src/builtins/frame-arguments.tq

// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

@export
struct Arguments {
  const frame: FrameWithArguments;
  const base: RawPtr;
  const length: intptr;
}

extern operator '[]' macro GetArgumentValue(Arguments, intptr): JSAny;
extern macro GetFrameArguments(FrameWithArguments, intptr): Arguments;

struct ArgumentsIterator {
  macro Next(): Object labels NoMore {
    if (this.current == this.arguments.length) goto NoMore;
    return this.arguments[this.current++];
  }
  const arguments: Arguments;
  current: intptr;
}

struct FrameWithArgumentsInfo {
  const frame: FrameWithArguments;
  const argument_count: bint;
  const formal_parameter_count: bint;
}

// Calculates and returns the frame pointer, argument count and formal
// parameter count to be used to access a function's parameters, taking
// argument adapter frames into account.
//
// TODO(danno):
// This macro is should only be used in builtins that can be called from
// interpreted or JITted code, not from CSA/Torque builtins (the number of
// returned formal parameters would be wrong).
// It is difficult to actually check/assert this, since interpreted or JITted
// frames are StandardFrames, but so are hand-written builtins. Doing that
// more refined check would be prohibitively expensive.
macro GetFrameWithArgumentsInfo(implicit context: Context)():
    FrameWithArgumentsInfo {
  const frame =
      Cast<StandardFrame>(LoadParentFramePointer()) otherwise unreachable;
  const f: JSFunction = frame.function;

  const shared: SharedFunctionInfo = f.shared_function_info;
  const formalParameterCount: bint =
      Convert<bint>(Convert<int32>(shared.formal_parameter_count));
  const argumentCount: bint = formalParameterCount;

  const adaptor = Cast<ArgumentsAdaptorFrame>(frame.caller)
      otherwise return FrameWithArgumentsInfo{
    frame,
    argument_count: argumentCount,
    formal_parameter_count: formalParameterCount
  };

  return FrameWithArgumentsInfo{
    frame: adaptor,
    argument_count: Convert<bint>(adaptor.length),
    formal_parameter_count: formalParameterCount
  };
}