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+//===--- HowToUseJIT.cpp - An example use of the JIT ----------------------===//
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+//
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+// The LLVM Compiler Infrastructure
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+//
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+// This file was developed by Valery A. Khamenya and is distributed under the
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+// University of Illinois Open Source License. See LICENSE.TXT for details.
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+//
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+//===----------------------------------------------------------------------===//
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+//
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+// This tool provides a single point of access to the LLVM compilation tools.
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+// It has many options. To discover the options supported please refer to the
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+// tools' manual page (docs/CommandGuide/html/llvmc.html) or run the tool with
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+// the --help option.
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+//
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+//===------------------------------------------------------------------------===
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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 two functions 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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+//
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+// int foo() {
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+// return add1(10);
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+// }
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+//
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+// then compile the module via JIT, then execute the `foo'
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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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+// Some remarks and questions:
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+//
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+// - could we invoke some code using noname functions too?
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+// e.g. evaluate "foo()+foo()" without fears to introduce
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+// conflict of temporary function name with some real
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+// existing function name?
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+//
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+
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+#include <iostream>
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+
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+#include <llvm/Module.h>
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+#include <llvm/DerivedTypes.h>
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+#include <llvm/Constants.h>
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+#include <llvm/Instructions.h>
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+#include <llvm/ModuleProvider.h>
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+
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+#include "llvm/ExecutionEngine/ExecutionEngine.h"
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+#include "llvm/ExecutionEngine/GenericValue.h"
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+
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+
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+using namespace llvm;
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+
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+int main() {
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+
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+ // Create some module to put our function into it.
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+ Module *M = new Module("test");
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+
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+
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+ // We are about to create the add1 function:
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+ Function *Add1F;
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+
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+ {
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+ // first create type for the single argument of add1 function:
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+ // the type is 'int ()'
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+ std::vector<const Type*> ArgT(1);
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+ ArgT[0] = Type::IntTy;
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+
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+ // now create full type of the add1 function:
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+ FunctionType *Add1T = FunctionType::get(Type::IntTy, // type of result
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+ ArgT,
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+ /*not vararg*/false);
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+
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+ // Now create the add1 function entry and
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+ // insert this entry into module M
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+ // (By passing a module as the last parameter to the Function constructor,
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+ // it automatically gets appended to the Module.)
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+ Add1F = new Function(Add1T,
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+ Function::ExternalLinkage, // maybe too much
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+ "add1", M);
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+
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+ // Add a basic block to the function... (again, it automatically inserts
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+ // because of the last argument.)
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+ BasicBlock *BB = new BasicBlock("EntryBlock of add1 function", Add1F);
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+
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+ // Get pointers to the constant `1'...
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+ Value *One = ConstantSInt::get(Type::IntTy, 1);
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+
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+ // Get pointers to the integer argument of the add1 function...
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+ assert(Add1F->abegin() != Add1F->aend()); // Make sure there's an arg
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+ Argument &ArgX = Add1F->afront(); // Get the arg
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+
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+ // Create the add instruction... does not insert...
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+ Instruction *Add = BinaryOperator::create(Instruction::Add, One, &ArgX,
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+ "addresult");
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+
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+ // explicitly insert it into the basic block...
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+ BB->getInstList().push_back(Add);
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+
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+ // Create the return instruction and add it to the basic block
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+ BB->getInstList().push_back(new ReturnInst(Add));
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+
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+ // function add1 is ready
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+ }
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+
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+
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+ // now we going to create function `foo':
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+ Function *FooF;
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+
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+ {
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+ // Create the foo function type:
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+ FunctionType *FooT =
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+ FunctionType::get(Type::IntTy, // result has type: 'int ()'
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+ std::vector<const Type*>(), // no arguments
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+ /*not vararg*/false);
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+
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+ // create the entry for function `foo' and insert
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+ // this entry into module M:
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+ FooF =
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+ new Function(FooT,
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+ Function::ExternalLinkage, // too wide?
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+ "foo", M);
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+
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+ // Add a basic block to the FooF function...
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+ BasicBlock *BB = new BasicBlock("EntryBlock of add1 function", FooF);
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+
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+ // Get pointers to the constant `10'...
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+ Value *Ten = ConstantSInt::get(Type::IntTy, 10);
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+
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+ // Put the argument Ten on stack and make call:
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+ // ...
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+ std::vector<Value*> Params;
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+ Params.push_back(Ten);
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+ CallInst * Add1CallRes = new CallInst(Add1F, Params, "add1", BB);
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+
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+ // Create the return instruction and add it to the basic block
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+ BB->getInstList().push_back(new ReturnInst(Add1CallRes));
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+
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+ }
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+
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+ // Now we going to create JIT ??
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+ ExistingModuleProvider* MP = new ExistingModuleProvider(M);
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+ ExecutionEngine* EE = ExecutionEngine::create( MP, true );
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+
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+ // Call the `foo' function with no arguments:
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+ std::vector<GenericValue> noargs;
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+ GenericValue gv = EE->runFunction(FooF, noargs);
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+
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+ // import result of execution:
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+ std::cout << "Result: " << gv.IntVal << std:: endl;
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+
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+ return 0;
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+}
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