• Ross McIlroy's avatar
    [Turboprop] Move deoptimizations for dynamic map checks into builtin. · b6643320
    Ross McIlroy authored
    In order to reduce the codegen size of dynamic map checks, add the
    ability to have an eager with resume deopt point, which can call
    a given builitin to perform a more detailed check than can be done
    in codegen, and then either deoptimizes itself (as if the calling
    code had performed an eager deopt) or resumes execution in the
    calling code after the check.
    
    In addition, support for adding extra arguments to a
    deoptimization continuation is added to enable us to pass the
    necessary arguments to the DynamicMapChecks builtin.
    
    Finally, a trampoline is added to the DynamicMapChecks which saves
    the registers that might be clobbered by that builtin, to avoid
    having to save them in the generated code. This trampoline also
    performs the deoptimization based on the result of the
    DynamicMapChecks builtin.
    
    In order to ensure both the trampoline and DynamicMapChecks
    builtin have the same call interface, and to limit the number
    of registers that need saving in the trampoline, the
    DynamicMapChecks builtin is moved to be a CSA builtin with a
    custom CallInterfaceDescriptor, that calls an exported Torque
    macro that implements the actual functionality.
    
    All told, this changes the codegen for a monomorphic dynamic
    map check from:
        movl rbx,<expected_map>
        cmpl [<object>-0x1],rbx
        jnz <deferred_call>
       resume_point:
        ...
       deferred_call:
        <spill registers>
        movl rax,<slot>
        movq rbx,<object>
        movq rcx,<handler>
        movq r10,<DynamicMapChecks>
        call r10
        cmpq rax,0x0
        jz <restore_regs>
        cmpq rax,0x1
        jz <deopt_point_1>
        cmpq rax,0x2
        jz <deopt_point_2>
        int3l
       restore_regs:
        <restore_regs>
        jmp <resume_point>
        ...
       deopt_point_1:
        call Deoptimization_Eager
       deopt_point_2:
        call Deoptimization_Bailout
    
    To: movl rax,<slot>
        movl rcx,<expected_map>
        movq rdx,<handler>
        cmpl [<object>-0x1],rcx
        jnz <deopt_point>
       resume_point:
        ...
       deopt_point:
        call DynamicMapChecksTrampoline
        jmp <resume_point>
    
    BUG=v8:10582
    
    Change-Id: Ica4927b9acc963b9b73dc62d9379a7815335650f
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2560197
    Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
    Reviewed-by: 's avatarGeorg Neis <neis@chromium.org>
    Reviewed-by: 's avatarJakob Gruber <jgruber@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#71545}
    b6643320
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