• Clemens Backes's avatar
    [wasm] Clean up spec'ed max memory vs dynamic max · 2d04a627
    Clemens Backes authored
    There are two different limits for the maximum memory size in
    WebAssembly:
    1) A 4GB limit which is the same on all platforms, and is observable for
    JS programs. It is used to limit the allowed declared maximum size of a
    wasm memory.
    2) A potentially lower limit (2GB on 32-bit systems, 4GB otherwise)
    which can be further limited using a command-line flag. This limit is
    used whenever actually allocating or growing a wasm memory. This limit
    is not directly observable, but we make sure that no wasm memory will
    ever be bigger than this limit.
    
    The second limit is the one we should check against when allocating or
    growing memory, while the first limit should be used when validating
    a module (or the parameters for WebAssembly.Memory). The compiler can
    rely on no memory being bigger than the second limit, which again is
    never bigger than the first limit.
    
    This CL adds some more documentation to the two limits, and cleans up
    all usages.
    This also makes {kPlatformMaxPages} and {kMaxMemoryPagesAtRuntime}
    obsolete.
    
    R=jkummerow@chromium.org
    
    Bug: chromium:1207263
    Change-Id: I43541aafd3f497d1c368bd9400e9bc667bdfd3d9
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2910787
    Commit-Queue: Clemens Backes <clemensb@chromium.org>
    Reviewed-by: 's avatarJakob Kummerow <jkummerow@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#74742}
    2d04a627
wasm-js.cc 91.3 KB