examples/BrainF/BrainF.cpp

   1 //===-- BrainF.cpp - BrainF compiler example ----------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===--------------------------------------------------------------------===//
   9 //
  10 // This class compiles the BrainF language into LLVM assembly.
  11 //
  12 // The BrainF language has 8 commands:
  13 // Command   Equivalent C    Action
  14 // -------   ------------    ------
  15 // ,         *h=getchar();   Read a character from stdin, 255 on EOF
  16 // .         putchar(*h);    Write a character to stdout
  17 // -         --*h;           Decrement tape
  18 // +         ++*h;           Increment tape
  19 // <         --h;            Move head left
  20 // >         ++h;            Move head right
  21 // [         while(*h) {     Start loop
  22 // ]         }               End loop
  23 //
  24 //===--------------------------------------------------------------------===//
  25
  26 #include "BrainF.h"
  27 #include "llvm/Constants.h"
  28 #include "llvm/Instructions.h"
  29 #include "llvm/Intrinsics.h"
  30 #include "llvm/ADT/STLExtras.h"
  31 #include <iostream>
  32 using namespace llvm;
  33
  34 //Set the constants for naming
  35 const char *BrainF::tapereg = "tape";
  36 const char *BrainF::headreg = "head";
  37 const char *BrainF::label   = "brainf";
  38 const char *BrainF::testreg = "test";
  39
  40 Module *BrainF::parse(std::istream *in1, int mem, CompileFlags cf,
  41                       LLVMContext& Context) {
  42   in       = in1;
  43   memtotal = mem;
  44   comflag  = cf;
  45
  46   header(Context);
  47   readloop(0, 0, 0, Context);
  48   delete builder;
  49   return module;
  50 }
  51
  52 void BrainF::header(LLVMContext& C) {
  53   module = new Module("BrainF", C);
  54
  55   //Function prototypes
  56
  57   //declare void @llvm.memset.p0i8.i32(i8 *, i8, i32, i32, i1)
  58   Type *Tys[] = { Type::getInt8PtrTy(C), Type::getInt32Ty(C) };
  59   Function *memset_func = Intrinsic::getDeclaration(module, Intrinsic::memset,
  60                                                     Tys);
  61
  62   //declare i32 @getchar()
  63   getchar_func = cast<Function>(module->
  64     getOrInsertFunction("getchar", IntegerType::getInt32Ty(C), NULL));
  65
  66   //declare i32 @putchar(i32)
  67   putchar_func = cast<Function>(module->
  68     getOrInsertFunction("putchar", IntegerType::getInt32Ty(C),
  69                         IntegerType::getInt32Ty(C), NULL));
  70
  71
  72   //Function header
  73
  74   //define void @brainf()
  75   brainf_func = cast<Function>(module->
  76     getOrInsertFunction("brainf", Type::getVoidTy(C), NULL));
  77
  78   builder = new IRBuilder<>(BasicBlock::Create(C, label, brainf_func));
  79
  80   //%arr = malloc i8, i32 %d
  81   ConstantInt *val_mem = ConstantInt::get(C, APInt(32, memtotal));
  82   BasicBlock* BB = builder->GetInsertBlock();
  83   Type* IntPtrTy = IntegerType::getInt32Ty(C);
  84   Type* Int8Ty = IntegerType::getInt8Ty(C);
  85   Constant* allocsize = ConstantExpr::getSizeOf(Int8Ty);
  86   allocsize = ConstantExpr::getTruncOrBitCast(allocsize, IntPtrTy);
  87   ptr_arr = CallInst::CreateMalloc(BB, IntPtrTy, Int8Ty, allocsize, val_mem,
  88                                    NULL, "arr");
  89   BB->getInstList().push_back(cast<Instruction>(ptr_arr));
  90
  91   //call void @llvm.memset.p0i8.i32(i8 *%arr, i8 0, i32 %d, i32 1, i1 0)
  92   {
  93     Value *memset_params[] = {
  94       ptr_arr,
  95       ConstantInt::get(C, APInt(8, 0)),
  96       val_mem,
  97       ConstantInt::get(C, APInt(32, 1)),
  98       ConstantInt::get(C, APInt(1, 0))
  99     };
 100
 101     CallInst *memset_call = builder->
 102       CreateCall(memset_func, memset_params);
 103     memset_call->setTailCall(false);
 104   }
