lib/VMCore/Instruction.cpp

   1 //===-- Instruction.cpp - Implement the Instruction class -----------------===//
   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 file implements the Instruction class for the VMCore library.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Type.h"
  15 #include "llvm/Instructions.h"
  16 #include "llvm/Function.h"
  17 #include "llvm/Constants.h"
  18 #include "llvm/GlobalVariable.h"
  19 #include "llvm/Support/CallSite.h"
  20 #include "llvm/Support/LeakDetector.h"
  21 using namespace llvm;
  22
  23 Instruction::Instruction(const Type *ty, unsigned it, Use *Ops, unsigned NumOps,
  24                          Instruction *InsertBefore)
  25   : User(ty, Value::InstructionVal + it, Ops, NumOps), Parent(0) {
  26   // Make sure that we get added to a basicblock
  27   LeakDetector::addGarbageObject(this);
  28
  29   // If requested, insert this instruction into a basic block...
  30   if (InsertBefore) {
  31     assert(InsertBefore->getParent() &&
  32            "Instruction to insert before is not in a basic block!");
  33     InsertBefore->getParent()->getInstList().insert(InsertBefore, this);
  34   }
  35 }
  36
  37 Instruction::Instruction(const Type *ty, unsigned it, Use *Ops, unsigned NumOps,
  38                          BasicBlock *InsertAtEnd)
  39   : User(ty, Value::InstructionVal + it, Ops, NumOps), Parent(0) {
  40   // Make sure that we get added to a basicblock
  41   LeakDetector::addGarbageObject(this);
  42
  43   // append this instruction into the basic block
  44   assert(InsertAtEnd && "Basic block to append to may not be NULL!");
  45   InsertAtEnd->getInstList().push_back(this);
  46 }
  47
  48
  49 // Out of line virtual method, so the vtable, etc has a home.
  50 Instruction::~Instruction() {
  51   assert(Parent == 0 && "Instruction still linked in the program!");
  52 }
  53
  54
  55 void Instruction::setParent(BasicBlock *P) {
  56   if (getParent()) {
  57     if (!P) LeakDetector::addGarbageObject(this);
  58   } else {
  59     if (P) LeakDetector::removeGarbageObject(this);
  60   }
  61
  62   Parent = P;
  63 }
  64
  65 void Instruction::removeFromParent() {
  66   getParent()->getInstList().remove(this);
  67 }
  68
  69 void Instruction::eraseFromParent() {
  70   getParent()->getInstList().erase(this);
  71 }
  72
  73 /// insertBefore - Insert an unlinked instructions into a basic block
  74 /// immediately before the specified instruction.
  75 void Instruction::insertBefore(Instruction *InsertPos) {
  76   InsertPos->getParent()->getInstList().insert(InsertPos, this);
  77 }
  78
  79 /// insertAfter - Insert an unlinked instructions into a basic block
  80 /// immediately after the specified instruction.
  81 void Instruction::insertAfter(Instruction *InsertPos) {
  82   InsertPos->getParent()->getInstList().insertAfter(InsertPos, this);
  83 }
  84
  85 /// moveBefore - Unlink this instruction from its current basic block and
  86 /// insert it into the basic block that MovePos lives in, right before
  87 /// MovePos.
  88 void Instruction::moveBefore(Instruction *MovePos) {
  89   MovePos->getParent()->getInstList().splice(MovePos,getParent()->getInstList(),
  90                                              this);
  91 }
  92
  93
  94 const char *Instruction::getOpcodeName(unsigned OpCode) {
  95   switch (OpCode) {
  96   // Terminators
  97   case Ret:    return "ret";
  98   case Br:     return "br";
  99   case Switch: return "switch";
 100   case Invoke: return "invoke";
 101   case Unwind: return "unwind";
 102   case Unreachable: return "unreachable";
 103
 104   // Standard binary operators...
 105   case Add: return "add";
 106   case FAdd: return "fadd";
 107   case Sub: return "sub";
 108   case FSub: return "fsub";
 109   case Mul: return "mul";
 110   case FMul: return "fmul";
 111   case UDiv: return "udiv";
 112   case SDiv: return "sdiv";
 113   case FDiv: return "fdiv";
 114   case URem: return "urem";
 115   case SRem: return "srem";
 116   case FRem: return "frem";
 117
 118   // Logical operators...
