LLVM（1）Fibonacci实例

#include <algorithm>
#include <cstdlib>
#include <memory>
#include <string>
#include <vector>
#include <iostream>

using namespace std;

int fib(int x)
{


	if (x <= 2)
		return 1;


	return fib(x - 1) + fib(x - 2);



}

int main(int argc, char **argv)
{
	int n = argc > 1 ? atol(argv[1]) : 24;

	cout << "Result: " << fib(n) << "\n";
}

static Function *CreateFibFunction(Module *M, LLVMContext &Context)
{
	// Create the fib function and insert it into module M. This function is said
	// to return an int and take an int parameter.
	FunctionType *FibFTy = FunctionType::get(Type::getInt32Ty(Context),
											 {Type::getInt32Ty(Context)}, false);
	Function *FibF =
		Function::Create(FibFTy, Function::ExternalLinkage, "fib", M);

	// Add a basic block to the function.
	BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", FibF);

	// Get pointers to the constants.
	Value *One = ConstantInt::get(Type::getInt32Ty(Context), 1);
	Value *Two = ConstantInt::get(Type::getInt32Ty(Context), 2);

	// Get pointer to the integer argument of the add1 function...
	Argument *ArgX = &*FibF->arg_begin(); // Get the arg.
	ArgX->setName("AnArg");				  // Give it a nice symbolic name for fun.

	// Create the true_block.
	BasicBlock *RetBB = BasicBlock::Create(Context, "return", FibF);
	// Create an exit block.
	BasicBlock *RecurseBB = BasicBlock::Create(Context, "recurse", FibF);

	// Create the "if (arg <= 2) goto exitbb"
	Value *CondInst = new ICmpInst(*BB, ICmpInst::ICMP_SLE, ArgX, Two, "cond");
	BranchInst::Create(RetBB, RecurseBB, CondInst, BB);

	// Create: ret int 1
	ReturnInst::Create(Context, One, RetBB);

	// create fib(x-1)
	Value *Sub = BinaryOperator::CreateSub(ArgX, One, "arg", RecurseBB);
	CallInst *CallFibX1 = CallInst::Create(FibF, Sub, "fibx1", RecurseBB);
	CallFibX1->setTailCall();

	// create fib(x-2)
	Sub = BinaryOperator::CreateSub(ArgX, Two, "arg", RecurseBB);
	CallInst *CallFibX2 = CallInst::Create(FibF, Sub, "fibx2", RecurseBB);
	CallFibX2->setTailCall();

	// fib(x-1)+fib(x-2)
	Value *Sum = BinaryOperator::CreateAdd(CallFibX1, CallFibX2,
										   "addresult", RecurseBB);

	// Create the return instruction and add it to the basic block
	ReturnInst::Create(Context, Sum, RecurseBB);

	return FibF;
}

/*
 * clang++ t1.cpp `llvm-config --cxxflags --ldflags --system-libs --libs all` -o t1
 *
 *
 *
 */

//===--- examples/Fibonacci/fibonacci.cpp - An example use of the JIT -----===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This small program provides an example of how to build quickly a small module
// with function Fibonacci and execute it with the JIT.
//
// The goal of this snippet is to create in the memory the LLVM module
// consisting of one function as follow:
//
//   int fib(int x) {
//     if(x<=2) return 1;
//     return fib(x-1)+fib(x-2);
//   }
//
// Once we have this, we compile the module via JIT, then execute the `fib'
// function and return result to a driver, i.e. to a "host program".
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/APInt.h"
#include "llvm/IR/Verifier.h"
#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/ExecutionEngine/MCJIT.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cstdlib>
#include <memory>
#include <string>
#include <vector>

using namespace llvm;

static Function *CreateFibFunction(Module *M, LLVMContext &Context)
{
	// Create the fib function and insert it into module M. This function is said
	// to return an int and take an int parameter.
	FunctionType *FibFTy = FunctionType::get(Type::getInt32Ty(Context),
											 {Type::getInt32Ty(Context)}, false);
	Function *FibF =
		Function::Create(FibFTy, Function::ExternalLinkage, "fib", M);

	// Add a basic block to the function.
	BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", FibF);

	// Get pointers to the constants.
	Value *One = ConstantInt::get(Type::getInt32Ty(Context), 1);
	Value *Two = ConstantInt::get(Type::getInt32Ty(Context), 2);

	// Get pointer to the integer argument of the add1 function...
	Argument *ArgX = &*FibF->arg_begin(); // Get the arg.
	ArgX->setName("AnArg");				  // Give it a nice symbolic name for fun.

