• Seth Brenith's avatar
    [interpreter] Short Star bytecode · cf93071c
    Seth Brenith authored
    Design doc:
    https://docs.google.com/document/d/1g_NExMT78II_KnIYNa9MvyPYIj23qAiFUEsyemY5KRk/edit
    
    This change adds 16 new interpreter opcodes, kStar0 through kStar15, so
    that we can use a single byte to represent the common operation of
    storing to a low-numbered register. This generally reduces the quantity
    of bytecode generated on web sites by 8-9%.
    
    In order to not degrade speed, a couple of other changes are required:
    
    The existing lookahead logic to check for Star after certain other
    bytecode handlers is updated to check for these new short Star codes
    instead. Furthermore, that lookahead logic is updated to contain its own
    copy of the dispatch jump rather than merging control flow with the
    lookahead-failed case, to improve branch prediction.
    
    A bunch of constants use bytecode size in bytes as a proxy for the size
    or complexity of a function, and are adjusted downward proportionally to
    the decrease in generated bytecode size.
    
    Other small drive-by fix: update generate-bytecode-expectations to emit
    \n instead of \r\n on Windows.
    
    Change-Id: I6307c2b0f5794a3a1088bb0fb94f6e1615441ed5
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2641180Reviewed-by: 's avatarRoss McIlroy <rmcilroy@chromium.org>
    Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
    Cr-Commit-Position: refs/heads/master@{#72773}
    cf93071c
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