allkern/LJL

A JIT function generator written in C++

LJL (Lycoder's JIT Library)

LJL is a simple x86-64 JIT function generation library written in C++17 that is compatible with STL containters, std::thread, etc. As of now, mainly intended to be used on emulators, or as a learning tool, either of JIT code generation, or Assembly. Check the wiki for tutorials, and further information about LJL!

Short/medium term goals

• Create an "extensions" system that allows developers to choose whether some feature is included in a project or not, making performance-critical, or low-resource development easier (work being done in the development branch)
• Make debugging easier by creating assemblers, disassemblers, and a runtime (as extensions)

Long term goals

• Become the code generation library of choice in at least one of the following fields:
  • Performance-critical/low-resource development
  • JIT Compilers
  • Emulators
  • Teaching assembly/JIT code generation

Simple example (Windows)

#include <iostream>
#include <array>

#include "LJL\ljl.h"

int main() {
	// Create a function, and builder with return type <void>
	ljl::Function <void> myFunction;
	ljl::Builder myBuilder(myFunction);
	
	// Create an STL array
	std::array <int, 10> myArray = { 0 };

	// Create an address from a pointer to an array
	ljl::Address myAddress(myArray.data());
  	
        // Code:
        // movabs rax         , myAddress
        // mov    rcx         , 0x1
        // mov    [rax+rcx*4] , 0xcafe
  
	myBuilder.append( {
		0x48, 0xb8                    
	} );

	myBuilder.append(myAddress);

	myBuilder.append( {
		0x48, 0xc7, 0xc1
	} );

	myBuilder.append((ljl::u32)0x1);
  
  
	myBuilder.append( {
		0x48, 0xC7, 0x04, 0x88
	} );

	myBuilder.append((ljl::u32)0xcafe);

	// Append prolog and make the page executable
	myBuilder.make();

	// Call the generated function
	myFunction();

	// Print the array
	size_t p = 0;
	for (int a : myArray) {
		std::cout << "myArray[" << p++ << "] = " << std::hex << a << std::endl;
	}
	system("pause");
	return 0;
}