 119   case And: return "and";
 120   case Or : return "or";
 121   case Xor: return "xor";
 122
 123   // Memory instructions...
 124   case Malloc:        return "malloc";
 125   case Free:          return "free";
 126   case Alloca:        return "alloca";
 127   case Load:          return "load";
 128   case Store:         return "store";
 129   case GetElementPtr: return "getelementptr";
 130
 131   // Convert instructions...
 132   case Trunc:     return "trunc";
 133   case ZExt:      return "zext";
 134   case SExt:      return "sext";
 135   case FPTrunc:   return "fptrunc";
 136   case FPExt:     return "fpext";
 137   case FPToUI:    return "fptoui";
 138   case FPToSI:    return "fptosi";
 139   case UIToFP:    return "uitofp";
 140   case SIToFP:    return "sitofp";
 141   case IntToPtr:  return "inttoptr";
 142   case PtrToInt:  return "ptrtoint";
 143   case BitCast:   return "bitcast";
 144
 145   // Other instructions...
 146   case ICmp:           return "icmp";
 147   case FCmp:           return "fcmp";
 148   case PHI:            return "phi";
 149   case Select:         return "select";
 150   case Call:           return "call";
 151   case Shl:            return "shl";
 152   case LShr:           return "lshr";
 153   case AShr:           return "ashr";
 154   case VAArg:          return "va_arg";
 155   case ExtractElement: return "extractelement";
 156   case InsertElement:  return "insertelement";
 157   case ShuffleVector:  return "shufflevector";
 158   case ExtractValue:   return "extractvalue";
 159   case InsertValue:    return "insertvalue";
 160
 161   default: return "<Invalid operator> ";
 162   }
 163
 164   return 0;
 165 }
 166
 167 /// isIdenticalTo - Return true if the specified instruction is exactly
 168 /// identical to the current one.  This means that all operands match and any
 169 /// extra information (e.g. load is volatile) agree.
 170 bool Instruction::isIdenticalTo(const Instruction *I) const {
 171   if (getOpcode() != I->getOpcode() ||
 172       getNumOperands() != I->getNumOperands() ||
 173       getType() != I->getType())
 174     return false;
 175
 176   // We have two instructions of identical opcode and #operands.  Check to see
 177   // if all operands are the same.
 178   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
 179     if (getOperand(i) != I->getOperand(i))
 180       return false;
 181
 182   // Check special state that is a part of some instructions.
 183   if (const LoadInst *LI = dyn_cast<LoadInst>(this))
 184     return LI->isVolatile() == cast<LoadInst>(I)->isVolatile() &&
 185            LI->getAlignment() == cast<LoadInst>(I)->getAlignment();
 186   if (const StoreInst *SI = dyn_cast<StoreInst>(this))
 187     return SI->isVolatile() == cast<StoreInst>(I)->isVolatile() &&
 188            SI->getAlignment() == cast<StoreInst>(I)->getAlignment();
 189   if (const CmpInst *CI = dyn_cast<CmpInst>(this))
 190     return CI->getPredicate() == cast<CmpInst>(I)->getPredicate();
 191   if (const CallInst *CI = dyn_cast<CallInst>(this))
 192     return CI->isTailCall() == cast<CallInst>(I)->isTailCall() &&
 193            CI->getCallingConv() == cast<CallInst>(I)->getCallingConv() &&
 194            CI->getAttributes().getRawPointer() ==
 195              cast<CallInst>(I)->getAttributes().getRawPointer();
 196   if (const InvokeInst *CI = dyn_cast<InvokeInst>(this))
 197     return CI->getCallingConv() == cast<InvokeInst>(I)->getCallingConv() &&
 198            CI->getAttributes().getRawPointer() ==
 199              cast<InvokeInst>(I)->getAttributes().getRawPointer();
 200   if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(this)) {
 201     if (IVI->getNumIndices() != cast<InsertValueInst>(I)->getNumIndices())
 202       return false;
 203     for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
 204       if (IVI->idx_begin()[i] != cast<InsertValueInst>(I)->idx_begin()[i])
 205         return false;
 206     return true;
 207   }
 208   if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(this)) {
 209     if (EVI->getNumIndices() != cast<ExtractValueInst>(I)->getNumIndices())
 210       return false;
 211     for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
 212       if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I)->idx_begin()[i])
 213         return false;
 214     return true;
 215   }
 216
 217   return true;
 218 }
 219
 220 // isSameOperationAs
 221 // This should be kept in sync with isEquivalentOperation in
 222 // lib/Transforms/IPO/MergeFunctions.cpp.
