Imported Upstream version 5.18.0.161

Former-commit-id: 4db48158d3a35497b8f118ab21b5f08ac3d86d98

external/llvm/examples/HowToUseJIT/HowToUseJIT.cpp

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+//===-- examples/HowToUseJIT/HowToUseJIT.cpp - An example use of the JIT --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This small program provides an example of how to quickly build a small
+//  module with two functions and execute it with the JIT.
+//
+// Goal:
+//  The goal of this snippet is to create in the memory
+//  the LLVM module consisting of two functions as follow: 
+//
+// int add1(int x) {
+//   return x+1;
+// }
+//
+// int foo() {
+//   return add1(10);
+// }
+//
+// then compile the module via JIT, then execute the `foo'
+// function and return result to a driver, i.e. to a "host program".
+//
+// Some remarks and questions:
+//
+// - could we invoke some code using noname functions too?
+//   e.g. evaluate "foo()+foo()" without fears to introduce
+//   conflict of temporary function name with some real
+//   existing function name?
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/IR/Argument.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/ManagedStatic.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <memory>
+#include <vector>
+
+using namespace llvm;
+
+int main() {
+  InitializeNativeTarget();
+
+  LLVMContext Context;
+  
+  // Create some module to put our function into it.
+  std::unique_ptr<Module> Owner = make_unique<Module>("test", Context);
+  Module *M = Owner.get();
+
+  // Create the add1 function entry and insert this entry into module M.  The
+  // function will have a return type of "int" and take an argument of "int".
+  Function *Add1F =
+    cast<Function>(M->getOrInsertFunction("add1", Type::getInt32Ty(Context),
+                                          Type::getInt32Ty(Context)));
+
+  // Add a basic block to the function. As before, it automatically inserts
+  // because of the last argument.
+  BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", Add1F);
+
+  // Create a basic block builder with default parameters.  The builder will
+  // automatically append instructions to the basic block `BB'.
+  IRBuilder<> builder(BB);
+
+  // Get pointers to the constant `1'.
+  Value *One = builder.getInt32(1);
+
+  // Get pointers to the integer argument of the add1 function...
+  assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
+  Argument *ArgX = &*Add1F->arg_begin();          // Get the arg
+  ArgX->setName("AnArg");            // Give it a nice symbolic name for fun.
+
+  // Create the add instruction, inserting it into the end of BB.
+  Value *Add = builder.CreateAdd(One, ArgX);
+
+  // Create the return instruction and add it to the basic block
+  builder.CreateRet(Add);
+
+  // Now, function add1 is ready.
+
+  // Now we're going to create function `foo', which returns an int and takes no
+  // arguments.
+  Function *FooF =
+    cast<Function>(M->getOrInsertFunction("foo", Type::getInt32Ty(Context)));
+
+  // Add a basic block to the FooF function.
+  BB = BasicBlock::Create(Context, "EntryBlock", FooF);
+
+  // Tell the basic block builder to attach itself to the new basic block
+  builder.SetInsertPoint(BB);
+
+  // Get pointer to the constant `10'.
+  Value *Ten = builder.getInt32(10);
+
+  // Pass Ten to the call to Add1F
+  CallInst *Add1CallRes = builder.CreateCall(Add1F, Ten);
+  Add1CallRes->setTailCall(true);
+
+  // Create the return instruction and add it to the basic block.
+  builder.CreateRet(Add1CallRes);
+
+  // Now we create the JIT.
+  ExecutionEngine* EE = EngineBuilder(std::move(Owner)).create();
+
+  outs() << "We just constructed this LLVM module:\n\n" << *M;
+  outs() << "\n\nRunning foo: ";
+  outs().flush();
+
+  // Call the `foo' function with no arguments:
+  std::vector<GenericValue> noargs;
+  GenericValue gv = EE->runFunction(FooF, noargs);
+
+  // Import result of execution:
+  outs() << "Result: " << gv.IntVal << "\n";
+  delete EE;
+  llvm_shutdown();
+  return 0;
+}