Source/JavaScriptCore/assembler/MaxFrameExtentForSlowPathCall.h

/*
 * Copyright (C) 2013, 2016 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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#pragma once

#include "Register.h"
#include "StackAlignment.h"
#include <wtf/Assertions.h>

namespace JSC {

// The maxFrameExtentForSlowPathCall is the max amount of stack space (in bytes)
// that can be used for outgoing args when calling a slow path C function
// from JS code.

#if !ENABLE(ASSEMBLER)
static constexpr size_t maxFrameExtentForSlowPathCall = 0;

#elif CPU(X86_64) && OS(WINDOWS)
// 4 args in registers, but stack space needs to be allocated for all args.
static constexpr size_t maxFrameExtentForSlowPathCall = 64;

#elif CPU(X86_64)
// All args in registers.
static constexpr size_t maxFrameExtentForSlowPathCall = 0;

#elif CPU(X86)
// 7 args on stack (28 bytes).
static constexpr size_t maxFrameExtentForSlowPathCall = 40;

#elif CPU(ARM64) || CPU(ARM64E) || CPU(RISCV64)
// All args in registers.
static constexpr size_t maxFrameExtentForSlowPathCall = 0;

#elif CPU(ARM)
// First four args in registers, remaining 4 args on stack.
static constexpr size_t maxFrameExtentForSlowPathCall = 24;

#elif CPU(MIPS)
// Though args are in registers, there need to be space on the stack for all args.
static constexpr size_t maxFrameExtentForSlowPathCall = 40;

#else
#error "Unsupported CPU: need value for maxFrameExtentForSlowPathCall"

#endif

static_assert(!(maxFrameExtentForSlowPathCall % sizeof(Register)), "Extent must be in multiples of registers");

#if ENABLE(ASSEMBLER)
// Make sure that cfr - maxFrameExtentForSlowPathCall bytes will make the stack pointer aligned
static_assert((maxFrameExtentForSlowPathCall % 16) == 16 - sizeof(CallerFrameAndPC), "Extent must align stack from callframe pointer");
#endif

static constexpr size_t maxFrameExtentForSlowPathCallInRegisters = maxFrameExtentForSlowPathCall / sizeof(Register);

} // namespace JSC