	// Create the true_block.
	BasicBlock *RetBB = BasicBlock::Create(Context, "return", FibF);
	// Create an exit block.
	BasicBlock *RecurseBB = BasicBlock::Create(Context, "recurse", FibF);

	// Create the "if (arg <= 2) goto exitbb"
	Value *CondInst = new ICmpInst(*BB, ICmpInst::ICMP_SLE, ArgX, Two, "cond");
	BranchInst::Create(RetBB, RecurseBB, CondInst, BB);

	// Create: ret int 1
	ReturnInst::Create(Context, One, RetBB);

	// create fib(x-1)
	Value *Sub = BinaryOperator::CreateSub(ArgX, One, "arg", RecurseBB);
	CallInst *CallFibX1 = CallInst::Create(FibF, Sub, "fibx1", RecurseBB);
	CallFibX1->setTailCall();

	// create fib(x-2)
	Sub = BinaryOperator::CreateSub(ArgX, Two, "arg", RecurseBB);
	CallInst *CallFibX2 = CallInst::Create(FibF, Sub, "fibx2", RecurseBB);
	CallFibX2->setTailCall();

	// fib(x-1)+fib(x-2)
	Value *Sum = BinaryOperator::CreateAdd(CallFibX1, CallFibX2,
										   "addresult", RecurseBB);

	// Create the return instruction and add it to the basic block
	ReturnInst::Create(Context, Sum, RecurseBB);

	return FibF;
}

int main(int argc, char **argv)
{
	int n = argc > 1 ? atol(argv[1]) : 24;

	InitializeNativeTarget();
	InitializeNativeTargetAsmPrinter();
	LLVMContext Context;

	// Create some module to put our function into it.
	std::unique_ptr<Module> Owner(new Module("test", Context));
	Module *M = Owner.get();

	// We are about to create the "fib" function:
	Function *FibF = CreateFibFunction(M, Context);

	// Now we going to create JIT
	std::string errStr;
	ExecutionEngine *EE =
		EngineBuilder(std::move(Owner))
			.setErrorStr(&errStr)
			.create();

	if (!EE)
	{
		errs() << argv[0] << ": Failed to construct ExecutionEngine: " << errStr
			   << "\n";
		return 1;
	}

	errs() << "verifying... ";
	if (verifyModule(*M))
	{
		errs() << argv[0] << ": Error constructing function!\n";
		return 1;
	}

	errs() << "OK\n";
	errs() << "We just constructed this LLVM module:\n\n---------\n"
		   << *M;
	errs() << "---------\nstarting fibonacci(" << n << ") with JIT...\n";

	// Call the Fibonacci function with argument n:
	std::vector<GenericValue> Args(1);
	Args[0].IntVal = APInt(32, n);
	GenericValue GV = EE->runFunction(FibF, Args);

	// import result of execution
	outs() << "Result: " << GV.IntVal << "\n";

	return 0;
}

#include <algorithm>
#include <cstdlib>
#include <memory>
#include <string>
#include <vector>
#include <iostream>

using namespace std;

int fib(int x)
{


	if (x <= 2)
		return 1;


	return fib(x - 1) + fib(x - 2);



}

int main(int argc, char **argv)
{
	int n = argc > 1 ? atol(argv[1]) : 24;

	cout << "Result: " << fib(n) << "\n";
}

CC1 = clang++ -stdlib=libstdc++
CC2 = g++
# CFLAGS = -g -O0
CFLAGS = -O3
LLVM_C_FLAGS = `llvm-config --cxxflags`
LLVM_L_FLAGS = `llvm-config --ldflags --system-libs --libs all`

.PHONY: t1

t1: t1.o
	${CC1} $< ${CFLAGS} ${LLVM_L_FLAGS} -o $@

t2: t2.o
	${CC2} $< ${CFLAGS} -o $@

clean:
	rm -r t1.o t1 t2.o t2

t1.o: t1.cpp
	${CC1} ${CFLAGS} ${LLVM_C_FLAGS} -c $< -o $@

t2.o: t2.cpp
	${CC2} -c $< ${CFLAGS} -o $@

# wrong: clang++ t1.o `llvm-config --cxxflags --ldflags --system-libs --libs all` -o t1
# right: clang++ `llvm-config --cxxflags --ldflags --system-libs --libs all`  t1.o -o t1