[Webkit-unassigned] [Bug 19508] New: Rearrange opcode bodies in VM/Machine.cpp for optimal instruction cache performance

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=19508

           Summary: Rearrange opcode bodies in VM/Machine.cpp for optimal
                    instruction cache performance
           Product: WebKit
           Version: 526+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: cwzwarich at uwaterloo.ca
                CC: mjs at apple.com, ggaren at apple.com, oliver at apple.com


There is some anecdotal evidence to suggest that the order of the opcode bodies
affects performance, especially when we add new opcodes. Given that we will be
spending a lot of effort on fusing opcodes together in the coming weeks, we
should investigate this further. In particular, we should see if reordering the
opcode bodies can increase instruction cache coherency. There are algorithms
for reordering of basic blocks based on profiling information, so we might be
able to use some of the recent instrumentation and one of these algorithms to
suggest a good placement. However, our situation is a bit different, so I don't
know how it will work out.


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