examples/HowToUseLLJIT/HowToUseLLJIT.cpp

   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 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
  10 #include "llvm/IR/Function.h"
  11 #include "llvm/IR/IRBuilder.h"
  12 #include "llvm/IR/Module.h"
  13 #include "llvm/Support/InitLLVM.h"
  14 #include "llvm/Support/TargetSelect.h"
  15 #include "llvm/Support/raw_ostream.h"
  16
  17 using namespace llvm;
  18 using namespace llvm::orc;
  19
  20 ExitOnError ExitOnErr;
  21
  22 ThreadSafeModule createDemoModule() {
  23   auto Context = std::make_unique<LLVMContext>();
  24   auto M = std::make_unique<Module>("test", *Context);
  25
  26   // Create the add1 function entry and insert this entry into module M.  The
  27   // function will have a return type of "int" and take an argument of "int".
  28   Function *Add1F =
  29       Function::Create(FunctionType::get(Type::getInt32Ty(*Context),
  30                                          {Type::getInt32Ty(*Context)}, false),
  31                        Function::ExternalLinkage, "add1", M.get());
  32
  33   // Add a basic block to the function. As before, it automatically inserts
  34   // because of the last argument.
  35   BasicBlock *BB = BasicBlock::Create(*Context, "EntryBlock", Add1F);
  36
  37   // Create a basic block builder with default parameters.  The builder will
  38   // automatically append instructions to the basic block `BB'.
  39   IRBuilder<> builder(BB);
  40
  41   // Get pointers to the constant `1'.
  42   Value *One = builder.getInt32(1);
  43
  44   // Get pointers to the integer argument of the add1 function...
  45   assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
  46   Argument *ArgX = &*Add1F->arg_begin();          // Get the arg
  47   ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
  48
  49   // Create the add instruction, inserting it into the end of BB.
  50   Value *Add = builder.CreateAdd(One, ArgX);
  51
  52   // Create the return instruction and add it to the basic block
  53   builder.CreateRet(Add);
  54
  55   return ThreadSafeModule(std::move(M), std::move(Context));
  56 }
  57
  58 int main(int argc, char *argv[]) {
  59   // Initialize LLVM.
  60   InitLLVM X(argc, argv);
  61
  62   InitializeNativeTarget();
  63   InitializeNativeTargetAsmPrinter();
  64
  65   cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");
  66   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
  67
  68   // Create an LLJIT instance.
  69   auto J = ExitOnErr(LLJITBuilder().create());
  70   auto M = createDemoModule();
  71
  72   ExitOnErr(J->addIRModule(std::move(M)));
  73
  74   // Look up the JIT'd function, cast it to a function pointer, then call it.
  75   auto Add1Sym = ExitOnErr(J->lookup("add1"));
  76   int (*Add1)(int) = (int (*)(int))Add1Sym.getAddress();
  77
  78   int Result = Add1(42);
  79   outs() << "add1(42) = " << Result << "\n";
  80
  81   return 0;
  82 }