• Leszek Swirski's avatar
    Reland "[codegen] Add static interface descriptors" · 2871e05c
    Leszek Swirski authored
    This is a reland of ae0752df
    
    Reland fixes:
    
      * Remove UNREACHABLE() from constexpr switch, since we don't have a
        CONSTEXPR_UNREACHABLE() (it's ok, the switch is exhaustive for the
        enum anyway).
      * Fix IsRegisterArray trait to use public inheritance and size_t for
        std::array size.
    
    Original change's description:
    > [codegen] Add static interface descriptors
    >
    > Add a new CRTP StaticCallInterfaceDescriptor class, which provides
    > static constexpr getters for a descriptor's registers, parameter counts,
    > and so on. Each CallInterfaceDescriptor subclass is changed to extend
    > StaticCallInterfaceDescriptor, with StaticCallInterfaceDescriptor itself
    > extending CallInterfaceDescriptor to still provide a dynamic lookup
    > where needed.
    >
    > StaticCallInterfaceDescriptor provides a couple of customisation points,
    > where it reads its CRTP derived descriptor's static fields and
    > functions, with default fallbacks where appropriate. With these
    > customisation points, the definition of CallInterfaceDescriptor
    > subclasses is simplified to:
    >
    >     a) Providing parameter names (as before)
    >     b) Providing parameter types (as before)
    >     c) Optionally setting flags (like kNoContext or kAllowVarArgs) as
    >        static booleans on the class.
    >     d) Optionally providing a `registers()` method that returns a
    >        std::array<Register, N> of registers that may be used for
    >        parameters (if not provided, this defaults to the implementation
    >        specific default register set).
    >
    > Parameter registers (and register count) are automagically set based on
    > the number of parameters and number of given registers, with extra magic
    > to ignore no_reg registers (to reduce ia32 special casing). The
    > CallInterfaceDescriptorData is initialized based on these static
    > functions, rather than manual per-descriptor initializers.
    >
    > This allows us to skip loading descriptors dynamically for CallBuiltin
    > in Sparkplug, and instead lets us use a bit of template magic to
    > statically set up arguments for the calls. Any other users of statically
    > known descriptors will also benefit, thanks to C++ picking the static
    > methods over the dynamic methods on the base class when available.
    >
    > Because we can remove various virtual functions and trigger heavier
    > inlining of constantly known values, binary size slightly decreases with
    > this change.
    >
    > Note that torque-generated descriptors are changed to use the same magic,
    > rather than having Torque-specific magic, for consistency.
    >
    > Bug: v8:11420
    > Change-Id: Icc5e238b6313a08734feb564204a13226b450c22
    > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2814518
    > Auto-Submit: Leszek Swirski <leszeks@chromium.org>
    > Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
    > Reviewed-by: Clemens Backes <clemensb@chromium.org>
    > Reviewed-by: Igor Sheludko <ishell@chromium.org>
    > Reviewed-by: Jakob Gruber <jgruber@chromium.org>
    > Commit-Queue: Clemens Backes <clemensb@chromium.org>
    > Cr-Commit-Position: refs/heads/master@{#73996}
    
    TBR=nicohartmann@chromium.org,clemensb@chromium.org,ishell@chromium.org,clemensb@chromium.org
    
    Bug: v8:11420
    Change-Id: Icd1f6cdb3c178e74460044b1e9623139929ceba8
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2831872Reviewed-by: 's avatarLeszek Swirski <leszeks@chromium.org>
    Reviewed-by: 's avatarClemens Backes <clemensb@chromium.org>
    Reviewed-by: 's avatarIgor Sheludko <ishell@chromium.org>
    Commit-Queue: Leszek Swirski <leszeks@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#74010}
    2871e05c
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