llvm/examples/HowToUseLLJIT/HowToUseLLJIT.cpp

   1 //===------- HowToUseLLJIT.cpp - An example use of ORC-based LLJIT --------===//
   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 //  This small program provides an example of how to quickly build a small
  10 //  module with a 'add1' function and use of IRBuilder to create add & return
  11 //  instructions.
  12 //
  13 // Goal:
  14 //  The goal of this snippet is to create in the memory
  15 //  the LLVM module consisting of a function as follow:
  16 //
  17 // int add1(int x) {
  18 //   return x+1;
  19 // }
  20 //  add1(42);
  21 //
  22 // then compile the module via LLJIT, then execute the 'add1'
  23 // function and return result to a driver, i.e. to a "host program".
  24 //
  25 //===----------------------------------------------------------------------===//
  26
  27 #include "llvm/ExecutionEngine/Orc/LLJIT.h"
  28 #include "llvm/IR/Function.h"
  29 #include "llvm/IR/IRBuilder.h"
  30 #include "llvm/IR/Module.h"
  31 #include "llvm/Support/CommandLine.h"
  32 #include "llvm/Support/InitLLVM.h"
  33 #include "llvm/Support/TargetSelect.h"
  34 #include "llvm/Support/raw_ostream.h"
  35
  36 using namespace llvm;
  37 using namespace llvm::orc;
  38
  39 ExitOnError ExitOnErr;
  40
  41 ThreadSafeModule createDemoModule() {
  42   auto Context = std::make_unique<LLVMContext>();
  43   auto M = std::make_unique<Module>("test", *Context);
  44
  45   // Create the add1 function entry and insert this entry into module M.  The
  46   // function will have a return type of "int" and take an argument of "int".
  47   Function *Add1F =
  48       Function::Create(FunctionType::get(Type::getInt32Ty(*Context),
  49                                          {Type::getInt32Ty(*Context)}, false),
  50                        Function::ExternalLinkage, "add1", M.get());
  51
  52   // Add a basic block to the function. As before, it automatically inserts
  53   // because of the last argument.
  54   BasicBlock *BB = BasicBlock::Create(*Context, "EntryBlock", Add1F);
  55
  56   // Create a basic block builder with default parameters.  The builder will
  57   // automatically append instructions to the basic block `BB'.
  58   IRBuilder<> builder(BB);
  59
  60   // Get pointers to the constant `1'.
  61   Value *One = builder.getInt32(1);
  62
  63   // Get pointers to the integer argument of the add1 function...
  64   assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
  65   Argument *ArgX = &*Add1F->arg_begin();          // Get the arg
  66   ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.
  67
  68   // Create the add instruction, inserting it into the end of BB.
  69   Value *Add = builder.CreateAdd(One, ArgX);
  70
  71   // Create the return instruction and add it to the basic block
  72   builder.CreateRet(Add);
  73
  74   return ThreadSafeModule(std::move(M), std::move(Context));
  75 }
  76
  77 int main(int argc, char *argv[]) {
  78   // Initialize LLVM.
  79   InitLLVM X(argc, argv);
  80
  81   InitializeNativeTarget();
  82   InitializeNativeTargetAsmPrinter();
  83
  84   cl::ParseCommandLineOptions(argc, argv, "HowToUseLLJIT");
  85   ExitOnErr.setBanner(std::string(argv[0]) + ": ");
  86
  87   // Create an LLJIT instance.
  88   auto J = ExitOnErr(LLJITBuilder().create());
  89   auto M = createDemoModule();
  90
  91   ExitOnErr(J->addIRModule(std::move(M)));
  92
  93   // Look up the JIT'd function, cast it to a function pointer, then call it.
  94   auto Add1Addr = ExitOnErr(J->lookup("add1"));
  95   int (*Add1)(int) = Add1Addr.toPtr<int(int)>();
  96
  97   int Result = Add1(42);
  98   outs() << "add1(42) = " << Result << "\n";
  99
 100   return 0;
 101 }