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189 lines
5.5 KiB
C++
189 lines
5.5 KiB
C++
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//===--- fibonacci.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 small program provides an example of how to build quickly a small
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// module with function Fibonacci and execute it with the JIT.
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//
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// This simple example shows as well 30% speed up with LLVM 1.3
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// in comparison to gcc 3.3.3 at AMD Athlon XP 1500+ .
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//
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// (Modified from HowToUseJIT.cpp and Stacker/lib/compiler/StackerCompiler.cpp)
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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 one function as follow:
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//
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// int fib(int x) {
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// if(x<=2) return 1;
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// return fib(x-1)+fib(x-2);
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// }
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//
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// then compile the module via JIT, then execute the `fib'
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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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#include <iostream>
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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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#include <llvm/Analysis/Verifier.h>
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#include "llvm/ExecutionEngine/ExecutionEngine.h"
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#include "llvm/ExecutionEngine/GenericValue.h"
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using namespace llvm;
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int main(int argc, char**argv) {
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int n = argc > 1 ? atol(argv[1]) : 44;
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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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// We are about to create the "fib" function:
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Function *FibF;
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{
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// first create type for the single argument of fib 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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// now create full type of the "fib" function:
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FunctionType *FibT = FunctionType::get(Type::IntTy, // type of result
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ArgT,
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/*not vararg*/false);
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// Now create the fib 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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FibF = new Function(FibT,
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Function::ExternalLinkage, // maybe too much
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"fib", M);
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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 fib function", FibF);
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// Get pointers to the constants ...
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Value *One = ConstantSInt::get(Type::IntTy, 1);
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Value *Two = ConstantSInt::get(Type::IntTy, 2);
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// Get pointers to the integer argument of the add1 function...
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assert(FibF->abegin() != FibF->aend()); // Make sure there's an arg
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Argument &ArgX = FibF->afront(); // Get the arg
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ArgX.setName("AnArg"); // Give it a nice symbolic name for fun.
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SetCondInst* CondInst
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= new SetCondInst( Instruction::SetLE,
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&ArgX, Two );
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BB->getInstList().push_back(CondInst);
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// Create the true_block
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BasicBlock* true_bb = new BasicBlock("arg<=2");
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// Create the return instruction and add it
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// to the basic block for true case:
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true_bb->getInstList().push_back(new ReturnInst(One));
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// Create an exit block
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BasicBlock* exit_bb = new BasicBlock("arg>2");
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{
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// create fib(x-1)
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CallInst* CallFibX1;
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{
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// Create the sub instruction... does not insert...
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Instruction *Sub
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= BinaryOperator::create(Instruction::Sub, &ArgX, One,
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"arg");
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exit_bb->getInstList().push_back(Sub);
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CallFibX1 = new CallInst(FibF, Sub, "fib(x-1)");
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exit_bb->getInstList().push_back(CallFibX1);
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}
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// create fib(x-2)
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CallInst* CallFibX2;
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{
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// Create the sub instruction... does not insert...
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Instruction * Sub
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= BinaryOperator::create(Instruction::Sub, &ArgX, Two,
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"arg");
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exit_bb->getInstList().push_back(Sub);
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CallFibX2 = new CallInst(FibF, Sub, "fib(x-2)");
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exit_bb->getInstList().push_back(CallFibX2);
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}
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// Create the add instruction... does not insert...
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Instruction *Add =
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BinaryOperator::create(Instruction::Add,
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CallFibX1, CallFibX2, "addresult");
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// explicitly insert it into the basic block...
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exit_bb->getInstList().push_back(Add);
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// Create the return instruction and add it to the basic block
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exit_bb->getInstList().push_back(new ReturnInst(Add));
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}
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// Create a branch on the SetCond
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BranchInst* br_inst =
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new BranchInst( true_bb, exit_bb, CondInst );
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BB->getInstList().push_back( br_inst );
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FibF->getBasicBlockList().push_back(true_bb);
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FibF->getBasicBlockList().push_back(exit_bb);
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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, false );
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// Call the `foo' function with argument n:
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std::vector<GenericValue> args(1);
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args[0].IntVal = n;
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std::clog << "verifying... ";
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if (verifyModule(*M)) {
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std::cerr << argv[0]
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<< ": assembly parsed, but does not verify as correct!\n";
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return 1;
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}
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else
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std::clog << "OK\n";
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std::clog << "We just constructed this LLVM module:\n\n---------\n" << *M;
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std::clog << "---------\nstarting fibonacci("
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<< n << ") with JIT...\n" << std::flush;
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GenericValue gv = EE->runFunction(FibF, args);
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// import result of execution:
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std::cout << "Result: " << gv.IntVal << std:: endl;
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return 0;
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}
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