1 | //===-- examples/HowToUseJIT/HowToUseJIT.cpp - An example use of the JIT --===// |
2 | // |
3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
4 | // See https://llvm.org/LICENSE.txt for license information. |
5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
6 | // |
7 | //===----------------------------------------------------------------------===// |
8 | // |
9 | // WARNING: This example demonstrates how to use LLVM's older ExecutionEngine |
10 | // JIT APIs. The newer LLJIT APIs should be preferred for new |
11 | // projects. See llvm/examples/HowToUseLLJIT. |
12 | // |
13 | // This small program provides an example of how to quickly build a small |
14 | // module with two functions and execute it with the JIT. |
15 | // |
16 | // Goal: |
17 | // The goal of this snippet is to create in the memory |
18 | // the LLVM module consisting of two functions as follow: |
19 | // |
20 | // int add1(int x) { |
21 | // return x+1; |
22 | // } |
23 | // |
24 | // int foo() { |
25 | // return add1(10); |
26 | // } |
27 | // |
28 | // then compile the module via JIT, then execute the `foo' |
29 | // function and return result to a driver, i.e. to a "host program". |
30 | // |
31 | // Some remarks and questions: |
32 | // |
33 | // - could we invoke some code using noname functions too? |
34 | // e.g. evaluate "foo()+foo()" without fears to introduce |
35 | // conflict of temporary function name with some real |
36 | // existing function name? |
37 | // |
38 | //===----------------------------------------------------------------------===// |
39 | |
40 | #include "llvm/ADT/STLExtras.h" |
41 | #include "llvm/ExecutionEngine/ExecutionEngine.h" |
42 | #include "llvm/ExecutionEngine/GenericValue.h" |
43 | #include "llvm/ExecutionEngine/MCJIT.h" |
44 | #include "llvm/IR/Argument.h" |
45 | #include "llvm/IR/BasicBlock.h" |
46 | #include "llvm/IR/Constants.h" |
47 | #include "llvm/IR/DerivedTypes.h" |
48 | #include "llvm/IR/Function.h" |
49 | #include "llvm/IR/IRBuilder.h" |
50 | #include "llvm/IR/Instructions.h" |
51 | #include "llvm/IR/LLVMContext.h" |
52 | #include "llvm/IR/Module.h" |
53 | #include "llvm/IR/Type.h" |
54 | #include "llvm/Support/Casting.h" |
55 | #include "llvm/Support/ManagedStatic.h" |
56 | #include "llvm/Support/TargetSelect.h" |
57 | #include "llvm/Support/raw_ostream.h" |
58 | #include <algorithm> |
59 | #include <cassert> |
60 | #include <memory> |
61 | #include <vector> |
62 | |
63 | using namespace llvm; |
64 | |
65 | int main() { |
66 | InitializeNativeTarget(); |
67 | LLVMInitializeNativeAsmPrinter(); |
68 | |
69 | LLVMContext Context; |
70 | |
71 | // Create some module to put our function into it. |
72 | std::unique_ptr<Module> Owner = std::make_unique<Module>(args: "test" , args&: Context); |
73 | Module *M = Owner.get(); |
74 | |
75 | // Create the add1 function entry and insert this entry into module M. The |
76 | // function will have a return type of "int" and take an argument of "int". |
77 | Function *Add1F = |
78 | Function::Create(Ty: FunctionType::get(Result: Type::getInt32Ty(C&: Context), |
79 | Params: {Type::getInt32Ty(C&: Context)}, isVarArg: false), |
80 | Linkage: Function::ExternalLinkage, N: "add1" , M); |
81 | |
82 | // Add a basic block to the function. As before, it automatically inserts |
83 | // because of the last argument. |
84 | BasicBlock *BB = BasicBlock::Create(Context, Name: "EntryBlock" , Parent: Add1F); |
85 | |
86 | // Create a basic block builder with default parameters. The builder will |
87 | // automatically append instructions to the basic block `BB'. |
88 | IRBuilder<> builder(BB); |
89 | |
90 | // Get pointers to the constant `1'. |
91 | Value *One = builder.getInt32(C: 1); |
92 | |
93 | // Get pointers to the integer argument of the add1 function... |
94 | assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg |
95 | Argument *ArgX = &*Add1F->arg_begin(); // Get the arg |
96 | ArgX->setName("AnArg" ); // Give it a nice symbolic name for fun. |
97 | |
98 | // Create the add instruction, inserting it into the end of BB. |
99 | Value *Add = builder.CreateAdd(LHS: One, RHS: ArgX); |
100 | |
101 | // Create the return instruction and add it to the basic block |
102 | builder.CreateRet(V: Add); |
103 | |
104 | // Now, function add1 is ready. |
105 | |
106 | // Now we're going to create function `foo', which returns an int and takes no |
107 | // arguments. |
108 | Function *FooF = |
109 | Function::Create(Ty: FunctionType::get(Result: Type::getInt32Ty(C&: Context), Params: {}, isVarArg: false), |
110 | Linkage: Function::ExternalLinkage, N: "foo" , M); |
111 | |
112 | // Add a basic block to the FooF function. |
113 | BB = BasicBlock::Create(Context, Name: "EntryBlock" , Parent: FooF); |
114 | |
115 | // Tell the basic block builder to attach itself to the new basic block |
116 | builder.SetInsertPoint(BB); |
117 | |
118 | // Get pointer to the constant `10'. |
119 | Value *Ten = builder.getInt32(C: 10); |
120 | |
121 | // Pass Ten to the call to Add1F |
122 | CallInst *Add1CallRes = builder.CreateCall(Callee: Add1F, Args: Ten); |
123 | Add1CallRes->setTailCall(true); |
124 | |
125 | // Create the return instruction and add it to the basic block. |
126 | builder.CreateRet(V: Add1CallRes); |
127 | |
128 | // Now we create the JIT. |
129 | ExecutionEngine* EE = EngineBuilder(std::move(Owner)).create(); |
130 | |
131 | outs() << "We just constructed this LLVM module:\n\n" << *M; |
132 | outs() << "\n\nRunning foo: " ; |
133 | outs().flush(); |
134 | |
135 | // Call the `foo' function with no arguments: |
136 | std::vector<GenericValue> noargs; |
137 | GenericValue gv = EE->runFunction(F: FooF, ArgValues: noargs); |
138 | |
139 | // Import result of execution: |
140 | outs() << "Result: " << gv.IntVal << "\n" ; |
141 | delete EE; |
142 | llvm_shutdown(); |
143 | return 0; |
144 | } |
145 | |