 105
 106   //%arrmax = getelementptr i8 *%arr, i32 %d
 107   if (comflag & flag_arraybounds) {
 108     ptr_arrmax = builder->
 109       CreateGEP(ptr_arr, ConstantInt::get(C, APInt(32, memtotal)), "arrmax");
 110   }
 111
 112   //%head.%d = getelementptr i8 *%arr, i32 %d
 113   curhead = builder->CreateGEP(ptr_arr,
 114                                ConstantInt::get(C, APInt(32, memtotal/2)),
 115                                headreg);
 116
 117
 118
 119   //Function footer
 120
 121   //brainf.end:
 122   endbb = BasicBlock::Create(C, label, brainf_func);
 123
 124   //call free(i8 *%arr)
 125   endbb->getInstList().push_back(CallInst::CreateFree(ptr_arr, endbb));
 126
 127   //ret void
 128   ReturnInst::Create(C, endbb);
 129
 130
 131
 132   //Error block for array out of bounds
 133   if (comflag & flag_arraybounds)
 134   {
 135     //@aberrormsg = internal constant [%d x i8] c"\00"
 136     Constant *msg_0 =
 137       ConstantArray::get(C, "Error: The head has left the tape.", true);
 138
 139     GlobalVariable *aberrormsg = new GlobalVariable(
 140       *module,
 141       msg_0->getType(),
 142       true,
 143       GlobalValue::InternalLinkage,
 144       msg_0,
 145       "aberrormsg");
 146
 147     //declare i32 @puts(i8 *)
 148     Function *puts_func = cast<Function>(module->
 149       getOrInsertFunction("puts", IntegerType::getInt32Ty(C),
 150                       PointerType::getUnqual(IntegerType::getInt8Ty(C)), NULL));
 151
 152     //brainf.aberror:
 153     aberrorbb = BasicBlock::Create(C, label, brainf_func);
 154
 155     //call i32 @puts(i8 *getelementptr([%d x i8] *@aberrormsg, i32 0, i32 0))
 156     {
 157       Constant *zero_32 = Constant::getNullValue(IntegerType::getInt32Ty(C));
 158
 159       Constant *gep_params[] = {
 160         zero_32,
 161         zero_32
 162       };
 163
 164       Constant *msgptr = ConstantExpr::
 165         getGetElementPtr(aberrormsg, gep_params);
 166
 167       Value *puts_params[] = {
 168         msgptr
 169       };
 170
 171       CallInst *puts_call =
 172         CallInst::Create(puts_func,
 173                          puts_params,
 174                          "", aberrorbb);
 175       puts_call->setTailCall(false);
 176     }
 177
 178     //br label %brainf.end
 179     BranchInst::Create(endbb, aberrorbb);
 180   }
 181 }
 182
 183 void BrainF::readloop(PHINode *phi, BasicBlock *oldbb, BasicBlock *testbb,
 184                       LLVMContext &C) {
 185   Symbol cursym = SYM_NONE;
 186   int curvalue = 0;
 187   Symbol nextsym = SYM_NONE;
 188   int nextvalue = 0;
 189   char c;
 190   int loop;
 191   int direction;
 192
 193   while(cursym != SYM_EOF && cursym != SYM_ENDLOOP) {
 194     // Write out commands
 195     switch(cursym) {
 196       case SYM_NONE:
 197         // Do nothing
 198         break;
 199
 200       case SYM_READ:
 201         {
 202           //%tape.%d = call i32 @getchar()
 203           CallInst *getchar_call = builder->CreateCall(getchar_func, tapereg);
 204           getchar_call->setTailCall(false);
 205           Value *tape_0 = getchar_call;
 206
 207           //%tape.%d = trunc i32 %tape.%d to i8
 208           Value *tape_1 = builder->
 209             CreateTrunc(tape_0, IntegerType::getInt8Ty(C), tapereg);
 210
 211           //store i8 %tape.%d, i8 *%head.%d
 212           builder->CreateStore(tape_1, curhead);
 213         }
 214         break;
 215
 216       case SYM_WRITE:
 217         {
 218           //%tape.%d = load i8 *%head.%d
 219           LoadInst *tape_0 = builder->CreateLoad(curhead, tapereg);
 220
 221           //%tape.%d = sext i8 %tape.%d to i32
 222           Value *tape_1 = builder->
 223             CreateSExt(tape_0, IntegerType::getInt32Ty(C), tapereg);
 224
