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113 lines
3.8 KiB
C++
113 lines
3.8 KiB
C++
//===-- examples/HowToUseJIT/HowToUseJIT.cpp - An example use of the JIT --===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Valery A. Khamenya and is distributed under the
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// University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This small program provides an example of how to quickly build a small
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// module with two functions and execute it with the JIT.
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//
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// Goal:
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// The goal of this snippet is to create in the memory
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// the LLVM module consisting of two functions as follow:
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//
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// int add1(int x) {
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// return x+1;
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// }
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//
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// int foo() {
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// return add1(10);
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// }
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//
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// then compile the module via JIT, then execute the `foo'
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// function and return result to a driver, i.e. to a "host program".
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//
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// Some remarks and questions:
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//
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// - could we invoke some code using noname functions too?
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// e.g. evaluate "foo()+foo()" without fears to introduce
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// conflict of temporary function name with some real
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// existing function name?
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Module.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/ModuleProvider.h"
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#include "llvm/ExecutionEngine/JIT.h"
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#include "llvm/ExecutionEngine/Interpreter.h"
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#include "llvm/ExecutionEngine/GenericValue.h"
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#include <iostream>
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using namespace llvm;
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int main() {
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// Create some module to put our function into it.
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Module *M = new Module("test");
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// Create the add1 function entry and insert this entry into module M. The
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// function will have a return type of "int" and take an argument of "int".
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// The '0' terminates the list of argument types.
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Function *Add1F =
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cast<Function>(M->getOrInsertFunction("add1", Type::Int32Ty, Type::Int32Ty,
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(Type *)0));
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// Add a basic block to the function. As before, it automatically inserts
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// because of the last argument.
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BasicBlock *BB = new BasicBlock("EntryBlock", Add1F);
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// Get pointers to the constant `1'.
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Value *One = ConstantInt::get(Type::Int32Ty, 1);
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// Get pointers to the integer argument of the add1 function...
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assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
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Argument *ArgX = Add1F->arg_begin(); // Get the arg
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ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
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// Create the add instruction, inserting it into the end of BB.
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Instruction *Add = BinaryOperator::createAdd(One, ArgX, "addresult", BB);
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// Create the return instruction and add it to the basic block
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new ReturnInst(Add, BB);
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// Now, function add1 is ready.
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// Now we going to create function `foo', which returns an int and takes no
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// arguments.
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Function *FooF =
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cast<Function>(M->getOrInsertFunction("foo", Type::Int32Ty, (Type *)0));
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// Add a basic block to the FooF function.
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BB = new BasicBlock("EntryBlock", FooF);
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// Get pointers to the constant `10'.
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Value *Ten = ConstantInt::get(Type::Int32Ty, 10);
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// Pass Ten to the call call:
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CallInst *Add1CallRes = new CallInst(Add1F, Ten, "add1", BB);
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Add1CallRes->setTailCall(true);
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// Create the return instruction and add it to the basic block.
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new ReturnInst(Add1CallRes, BB);
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// Now we create the JIT.
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ExistingModuleProvider* MP = new ExistingModuleProvider(M);
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ExecutionEngine* EE = ExecutionEngine::create(MP, false);
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std::cout << "We just constructed this LLVM module:\n\n" << *M;
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std::cout << "\n\nRunning foo: " << std::flush;
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// Call the `foo' function with no arguments:
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std::vector<GenericValue> noargs;
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GenericValue gv = EE->runFunction(FooF, noargs);
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// Import result of execution:
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std::cout << "Result: " << gv.IntVal.toString(10) << "\n";
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return 0;
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}
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