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// Copyright 2020 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.
#include <src/heap/base/stack.h>
// Save all callee-saved registers in the specified buffer.
// extern "C" void SaveCalleeSavedRegisters(intptr_t* buffer);
// See asm/x64/save_registers_asm.cc for why the function is not generated
// using clang.
//
// Do not depend on V8_TARGET_OS_* defines as some embedders may override the
// GN toolchain (e.g. ChromeOS) and not provide them.
//
// The following assumes cdecl calling convention.
// Source: https://en.wikipedia.org/wiki/X86_calling_conventions#cdecl
// 3 32-bit registers = 3 intprt_t
static_assert(heap::base::Stack::NumberOfCalleeSavedRegisters == 3,
"Mismatch in the number of callee-saved registers");
static_assert(sizeof(intptr_t) == 4, "Mismatch in word size");
asm(
#ifdef _WIN32
".globl _SaveCalleeSavedRegisters \n"
"_SaveCalleeSavedRegisters: \n"
#else // !_WIN32
".globl SaveCalleeSavedRegisters \n"
".type SaveCalleeSavedRegisters, %function \n"
".hidden SaveCalleeSavedRegisters \n"
"SaveCalleeSavedRegisters: \n"
#endif // !_WIN32
// 8: [ intptr_t* buffer ]
// 4: [ ret ]
// 0: [ saved %ebp ]
// %ebp is callee-saved. Maintain proper frame pointer for debugging.
" push %ebp \n"
" movl %esp, %ebp \n"
// Load the buffer's address in %ecx.
" movl 8(%ebp), %ecx \n"
// Save the callee-saved registers.
" movl %ebx, 0(%ecx) \n"
" movl %esi, 4(%ecx) \n"
" movl %edi, 8(%ecx) \n"
// Restore %ebp as it was used as frame pointer and return.
" pop %ebp \n"
" ret \n");
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