 225           //call i32 @putchar(i32 %tape.%d)
 226           Value *putchar_params[] = {
 227             tape_1
 228           };
 229           CallInst *putchar_call = builder->
 230             CreateCall(putchar_func,
 231                        putchar_params);
 232           putchar_call->setTailCall(false);
 233         }
 234         break;
 235
 236       case SYM_MOVE:
 237         {
 238           //%head.%d = getelementptr i8 *%head.%d, i32 %d
 239           curhead = builder->
 240             CreateGEP(curhead, ConstantInt::get(C, APInt(32, curvalue)),
 241                       headreg);
 242
 243           //Error block for array out of bounds
 244           if (comflag & flag_arraybounds)
 245           {
 246             //%test.%d = icmp uge i8 *%head.%d, %arrmax
 247             Value *test_0 = builder->
 248               CreateICmpUGE(curhead, ptr_arrmax, testreg);
 249
 250             //%test.%d = icmp ult i8 *%head.%d, %arr
 251             Value *test_1 = builder->
 252               CreateICmpULT(curhead, ptr_arr, testreg);
 253
 254             //%test.%d = or i1 %test.%d, %test.%d
 255             Value *test_2 = builder->
 256               CreateOr(test_0, test_1, testreg);
 257
 258             //br i1 %test.%d, label %main.%d, label %main.%d
 259             BasicBlock *nextbb = BasicBlock::Create(C, label, brainf_func);
 260             builder->CreateCondBr(test_2, aberrorbb, nextbb);
 261
 262             //main.%d:
 263             builder->SetInsertPoint(nextbb);
 264           }
 265         }
 266         break;
 267
 268       case SYM_CHANGE:
 269         {
 270           //%tape.%d = load i8 *%head.%d
 271           LoadInst *tape_0 = builder->CreateLoad(curhead, tapereg);
 272
 273           //%tape.%d = add i8 %tape.%d, %d
 274           Value *tape_1 = builder->
 275             CreateAdd(tape_0, ConstantInt::get(C, APInt(8, curvalue)), tapereg);
 276
 277           //store i8 %tape.%d, i8 *%head.%d\n"
 278           builder->CreateStore(tape_1, curhead);
 279         }
 280         break;
 281
 282       case SYM_LOOP:
 283         {
 284           //br label %main.%d
 285           BasicBlock *testbb = BasicBlock::Create(C, label, brainf_func);
 286           builder->CreateBr(testbb);
 287
 288           //main.%d:
 289           BasicBlock *bb_0 = builder->GetInsertBlock();
 290           BasicBlock *bb_1 = BasicBlock::Create(C, label, brainf_func);
 291           builder->SetInsertPoint(bb_1);
 292
 293           // Make part of PHI instruction now, wait until end of loop to finish
 294           PHINode *phi_0 =
 295             PHINode::Create(PointerType::getUnqual(IntegerType::getInt8Ty(C)),
 296                             2, headreg, testbb);
 297           phi_0->addIncoming(curhead, bb_0);
 298           curhead = phi_0;
 299
 300           readloop(phi_0, bb_1, testbb, C);
 301         }
 302         break;
 303
 304       default:
 305         std::cerr << "Error: Unknown symbol.\n";
 306         abort();
 307         break;
 308     }
 309
 310     cursym = nextsym;
 311     curvalue = nextvalue;
 312     nextsym = SYM_NONE;
 313
 314     // Reading stdin loop
 315     loop = (cursym == SYM_NONE)
 316         || (cursym == SYM_MOVE)
 317         || (cursym == SYM_CHANGE);
 318     while(loop) {
 319       *in>>c;
 320       if (in->eof()) {
 321         if (cursym == SYM_NONE) {
 322           cursym = SYM_EOF;
 323         } else {
 324           nextsym = SYM_EOF;
 325         }
 326         loop = 0;
 327       } else {
 328         direction = 1;
 329         switch(c) {
 330           case '-':
 331             direction = -1;
 332             // Fall through
 333
 334           case '+':
 335             if (cursym == SYM_CHANGE) {
 336               curvalue += direction;
