examples/BrainF/BrainF.cpp

   1 //===-- BrainF.cpp - BrainF compiler example ----------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file was developed by Sterling Stein and is distributed under the
   6 // University of Illinois Open Source 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/ADT/STLExtras.h"
  29
  30 using namespace llvm;
  31
  32 //Set the constants for naming
  33 const char *BrainF::tapereg = "tape";
  34 const char *BrainF::headreg = "head";
  35 const char *BrainF::label   = "brainf";
  36 const char *BrainF::testreg = "test";
  37
  38 Module *BrainF::parse(std::istream *in1, int mem, CompileFlags cf) {
  39   in       = in1;
  40   memtotal = mem;
  41   comflag  = cf;
  42
  43   header();
  44   readloop(0, 0, 0);
  45   delete builder;
  46   return module;
  47 }
  48
  49 void BrainF::header() {
  50   module = new Module("BrainF");
  51
  52   //Function prototypes
  53
  54   //declare void @llvm.memset.i32(i8 *, i8, i32, i32)
  55   Function *memset_func = cast<Function>(module->
  56     getOrInsertFunction("llvm.memset.i32", Type::VoidTy,
  57                         PointerType::getUnqual(IntegerType::Int8Ty),
  58                         IntegerType::Int8Ty, IntegerType::Int32Ty,
  59                         IntegerType::Int32Ty, NULL));
  60
  61   //declare i32 @getchar()
  62   getchar_func = cast<Function>(module->
  63     getOrInsertFunction("getchar", IntegerType::Int32Ty, NULL));
  64
  65   //declare i32 @putchar(i32)
  66   putchar_func = cast<Function>(module->
  67     getOrInsertFunction("putchar", IntegerType::Int32Ty,
  68                         IntegerType::Int32Ty, NULL));
  69
  70
  71   //Function header
  72
  73   //define void @brainf()
  74   brainf_func = cast<Function>(module->
  75     getOrInsertFunction("brainf", Type::VoidTy, NULL));
  76
  77   builder = new LLVMBuilder(new BasicBlock(label, brainf_func));
  78
  79   //%arr = malloc i8, i32 %d
  80   ConstantInt *val_mem = ConstantInt::get(APInt(32, memtotal));
  81   ptr_arr = builder->CreateMalloc(IntegerType::Int8Ty, val_mem, "arr");
  82
  83   //call void @llvm.memset.i32(i8 *%arr, i8 0, i32 %d, i32 1)
  84   {
  85     Value *memset_params[] = {
  86       ptr_arr,
  87       ConstantInt::get(APInt(8, 0)),
  88       val_mem,
  89       ConstantInt::get(APInt(32, 1))
  90     };
  91
  92     CallInst *memset_call = builder->
  93       CreateCall(memset_func, memset_params, array_endof(memset_params));
  94     memset_call->setTailCall(false);
  95   }
  96
  97   //%arrmax = getelementptr i8 *%arr, i32 %d
  98   if (comflag & flag_arraybounds) {
  99     ptr_arrmax = builder->
 100       CreateGEP(ptr_arr, ConstantInt::get(APInt(32, memtotal)), "arrmax");
 101   }
 102
 103   //%head.%d = getelementptr i8 *%arr, i32 %d
 104   curhead = builder->CreateGEP(ptr_arr,
 105                                ConstantInt::get(APInt(32, memtotal/2)),
 106                                headreg);
 107
 108
 109
 110   //Function footer
 111
 112   //brainf.end:
 113   endbb = new BasicBlock(label, brainf_func);
 114
 115   //free i8 *%arr
 116   new FreeInst(ptr_arr, endbb);
 117
 118   //ret void
 119   new ReturnInst(endbb);
 120
 121
 122
 123   //Error block for array out of bounds
 124   if (comflag & flag_arraybounds)
 125   {
 126     //@aberrormsg = internal constant [%d x i8] c"\00"
 127     Constant *msg_0 = ConstantArray::
 128       get("Error: The head has left the tape.", true);
 129
 130     GlobalVariable *aberrormsg = new GlobalVariable(
 131       msg_0->getType(),
 132       true,
 133       GlobalValue::InternalLinkage,
 134       msg_0,
 135       "aberrormsg",
 136       module);
 137
 138     //declare i32 @puts(i8 *)
 139     Function *puts_func = cast<Function>(module->
 140       getOrInsertFunction("puts", IntegerType::Int32Ty,
 141                           PointerType::getUnqual(IntegerType::Int8Ty), NULL));
 142
 143     //brainf.aberror:
 144     aberrorbb = new BasicBlock(label, brainf_func);
 145
 146     //call i32 @puts(i8 *getelementptr([%d x i8] *@aberrormsg, i32 0, i32 0))
 147     {
 148       Constant *zero_32 = Constant::getNullValue(IntegerType::Int32Ty);
 149
 150       Constant *gep_params[] = {
 151         zero_32,
 152         zero_32
 153       };
 154
 155       Constant *msgptr = ConstantExpr::
 156         getGetElementPtr(aberrormsg, gep_params,
 157                          array_lengthof(gep_params));
 158
 159       Value *puts_params[] = {
 160         msgptr
 161       };
 162
 163       CallInst *puts_call =
 164         new CallInst(puts_func,
 165                      puts_params, array_endof(puts_params),
