llvm/examples/HowToUseJIT/HowToUseJIT.cpp
Chris Lattner 944fac71e0 Switch the asmprinter (.ll) and all the stuff it requires over to
use raw_ostream instead of std::ostream.  Among other goodness,
this speeds up llvm-dis of kc++ with a release build from 0.85s
to 0.49s (88% faster).

Other interesting changes:
 1) This makes Value::print be non-virtual.
 2) AP[S]Int and ConstantRange can no longer print to ostream directly, 
    use raw_ostream instead.
 3) This fixes a bug in raw_os_ostream where it didn't flush itself 
    when destroyed.
 4) This adds a new SDNode::print method, instead of only allowing "dump".


A lot of APIs have both std::ostream and raw_ostream versions, it would
be useful to go through and systematically anihilate the std::ostream 
versions.

This passes dejagnu, but there may be minor fallout, plz let me know if
so and I'll fix it.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55263 91177308-0d34-0410-b5e6-96231b3b80d8
2008-08-23 22:23:09 +00:00

114 lines
3.8 KiB
C++

//===-- 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/Module.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/ModuleProvider.h"
#include "llvm/ExecutionEngine/JIT.h"
#include "llvm/ExecutionEngine/Interpreter.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
int main() {
// Create some module to put our function into it.
Module *M = new Module("test");
// 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".
// The '0' terminates the list of argument types.
Function *Add1F =
cast<Function>(M->getOrInsertFunction("add1", Type::Int32Ty, Type::Int32Ty,
(Type *)0));
// Add a basic block to the function. As before, it automatically inserts
// because of the last argument.
BasicBlock *BB = BasicBlock::Create("EntryBlock", Add1F);
// Get pointers to the constant `1'.
Value *One = ConstantInt::get(Type::Int32Ty, 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.
Instruction *Add = BinaryOperator::CreateAdd(One, ArgX, "addresult", BB);
// Create the return instruction and add it to the basic block
ReturnInst::Create(Add, BB);
// Now, function add1 is ready.
// Now we going to create function `foo', which returns an int and takes no
// arguments.
Function *FooF =
cast<Function>(M->getOrInsertFunction("foo", Type::Int32Ty, (Type *)0));
// Add a basic block to the FooF function.
BB = BasicBlock::Create("EntryBlock", FooF);
// Get pointers to the constant `10'.
Value *Ten = ConstantInt::get(Type::Int32Ty, 10);
// Pass Ten to the call call:
CallInst *Add1CallRes = CallInst::Create(Add1F, Ten, "add1", BB);
Add1CallRes->setTailCall(true);
// Create the return instruction and add it to the basic block.
ReturnInst::Create(Add1CallRes, BB);
// Now we create the JIT.
ExistingModuleProvider* MP = new ExistingModuleProvider(M);
ExecutionEngine* EE = ExecutionEngine::create(MP, false);
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";
return 0;
}