 337               // loop = 1
 338             } else {
 339               if (cursym == SYM_NONE) {
 340                 cursym = SYM_CHANGE;
 341                 curvalue = direction;
 342                 // loop = 1
 343               } else {
 344                 nextsym = SYM_CHANGE;
 345                 nextvalue = direction;
 346                 loop = 0;
 347               }
 348             }
 349             break;
 350
 351           case '<':
 352             direction = -1;
 353             // Fall through
 354
 355           case '>':
 356             if (cursym == SYM_MOVE) {
 357               curvalue += direction;
 358               // loop = 1
 359             } else {
 360               if (cursym == SYM_NONE) {
 361                 cursym = SYM_MOVE;
 362                 curvalue = direction;
 363                 // loop = 1
 364               } else {
 365                 nextsym = SYM_MOVE;
 366                 nextvalue = direction;
 367                 loop = 0;
 368               }
 369             }
 370             break;
 371
 372           case ',':
 373             if (cursym == SYM_NONE) {
 374               cursym = SYM_READ;
 375             } else {
 376               nextsym = SYM_READ;
 377             }
 378             loop = 0;
 379             break;
 380
 381           case '.':
 382             if (cursym == SYM_NONE) {
 383               cursym = SYM_WRITE;
 384             } else {
 385               nextsym = SYM_WRITE;
 386             }
 387             loop = 0;
 388             break;
 389
 390           case '[':
 391             if (cursym == SYM_NONE) {
 392               cursym = SYM_LOOP;
 393             } else {
 394               nextsym = SYM_LOOP;
 395             }
 396             loop = 0;
 397             break;
 398
 399           case ']':
 400             if (cursym == SYM_NONE) {
 401               cursym = SYM_ENDLOOP;
 402             } else {
 403               nextsym = SYM_ENDLOOP;
 404             }
 405             loop = 0;
 406             break;
 407
 408           // Ignore other characters
 409           default:
 410             break;
 411         }
 412       }
 413     }
 414   }
 415
 416   if (cursym == SYM_ENDLOOP) {
 417     if (!phi) {
 418       std::cerr << "Error: Extra ']'\n";
 419       abort();
 420     }
 421
 422     // Write loop test
 423     {
 424       //br label %main.%d
 425       builder->CreateBr(testbb);
 426
 427       //main.%d:
 428
 429       //%head.%d = phi i8 *[%head.%d, %main.%d], [%head.%d, %main.%d]
 430       //Finish phi made at beginning of loop
 431       phi->addIncoming(curhead, builder->GetInsertBlock());
 432       Value *head_0 = phi;
 433
 434       //%tape.%d = load i8 *%head.%d
 435       LoadInst *tape_0 = new LoadInst(head_0, tapereg, testbb);
 436
 437       //%test.%d = icmp eq i8 %tape.%d, 0
 438       ICmpInst *test_0 = new ICmpInst(*testbb, ICmpInst::ICMP_EQ, tape_0,
 439                                     ConstantInt::get(C, APInt(8, 0)), testreg);
 440
 441       //br i1 %test.%d, label %main.%d, label %main.%d
 442       BasicBlock *bb_0 = BasicBlock::Create(C, label, brainf_func);
 443       BranchInst::Create(bb_0, oldbb, test_0, testbb);
 444
 445       //main.%d:
 446       builder->SetInsertPoint(bb_0);
 447
 448       //%head.%d = phi i8 *[%head.%d, %main.%d]
 449       PHINode *phi_1 = builder->
 450         CreatePHI(PointerType::getUnqual(IntegerType::getInt8Ty(C)), 1,
 451                   headreg);
 452       phi_1->addIncoming(head_0, testbb);
 453       curhead = phi_1;
 454     }
 455
 456     return;
 457   }
 458
 459   //End of the program, so go to return block
 460   builder->CreateBr(endbb);
 461
 462   if (phi) {
 463     std::cerr << "Error: Missing ']'\n";
 464     abort();
 465   }
 466 }