 166                      "", aberrorbb);
 167       puts_call->setTailCall(false);
 168     }
 169
 170     //br label %brainf.end
 171     new BranchInst(endbb, aberrorbb);
 172   }
 173 }
 174
 175 void BrainF::readloop(PHINode *phi, BasicBlock *oldbb, BasicBlock *testbb) {
 176   Symbol cursym = SYM_NONE;
 177   int curvalue = 0;
 178   Symbol nextsym = SYM_NONE;
 179   int nextvalue = 0;
 180   char c;
 181   int loop;
 182   int direction;
 183
 184   while(cursym != SYM_EOF && cursym != SYM_ENDLOOP) {
 185     // Write out commands
 186     switch(cursym) {
 187       case SYM_NONE:
 188         // Do nothing
 189         break;
 190
 191       case SYM_READ:
 192         {
 193           //%tape.%d = call i32 @getchar()
 194           CallInst *getchar_call = builder->CreateCall(getchar_func, tapereg);
 195           getchar_call->setTailCall(false);
 196           Value *tape_0 = getchar_call;
 197
 198           //%tape.%d = trunc i32 %tape.%d to i8
 199           TruncInst *tape_1 = builder->
 200             CreateTrunc(tape_0, IntegerType::Int8Ty, tapereg);
 201
 202           //store i8 %tape.%d, i8 *%head.%d
 203           builder->CreateStore(tape_1, curhead);
 204         }
 205         break;
 206
 207       case SYM_WRITE:
 208         {
 209           //%tape.%d = load i8 *%head.%d
 210           LoadInst *tape_0 = builder->CreateLoad(curhead, tapereg);
 211
 212           //%tape.%d = sext i8 %tape.%d to i32
 213           SExtInst *tape_1 = builder->
 214             CreateSExt(tape_0, IntegerType::Int32Ty, tapereg);
 215
 216           //call i32 @putchar(i32 %tape.%d)
 217           Value *putchar_params[] = {
 218             tape_1
 219           };
 220           CallInst *putchar_call = builder->
 221             CreateCall(putchar_func,
 222                        putchar_params, array_endof(putchar_params));
 223           putchar_call->setTailCall(false);
 224         }
 225         break;
 226
 227       case SYM_MOVE:
 228         {
 229           //%head.%d = getelementptr i8 *%head.%d, i32 %d
 230           curhead = builder->
 231             CreateGEP(curhead, ConstantInt::get(APInt(32, curvalue)),
 232                       headreg);
 233
 234           //Error block for array out of bounds
 235           if (comflag & flag_arraybounds)
 236           {
 237             //%test.%d = icmp uge i8 *%head.%d, %arrmax
 238             ICmpInst *test_0 = builder->
 239               CreateICmpUGE(curhead, ptr_arrmax, testreg);
 240
 241             //%test.%d = icmp ult i8 *%head.%d, %arr
 242             ICmpInst *test_1 = builder->
 243               CreateICmpULT(curhead, ptr_arr, testreg);
 244
 245             //%test.%d = or i1 %test.%d, %test.%d
 246             BinaryOperator *test_2 = builder->
 247               CreateOr(test_0, test_1, testreg);
 248
 249             //br i1 %test.%d, label %main.%d, label %main.%d
 250             BasicBlock *nextbb = new BasicBlock(label, brainf_func);
 251             builder->CreateCondBr(test_2, aberrorbb, nextbb);
 252
 253             //main.%d:
 254             builder->SetInsertPoint(nextbb);
 255           }
 256         }
 257         break;
 258
 259       case SYM_CHANGE:
 260         {
 261           //%tape.%d = load i8 *%head.%d
 262           LoadInst *tape_0 = builder->CreateLoad(curhead, tapereg);
 263
 264           //%tape.%d = add i8 %tape.%d, %d
 265           BinaryOperator *tape_1 = builder->
 266             CreateAdd(tape_0, ConstantInt::get(APInt(8, curvalue)), tapereg);
 267
 268           //store i8 %tape.%d, i8 *%head.%d\n"
 269           builder->CreateStore(tape_1, curhead);
 270         }
 271         break;
 272
 273       case SYM_LOOP:
 274         {
 275           //br label %main.%d
 276           BasicBlock *testbb = new BasicBlock(label, brainf_func);
 277           builder->CreateBr(testbb);
 278
 279           //main.%d:
 280           BasicBlock *bb_0 = builder->GetInsertBlock();
 281           BasicBlock *bb_1 = new BasicBlock(label, brainf_func);
 282           builder->SetInsertPoint(bb_1);
 283
 284           //Make part of PHI instruction now, wait until end of loop to finish
 285           PHINode *phi_0 = new PHINode(PointerType::getUnqual(IntegerType::Int8Ty),
 286                                        headreg, testbb);
 287           phi_0->reserveOperandSpace(2);
 288           phi_0->addIncoming(curhead, bb_0);
 289           curhead = phi_0;
 290
 291           readloop(phi_0, bb_1, testbb);
 292         }
 293         break;
 294
 295       default:
 296         cerr<<"Error: Unknown symbol.\n";
