1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
//===--- examples/Fibonacci/fibonacci.cpp - An example use of the JIT -----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// 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/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Analysis/Verifier.h"
#include "llvm/ExecutionEngine/JIT.h"
#include "llvm/ExecutionEngine/Interpreter.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/TargetSelect.h"
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.
Function *FibF =
cast<Function>(M->getOrInsertFunction("fib", Type::getInt32Ty(Context),
Type::getInt32Ty(Context),
(Type *)0));
// 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();
LLVMContext Context;
// Create some module to put our function into it.
OwningPtr<Module> M(new Module("test", Context));
// We are about to create the "fib" function:
Function *FibF = CreateFibFunction(M.get(), Context);
// Now we going to create JIT
std::string errStr;
ExecutionEngine *EE =
EngineBuilder(M.get())
.setErrorStr(&errStr)
.setEngineKind(EngineKind::JIT)
.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;
}
|
