could be optimized too. The Odin support might be a good reference, see https://bugzilla.mozilla.org/show_bug.cgi?id=919052

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