• Ross McIlroy's avatar
    [TurboFan] Add typing for the EmptyString and use this for JSToPrimitiveToString · 2c296b7e
    Ross McIlroy authored
    Add the ability for the typer to track whether a string could be the empty
    string. This is needed for typed lowering of JSStringConcat since we can't
    create cons string chain with the empty string in arbitrary positions.
    
    The ToPrimitiveToString bytecode handler is modified to collect feedback on
    whether it has ever seen the empty string, which is used by
    SpeculativeToPrimitiveToString to ensure that the output is non-empty (or
    depot) which will subsiquently be used to enable inline cons-string creation
    for the JSStringConcat operator in typed lowering in a subsiquent CL.
    
    BUG=v8:6243
    
    Change-Id: I41b99b59798993f756aada8cff90fb137d65ea52
    Reviewed-on: https://chromium-review.googlesource.com/522122
    Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
    Reviewed-by: 's avatarJaroslav Sevcik <jarin@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#45786}
    2c296b7e
js-type-hint-lowering.cc 12.2 KB