 223 bool Instruction::isSameOperationAs(const Instruction *I) const {
 224   if (getOpcode() != I->getOpcode() ||
 225       getNumOperands() != I->getNumOperands() ||
 226       getType() != I->getType())
 227     return false;
 228
 229   // We have two instructions of identical opcode and #operands.  Check to see
 230   // if all operands are the same type
 231   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
 232     if (getOperand(i)->getType() != I->getOperand(i)->getType())
 233       return false;
 234
 235   // Check special state that is a part of some instructions.
 236   if (const LoadInst *LI = dyn_cast<LoadInst>(this))
 237     return LI->isVolatile() == cast<LoadInst>(I)->isVolatile() &&
 238            LI->getAlignment() == cast<LoadInst>(I)->getAlignment();
 239   if (const StoreInst *SI = dyn_cast<StoreInst>(this))
 240     return SI->isVolatile() == cast<StoreInst>(I)->isVolatile() &&
 241            SI->getAlignment() == cast<StoreInst>(I)->getAlignment();
 242   if (const CmpInst *CI = dyn_cast<CmpInst>(this))
 243     return CI->getPredicate() == cast<CmpInst>(I)->getPredicate();
 244   if (const CallInst *CI = dyn_cast<CallInst>(this))
 245     return CI->isTailCall() == cast<CallInst>(I)->isTailCall() &&
 246            CI->getCallingConv() == cast<CallInst>(I)->getCallingConv() &&
 247            CI->getAttributes().getRawPointer() ==
 248              cast<CallInst>(I)->getAttributes().getRawPointer();
 249   if (const InvokeInst *CI = dyn_cast<InvokeInst>(this))
 250     return CI->getCallingConv() == cast<InvokeInst>(I)->getCallingConv() &&
 251            CI->getAttributes().getRawPointer() ==
 252              cast<InvokeInst>(I)->getAttributes().getRawPointer();
 253   if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(this)) {
 254     if (IVI->getNumIndices() != cast<InsertValueInst>(I)->getNumIndices())
 255       return false;
 256     for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
 257       if (IVI->idx_begin()[i] != cast<InsertValueInst>(I)->idx_begin()[i])
 258         return false;
 259     return true;
 260   }
 261   if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(this)) {
 262     if (EVI->getNumIndices() != cast<ExtractValueInst>(I)->getNumIndices())
 263       return false;
 264     for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
 265       if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I)->idx_begin()[i])
 266         return false;
 267     return true;
 268   }
 269
 270   return true;
 271 }
 272
 273 /// isUsedOutsideOfBlock - Return true if there are any uses of I outside of the
 274 /// specified block.  Note that PHI nodes are considered to evaluate their
 275 /// operands in the corresponding predecessor block.
 276 bool Instruction::isUsedOutsideOfBlock(const BasicBlock *BB) const {
 277   for (use_const_iterator UI = use_begin(), E = use_end(); UI != E; ++UI) {
 278     // PHI nodes uses values in the corresponding predecessor block.  For other
 279     // instructions, just check to see whether the parent of the use matches up.
 280     const PHINode *PN = dyn_cast<PHINode>(*UI);
 281     if (PN == 0) {
 282       if (cast<Instruction>(*UI)->getParent() != BB)
 283         return true;
 284       continue;
 285     }
 286
 287     if (PN->getIncomingBlock(UI) != BB)
 288       return true;
 289   }
 290   return false;
 291 }
 292
 293 /// mayReadFromMemory - Return true if this instruction may read memory.
 294 ///
 295 bool Instruction::mayReadFromMemory() const {
 296   switch (getOpcode()) {
 297   default: return false;
 298   case Instruction::Free:
 299   case Instruction::VAArg:
 300   case Instruction::Load:
 301     return true;
 302   case Instruction::Call:
 303     return !cast<CallInst>(this)->doesNotAccessMemory();
 304   case Instruction::Invoke:
 305     return !cast<InvokeInst>(this)->doesNotAccessMemory();
 306   case Instruction::Store:
 307     return cast<StoreInst>(this)->isVolatile();
 308   }
 309 }
 310
 311 /// mayWriteToMemory - Return true if this instruction may modify memory.