 297         abort();
 298         break;
 299     }
 300
 301     cursym = nextsym;
 302     curvalue = nextvalue;
 303     nextsym = SYM_NONE;
 304
 305     // Reading stdin loop
 306     loop = (cursym == SYM_NONE)
 307         || (cursym == SYM_MOVE)
 308         || (cursym == SYM_CHANGE);
 309     while(loop) {
 310       *in>>c;
 311       if (in->eof()) {
 312         if (cursym == SYM_NONE) {
 313           cursym = SYM_EOF;
 314         } else {
 315           nextsym = SYM_EOF;
 316         }
 317         loop = 0;
 318       } else {
 319         direction = 1;
 320         switch(c) {
 321           case '-':
 322             direction = -1;
 323             // Fall through
 324
 325           case '+':
 326             if (cursym == SYM_CHANGE) {
 327               curvalue += direction;
 328               // loop = 1
 329             } else {
 330               if (cursym == SYM_NONE) {
 331                 cursym = SYM_CHANGE;
 332                 curvalue = direction;
 333                 // loop = 1
 334               } else {
 335                 nextsym = SYM_CHANGE;
 336                 nextvalue = direction;
 337                 loop = 0;
 338               }
 339             }
 340             break;
 341
 342           case '<':
 343             direction = -1;
 344             // Fall through
 345
 346           case '>':
 347             if (cursym == SYM_MOVE) {
 348               curvalue += direction;
 349               // loop = 1
 350             } else {
 351               if (cursym == SYM_NONE) {
 352                 cursym = SYM_MOVE;
 353                 curvalue = direction;
 354                 // loop = 1
 355               } else {
 356                 nextsym = SYM_MOVE;
 357                 nextvalue = direction;
 358                 loop = 0;
 359               }
 360             }
 361             break;
 362
 363           case ',':
 364             if (cursym == SYM_NONE) {
 365               cursym = SYM_READ;
 366             } else {
 367               nextsym = SYM_READ;
 368             }
 369             loop = 0;
 370             break;
 371
 372           case '.':
 373             if (cursym == SYM_NONE) {
 374               cursym = SYM_WRITE;
 375             } else {
 376               nextsym = SYM_WRITE;
 377             }
 378             loop = 0;
 379             break;
 380
 381           case '[':
 382             if (cursym == SYM_NONE) {
 383               cursym = SYM_LOOP;
 384             } else {
 385               nextsym = SYM_LOOP;
 386             }
 387             loop = 0;
 388             break;
 389
 390           case ']':
 391             if (cursym == SYM_NONE) {
 392               cursym = SYM_ENDLOOP;
 393             } else {
 394               nextsym = SYM_ENDLOOP;
 395             }
 396             loop = 0;
 397             break;
 398
 399           // Ignore other characters
 400           default:
 401             break;
 402         }
 403       }
 404     }
 405   }
 406
 407   if (cursym == SYM_ENDLOOP) {
 408     if (!phi) {
 409       cerr<<"Error: Extra ']'\n";
 410       abort();
 411     }
 412
 413     // Write loop test
 414     {
 415       //br label %main.%d
 416       builder->CreateBr(testbb);
 417
 418       //main.%d:
 419
 420       //%head.%d = phi i8 *[%head.%d, %main.%d], [%head.%d, %main.%d]
 421       //Finish phi made at beginning of loop
 422       phi->addIncoming(curhead, builder->GetInsertBlock());
 423       Value *head_0 = phi;
 424
 425       //%tape.%d = load i8 *%head.%d
 426       LoadInst *tape_0 = new LoadInst(head_0, tapereg, testbb);
 427
 428       //%test.%d = icmp eq i8 %tape.%d, 0
 429       ICmpInst *test_0 = new ICmpInst(ICmpInst::ICMP_EQ, tape_0,
 430                                       ConstantInt::get(APInt(8, 0)), testreg,
 431                                       testbb);
 432
 433       //br i1 %test.%d, label %main.%d, label %main.%d
 434       BasicBlock *bb_0 = new BasicBlock(label, brainf_func);
 435       new BranchInst(bb_0, oldbb, test_0, testbb);
 436
 437       //main.%d:
 438       builder->SetInsertPoint(bb_0);
 439
 440       //%head.%d = phi i8 *[%head.%d, %main.%d]
 441       PHINode *phi_1 = builder->
 442         CreatePHI(PointerType::getUnqual(IntegerType::Int8Ty), headreg);
 443       phi_1->reserveOperandSpace(1);
 444       phi_1->addIncoming(head_0, testbb);
 445       curhead = phi_1;
 446     }
 447
 448     return;
 449   }
 450
 451   //End of the program, so go to return block
 452   builder->CreateBr(endbb);
 453
 454   if (phi) {
 455     cerr<<"Error: Missing ']'\n";
 456     abort();
 457   }
 458 }