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102 lines
3.4 KiB
C++
102 lines
3.4 KiB
C++
//===------- HowToUseLLJIT.cpp - An example use of ORC-based LLJIT --------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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 a 'add1' function and use of IRBuilder to create add & return
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// instructions.
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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 a function 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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// add1(42);
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//
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// then compile the module via LLJIT, then execute the 'add1'
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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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//===----------------------------------------------------------------------===//
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#include "llvm/ExecutionEngine/Orc/LLJIT.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/Module.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/InitLLVM.h"
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#include "llvm/Support/TargetSelect.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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using namespace llvm::orc;
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ExitOnError ExitOnErr;
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ThreadSafeModule createDemoModule() {
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auto Context = std::make_unique<LLVMContext>();
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auto M = std::make_unique<Module>("test", *Context);
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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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Function::Create(FunctionType::get(Type::getInt32Ty(*Context),
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{Type::getInt32Ty(*Context)}, false),
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Function::ExternalLinkage, "add1", M.get());
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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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return ThreadSafeModule(std::move(M), std::move(Context));
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}
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int main(int argc, char *argv[]) {
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// Initialize LLVM.
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InitLLVM X(argc, argv);
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InitializeNativeTarget();
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InitializeNativeTargetAsmPrinter();
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cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");
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ExitOnErr.setBanner(std::string(argv[0]) + ": ");
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// Create an LLJIT instance.
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auto J = ExitOnErr(LLJITBuilder().create());
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auto M = createDemoModule();
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ExitOnErr(J->addIRModule(std::move(M)));
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// Look up the JIT'd function, cast it to a function pointer, then call it.
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auto Add1Sym = ExitOnErr(J->lookup("add1"));
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int (*Add1)(int) = (int (*)(int))Add1Sym.getAddress();
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int Result = Add1(42);
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outs() << "add1(42) = " << Result << "\n";
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return 0;
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}
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