 312 ///
 313 bool Instruction::mayWriteToMemory() const {
 314   switch (getOpcode()) {
 315   default: return false;
 316   case Instruction::Free:
 317   case Instruction::Store:
 318   case Instruction::VAArg:
 319     return true;
 320   case Instruction::Call:
 321     return !cast<CallInst>(this)->onlyReadsMemory();
 322   case Instruction::Invoke:
 323     return !cast<InvokeInst>(this)->onlyReadsMemory();
 324   case Instruction::Load:
 325     return cast<LoadInst>(this)->isVolatile();
 326   }
 327 }
 328
 329 /// mayThrow - Return true if this instruction may throw an exception.
 330 ///
 331 bool Instruction::mayThrow() const {
 332   if (const CallInst *CI = dyn_cast<CallInst>(this))
 333     return !CI->doesNotThrow();
 334   return false;
 335 }
 336
 337 /// isAssociative - Return true if the instruction is associative:
 338 ///
 339 ///   Associative operators satisfy:  x op (y op z) === (x op y) op z
 340 ///
 341 /// In LLVM, the Add, Mul, And, Or, and Xor operators are associative.
 342 ///
 343 bool Instruction::isAssociative(unsigned Opcode, const Type *Ty) {
 344   return Opcode == And || Opcode == Or || Opcode == Xor ||
 345          Opcode == Add || Opcode == Mul;
 346 }
 347
 348 /// isCommutative - Return true if the instruction is commutative:
 349 ///
 350 ///   Commutative operators satisfy: (x op y) === (y op x)
 351 ///
 352 /// In LLVM, these are the associative operators, plus SetEQ and SetNE, when
 353 /// applied to any type.
 354 ///
 355 bool Instruction::isCommutative(unsigned op) {
 356   switch (op) {
 357   case Add:
 358   case FAdd:
 359   case Mul:
 360   case FMul:
 361   case And:
 362   case Or:
 363   case Xor:
 364     return true;
 365   default:
 366     return false;
 367   }
 368 }
 369
 370 bool Instruction::isSafeToSpeculativelyExecute() const {
 371   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
 372     if (Constant *C = dyn_cast<Constant>(getOperand(i)))
 373       if (C->canTrap())
 374         return false;
 375
 376   switch (getOpcode()) {
 377   default:
 378     return true;
 379   case UDiv:
 380   case URem: {
 381     // x / y is undefined if y == 0, but calcuations like x / 3 are safe.
 382     ConstantInt *Op = dyn_cast<ConstantInt>(getOperand(1));
 383     return Op && !Op->isNullValue();
 384   }
 385   case SDiv:
 386   case SRem: {
 387     // x / y is undefined if y == 0, and might be undefined if y == -1,
 388     // but calcuations like x / 3 are safe.
 389     ConstantInt *Op = dyn_cast<ConstantInt>(getOperand(1));
 390     return Op && !Op->isNullValue() && !Op->isAllOnesValue();
 391   }
 392   case Load: {
 393     if (cast<LoadInst>(this)->isVolatile())
 394       return false;
 395     if (isa<AllocationInst>(getOperand(0)))
 396       return true;
 397     if (GlobalVariable *GV = dyn_cast<GlobalVariable>(getOperand(0)))
 398       return !GV->hasExternalWeakLinkage();
 399     // FIXME: Handle cases involving GEPs.  We have to be careful because
 400     // a load of a out-of-bounds GEP has undefined behavior.
 401     return false;
 402   }
 403   case Call:
 404     return false; // The called function could have undefined behavior or
 405                   // side-effects.
 406                   // FIXME: We should special-case some intrinsics (bswap,
 407                   // overflow-checking arithmetic, etc.)
 408   case VAArg:
 409   case Alloca:
 410   case Malloc:
 411   case Invoke:
 412   case PHI:
 413   case Store:
 414   case Free:
 415   case Ret:
 416   case Br:
 417   case Switch:
 418   case Unwind:
 419   case Unreachable:
 420     return false; // Misc instructions which have effects
 421   }
 422 }