jit介绍以及使用
22 Mar 2019
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JIT概念就不说了
通过这个教程了解jit，https://solarianprogrammer.com/2018/01/12/writing-minimal-x86-64-jit-compiler-cpp-part-2/
代码在这里 https://github.com/sol-prog/x86-64-minimal-JIT-compiler-Cpp/blob/master/part_2/funcall.cpp
一个调用的汇编是这样的
func():
push rbp
mov rbp, rsp
call test()
pop rbp
ret
call这个动作要通过代码来实现
func():
push rbp
mov rbp, rsp
movabs rax, 0x0 # replace with the address of the called function
call rax
pop rbp
ret
抄到机器码
0: 55 push rbp
1: 48 89 e5 mov rbp,rsp
4: 48 b8 00 00 00 00 00 movabs rax,0x0
b: 00 00 00
e: ff d0 call rax
10: 5d pop rbp
11: c3 ret
注意48 b8 ff d0
封装成函数来保存入站出站
namespace AssemblyChunks {
std::vector<uint8_t>function_prologue {
0x55, // push rbp
0x48, 0x89, 0xe5, // mov rbp, rsp
};
std::vector<uint8_t>function_epilogue {
0x5d, // pop rbp
0xc3 // ret
};
}
最终运行时变成这样
MemoryPages mp;
// Push prologue
mp.push(AssemblyChunks::function_prologue);
// Push the call to the C++ function test (actually we push the address of the test function)
mp.push(0x48); mp.push(0xb8); mp.push(test); // movabs rax, <function_address>
mp.push(0xff); mp.push(0xd0); // call rax
// Push epilogue and print the generated code
mp.push(AssemblyChunks::function_epilogue);
mp.show_memory();
能调用内部，也就能调用写好的函数，更进一步，调用外部输入函数
以及通过下面这些链接学一下，争取抄一个
https://www.clarkok.com/blog/2016/06/13/%E4%BD%BF%E7%94%A8-Xbyak-%E8%BF%9B%E8%A1%8C-JIT/
https://github.com/clarkok/cyan/blob/master/lib/codegen_x64.cpp
https://www.clarkok.com/blog/2016/04/20/Cript%E4%B8%80%E9%97%A8%E8%84%9A%E6%9C%AC%E8%AF%AD%E8%A8%80/
https://github.com/taocpp/PEGTL/blob/66e982bc2baef027fa463e6d633b5a8bcaae9f00/examples/calculator.cc
