• Alessandro Pignotti's avatar
    [wasm] Avoid SSA environment reload after calls when possible · a537cb6a
    Alessandro Pignotti authored
    This patch takes advantage of memory information from the module
    to avoid unnecessary reloads of the SSA environment after a Wasm call.
    
    As far as I can sse, the SSA envinronment consists of the mem_start
    and mem_size values. Both these values cannot ever change if:
    
    	initial_mem_size == max_mem_size.
    
    Although this should be obviously true for memories defined in the
    module itself, some explanation may be necessary for imported memories.
    
    During module instantiation, the imported memory is checked as part of
    InstanceBuilder::ProcessImportedMemory. The following properties are verified:
    
    1) The current size of the imported memory is >= the initial declared size
    2) The maximal size of the imported memory is <= the maximal declared size
    
    The effective maximal limit will be min(imported_max, declared_max),
    hence the optimization will only trigger if the imported memory is
    already as large as it can be.
    
    Since memory growth is impossible, there is no point in reloading the
    environment anyway.
    
    Change-Id: Ie6c6ad278175d253b61131972a6db7530bd52b90
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3412082Reviewed-by: 's avatarClemens Backes <clemensb@chromium.org>
    Commit-Queue: Clemens Backes <clemensb@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#78782}
    a537cb6a
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