examples/BrainF/BrainFDriver.cpp

   1 //===-- BrainFDriver.cpp - BrainF compiler driver -------------------------===//
   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 program converts the BrainF language into LLVM assembly,
  10 // which it can then run using the JIT or output as BitCode.
  11 //
  12 // This implementation has a tape of 65536 bytes,
  13 // with the head starting in the middle.
  14 // Range checking is off by default, so be careful.
  15 // It can be enabled with -abc.
  16 //
  17 // Use:
  18 // ./BrainF -jit      prog.bf          #Run program now
  19 // ./BrainF -jit -abc prog.bf          #Run program now safely
  20 // ./BrainF           prog.bf          #Write as BitCode
  21 //
  22 // lli prog.bf.bc                      #Run generated BitCode
  23 //
  24 //===----------------------------------------------------------------------===//
  25
  26 #include "BrainF.h"
  27 #include "llvm/ADT/APInt.h"
  28 #include "llvm/Bitcode/BitcodeWriter.h"
  29 #include "llvm/ExecutionEngine/ExecutionEngine.h"
  30 #include "llvm/ExecutionEngine/GenericValue.h"
  31 #include "llvm/ExecutionEngine/MCJIT.h"
  32 #include "llvm/IR/BasicBlock.h"
  33 #include "llvm/IR/Constants.h"
  34 #include "llvm/IR/DerivedTypes.h"
  35 #include "llvm/IR/Function.h"
  36 #include "llvm/IR/Instructions.h"
  37 #include "llvm/IR/LLVMContext.h"
  38 #include "llvm/IR/Module.h"
  39 #include "llvm/IR/Value.h"
  40 #include "llvm/IR/Verifier.h"
  41 #include "llvm/Support/Casting.h"
  42 #include "llvm/Support/CommandLine.h"
  43 #include "llvm/Support/FileSystem.h"
  44 #include "llvm/Support/ManagedStatic.h"
  45 #include "llvm/Support/TargetSelect.h"
  46 #include "llvm/Support/raw_ostream.h"
  47 #include <algorithm>
  48 #include <cstdlib>
  49 #include <fstream>
  50 #include <iostream>
  51 #include <memory>
  52 #include <string>
  53 #include <system_error>
  54 #include <vector>
  55
  56 using namespace llvm;
  57
  58 //Command line options
  59
  60 static cl::opt<std::string>
  61 InputFilename(cl::Positional, cl::desc("<input brainf>"));
  62
  63 static cl::opt<std::string>
  64 OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"));
  65
  66 static cl::opt<bool>
  67 ArrayBoundsChecking("abc", cl::desc("Enable array bounds checking"));
  68
  69 static cl::opt<bool>
  70 JIT("jit", cl::desc("Run program Just-In-Time"));
  71
  72 //Add main function so can be fully compiled
  73 void addMainFunction(Module *mod) {
  74   //define i32 @main(i32 %argc, i8 **%argv)
  75   FunctionType *main_func_fty = FunctionType::get(
  76       Type::getInt32Ty(mod->getContext()),
  77       {Type::getInt32Ty(mod->getContext()),
  78        Type::getInt8Ty(mod->getContext())->getPointerTo()->getPointerTo()},
  79       false);
  80   Function *main_func =
  81       Function::Create(main_func_fty, Function::ExternalLinkage, "main", mod);
  82
  83   {
  84     Function::arg_iterator args = main_func->arg_begin();
  85     Value *arg_0 = &*args++;
  86     arg_0->setName("argc");
  87     Value *arg_1 = &*args++;
  88     arg_1->setName("argv");
  89   }
  90
  91   //main.0:
  92   BasicBlock *bb = BasicBlock::Create(mod->getContext(), "main.0", main_func);
  93
  94   //call void @brainf()
  95   {
  96     CallInst *brainf_call = CallInst::Create(mod->getFunction("brainf"),
  97                                              "", bb);
  98     brainf_call->setTailCall(false);
  99   }
 100
 101   //ret i32 0
 102   ReturnInst::Create(mod->getContext(),
 103                      ConstantInt::get(mod->getContext(), APInt(32, 0)), bb);
 104 }
 105
 106 int main(int argc, char **argv) {
 107   cl::ParseCommandLineOptions(argc, argv, " BrainF compiler\n");
 108
 109   LLVMContext Context;
 110
 111   if (InputFilename == "") {
 112     errs() << "Error: You must specify the filename of the program to "
 113     "be compiled.  Use --help to see the options.\n";
 114     abort();
 115   }
 116
 117   //Get the output stream
 118   raw_ostream *out = &outs();
 119   if (!JIT) {
 120     if (OutputFilename == "") {
 121       std::string base = InputFilename;
 122       if (InputFilename == "-") { base = "a"; }
 123
 124       // Use default filename.
 125       OutputFilename = base+".bc";
 126     }
 127     if (OutputFilename != "-") {
 128       std::error_code EC;
 129       out = new raw_fd_ostream(OutputFilename, EC, sys::fs::OF_None);
 130     }
 131   }
 132
 133   //Get the input stream
 134   std::istream *in = &std::cin;
 135   if (InputFilename != "-")
 136     in = new std::ifstream(InputFilename.c_str());
 137
 138   //Gather the compile flags
 139   BrainF::CompileFlags cf = BrainF::flag_off;
 140   if (ArrayBoundsChecking)
 141     cf = BrainF::CompileFlags(cf | BrainF::flag_arraybounds);
 142
 143   //Read the BrainF program
 144   BrainF bf;
 145   std::unique_ptr<Module> Mod(bf.parse(in, 65536, cf, Context)); // 64 KiB
 146   if (in != &std::cin)
 147     delete in;
 148   addMainFunction(Mod.get());
 149
 150   //Verify generated code
 151   if (verifyModule(*Mod)) {
 152     errs() << "Error: module failed verification.  This shouldn't happen.\n";
 153     abort();
 154   }
 155
 156   //Write it out
 157   if (JIT) {
 158     InitializeNativeTarget();
 159     InitializeNativeTargetAsmPrinter();
 160
 161     outs() << "------- Running JIT -------\n";
 162     Module &M = *Mod;
 163     ExecutionEngine *ee = EngineBuilder(std::move(Mod)).create();
 164     if (!ee) {
 165       errs() << "Error: execution engine creation failed.\n";
 166       abort();
 167     }
 168     std::vector<GenericValue> args;
 169     Function *brainf_func = M.getFunction("brainf");
 170     GenericValue gv = ee->runFunction(brainf_func, args);
 171     // Genereated code calls putchar, and output is not guaranteed without fflush.
 172     // The better place for fflush(stdout) call would be the generated code, but it
 173     // is unmanageable because stdout linkage name depends on stdlib implementation.
 174     fflush(stdout);
 175   } else {
 176     WriteBitcodeToFile(*Mod, *out);
 177   }
 178
 179   //Clean up
 180   if (out != &outs())
 181     delete out;
 182
 183   llvm_shutdown();
 184
 185   return 0;
 186 }