Created
December 28, 2013 17:57
-
-
Save tomas789/8162150 to your computer and use it in GitHub Desktop.
LLVM JIT Example - Example of very simple JIT using LLVM. It compiles function with prototype `int64_t()` returning value `765`. Build: clang++ `llvm-config --cppflags --ldflags --libs core jit X86` jit.cpp
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
#include <iostream> | |
#include <cstdint> | |
#include <string> | |
#include "llvm/ExecutionEngine/JIT.h" | |
#include "llvm/IR/IRBuilder.h" | |
#include "llvm/IR/Module.h" | |
#include "llvm/PassManager.h" | |
#include "llvm/Support/TargetSelect.h" | |
#include "llvm/Analysis/Verifier.h" | |
using namespace llvm; | |
int main(int argc, char * argv[]) { | |
InitializeNativeTarget(); | |
/* LLVM Global Context */ | |
LLVMContext & ctx = getGlobalContext(); | |
/* Module */ | |
Module * module = new Module("MyModule", ctx); | |
/* IRBuilder */ | |
IRBuilder<> builder(ctx); | |
/* Create execution engine */ | |
std::string err_str; | |
ExecutionEngine * engine = EngineBuilder(module).setErrorStr(&err_str).create(); | |
if (!engine) { | |
std::cerr << "Could not create ExecutionEngine:" | |
<< err_str << std::endl; | |
return 1; | |
} | |
/* Type of value I want to return - 64-bit integer */ | |
IntegerType * int64_ty = Type::getInt64Ty(ctx); | |
/* Actual value to return */ | |
int64_t value = 765; | |
/* LLVM Value */ | |
Value * v = ConstantInt::get(int64_ty, value); | |
/* Create prototype of result function - int64_t() */ | |
std::vector<Type *> arguments; | |
FunctionType * proto = FunctionType::get(int64_ty, arguments, false); | |
/* Create function body */ | |
Function * fce = Function::Create(proto, Function::ExternalLinkage, "MyFunction", module); | |
BasicBlock * bb = BasicBlock::Create(ctx, "entry", fce); | |
/* Point builder to add instructions to function body */ | |
builder.SetInsertPoint(bb); | |
/* Return value */ | |
builder.CreateRet(v); | |
/* Function pass manager */ | |
FunctionPassManager pass_manager(module); | |
/* Add data layout */ | |
pass_manager.add(new DataLayout(*engine->getDataLayout())); | |
pass_manager.doInitialization(); | |
/* Do optimizations */ | |
pass_manager.run(*fce); | |
/* JIT it */ | |
void * fce_ptr = engine->getPointerToFunction(fce); | |
int64_t (*fce_typed_ptr)() = (int64_t(*)())fce_ptr; | |
/* Excute JITed function */ | |
std::cout << "Result: " << (*fce_typed_ptr)() | |
<< std::endl << std::endl; | |
/* Dump LLVM IR */ | |
std::cout << "LLVM IR dump: " << std::endl; | |
module->dump(); | |
return 0; | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment