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6ca59da244
From a user prospective, it forces the use of an annoying nullptr to mark the end of the vararg, and there's not type checking on the arguments. The variadic template is an obvious solution to both issues. Differential Revision: https://reviews.llvm.org/D31070 llvm-svn: 299949
138 lines
4.4 KiB
C++
138 lines
4.4 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 is distributed under the University of Illinois Open Source
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// 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/ADT/STLExtras.h"
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#include "llvm/ExecutionEngine/ExecutionEngine.h"
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#include "llvm/ExecutionEngine/GenericValue.h"
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#include "llvm/IR/Argument.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Type.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/ManagedStatic.h"
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#include "llvm/Support/TargetSelect.h"
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#include "llvm/Support/raw_ostream.h"
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#include <algorithm>
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#include <cassert>
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#include <memory>
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#include <vector>
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using namespace llvm;
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int main() {
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InitializeNativeTarget();
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LLVMContext Context;
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// Create some module to put our function into it.
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std::unique_ptr<Module> Owner = make_unique<Module>("test", Context);
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Module *M = Owner.get();
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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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Function *Add1F =
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cast<Function>(M->getOrInsertFunction("add1", Type::getInt32Ty(Context),
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Type::getInt32Ty(Context)));
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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 = BasicBlock::Create(Context, "EntryBlock", Add1F);
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// Create a basic block builder with default parameters. The builder will
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// automatically append instructions to the basic block `BB'.
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IRBuilder<> builder(BB);
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// Get pointers to the constant `1'.
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Value *One = builder.getInt32(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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Value *Add = builder.CreateAdd(One, ArgX);
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// Create the return instruction and add it to the basic block
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builder.CreateRet(Add);
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// Now, function add1 is ready.
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// Now we're 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::getInt32Ty(Context)));
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// Add a basic block to the FooF function.
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BB = BasicBlock::Create(Context, "EntryBlock", FooF);
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// Tell the basic block builder to attach itself to the new basic block
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builder.SetInsertPoint(BB);
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// Get pointer to the constant `10'.
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Value *Ten = builder.getInt32(10);
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// Pass Ten to the call to Add1F
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CallInst *Add1CallRes = builder.CreateCall(Add1F, Ten);
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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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builder.CreateRet(Add1CallRes);
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// Now we create the JIT.
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ExecutionEngine* EE = EngineBuilder(std::move(Owner)).create();
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outs() << "We just constructed this LLVM module:\n\n" << *M;
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outs() << "\n\nRunning foo: ";
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outs().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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outs() << "Result: " << gv.IntVal << "\n";
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delete EE;
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llvm_shutdown();
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return 0;
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}
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