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   return isIdenticalToWhenDefined(I) &&
 172          SubclassOptionalData == I->SubclassOptionalData;
 173 }
 174
 175 /// isIdenticalToWhenDefined - This is like isIdenticalTo, except that it
 176 /// ignores the SubclassOptionalData flags, which specify conditions
 177 /// under which the instruction's result is undefined.
 178 bool Instruction::isIdenticalToWhenDefined(const Instruction *I) const {
 179   if (getOpcode() != I->getOpcode() ||
 180       getNumOperands() != I->getNumOperands() ||
 181       getType() != I->getType())
 182     return false;
 183
 184   // We have two instructions of identical opcode and #operands.  Check to see
 185   // if all operands are the same.
 186   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
 187     if (getOperand(i) != I->getOperand(i))
 188       return false;
 189
 190   // Check special state that is a part of some instructions.
 191   if (const LoadInst *LI = dyn_cast<LoadInst>(this))
 192     return LI->isVolatile() == cast<LoadInst>(I)->isVolatile() &&
 193            LI->getAlignment() == cast<LoadInst>(I)->getAlignment();
 194   if (const StoreInst *SI = dyn_cast<StoreInst>(this))
 195     return SI->isVolatile() == cast<StoreInst>(I)->isVolatile() &&
 196            SI->getAlignment() == cast<StoreInst>(I)->getAlignment();
 197   if (const CmpInst *CI = dyn_cast<CmpInst>(this))
 198     return CI->getPredicate() == cast<CmpInst>(I)->getPredicate();
 199   if (const CallInst *CI = dyn_cast<CallInst>(this))
 200     return CI->isTailCall() == cast<CallInst>(I)->isTailCall() &&
 201            CI->getCallingConv() == cast<CallInst>(I)->getCallingConv() &&
 202            CI->getAttributes().getRawPointer() ==
 203              cast<CallInst>(I)->getAttributes().getRawPointer();
 204   if (const InvokeInst *CI = dyn_cast<InvokeInst>(this))
 205     return CI->getCallingConv() == cast<InvokeInst>(I)->getCallingConv() &&
 206            CI->getAttributes().getRawPointer() ==
 207              cast<InvokeInst>(I)->getAttributes().getRawPointer();
 208   if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(this)) {
 209     if (IVI->getNumIndices() != cast<InsertValueInst>(I)->getNumIndices())
 210       return false;
 211     for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
 212       if (IVI->idx_begin()[i] != cast<InsertValueInst>(I)->idx_begin()[i])
 213         return false;
 214     return true;
 215   }
 216   if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(this)) {
 217     if (EVI->getNumIndices() != cast<ExtractValueInst>(I)->getNumIndices())
 218       return false;
 219     for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
 220       if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I)->idx_begin()[i])
 221         return false;
 222     return true;
 223   }
 224
 225   return true;
 226 }
 227
 228 // isSameOperationAs
 229 // This should be kept in sync with isEquivalentOperation in
 230 // lib/Transforms/IPO/MergeFunctions.cpp.
 231 bool Instruction::isSameOperationAs(const Instruction *I) const {
 232   if (getOpcode() != I->getOpcode() ||
 233       getNumOperands() != I->getNumOperands() ||
 234       getType() != I->getType())
 235     return false;
 236
 237   // We have two instructions of identical opcode and #operands.  Check to see
 238   // if all operands are the same type
 239   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
 240     if (getOperand(i)->getType() != I->getOperand(i)->getType())
 241       return false;
 242
 243   // Check special state that is a part of some instructions.
 244   if (const LoadInst *LI = dyn_cast<LoadInst>(this))
 245     return LI->isVolatile() == cast<LoadInst>(I)->isVolatile() &&
 246            LI->getAlignment() == cast<LoadInst>(I)->getAlignment();
 247   if (const StoreInst *SI = dyn_cast<StoreInst>(this))
 248     return SI->isVolatile() == cast<StoreInst>(I)->isVolatile() &&
 249            SI->getAlignment() == cast<StoreInst>(I)->getAlignment();
 250   if (const CmpInst *CI = dyn_cast<CmpInst>(this))
 251     return CI->getPredicate() == cast<CmpInst>(I)->getPredicate();
 252   if (const CallInst *CI = dyn_cast<CallInst>(this))
 253     return CI->isTailCall() == cast<CallInst>(I)->isTailCall() &&
 254            CI->getCallingConv() == cast<CallInst>(I)->getCallingConv() &&
 255            CI->getAttributes().getRawPointer() ==
 256              cast<CallInst>(I)->getAttributes().getRawPointer();
 257   if (const InvokeInst *CI = dyn_cast<InvokeInst>(this))
 258     return CI->getCallingConv() == cast<InvokeInst>(I)->getCallingConv() &&
 259            CI->getAttributes().getRawPointer() ==
 260              cast<InvokeInst>(I)->getAttributes().getRawPointer();
 261   if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(this)) {
 262     if (IVI->getNumIndices() != cast<InsertValueInst>(I)->getNumIndices())
 263       return false;
 264     for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
 265       if (IVI->idx_begin()[i] != cast<InsertValueInst>(I)->idx_begin()[i])
 266         return false;
 267     return true;
 268   }
 269   if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(this)) {
 270     if (EVI->getNumIndices() != cast<ExtractValueInst>(I)->getNumIndices())
 271       return false;
 272     for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
 273       if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I)->idx_begin()[i])
 274         return false;
 275     return true;
 276   }
 277
 278   return true;
 279 }
 280
 281 /// isUsedOutsideOfBlock - Return true if there are any uses of I outside of the
 282 /// specified block.  Note that PHI nodes are considered to evaluate their
 283 /// operands in the corresponding predecessor block.
 284 bool Instruction::isUsedOutsideOfBlock(const BasicBlock *BB) const {
 285   for (use_const_iterator UI = use_begin(), E = use_end(); UI != E; ++UI) {
 286     // PHI nodes uses values in the corresponding predecessor block.  For other
 287     // instructions, just check to see whether the parent of the use matches up.
 288     const PHINode *PN = dyn_cast<PHINode>(*UI);
 289     if (PN == 0) {
 290       if (cast<Instruction>(*UI)->getParent() != BB)
 291         return true;
 292       continue;
 293     }
 294
 295     if (PN->getIncomingBlock(UI) != BB)
 296       return true;
 297   }
 298   return false;
 299 }
 300
 301 /// mayReadFromMemory - Return true if this instruction may read memory.
 302 ///
 303 bool Instruction::mayReadFromMemory() const {
 304   switch (getOpcode()) {
 305   default: return false;
 306   case Instruction::Free:
 307   case Instruction::VAArg:
 308   case Instruction::Load:
 309     return true;
 310   case Instruction::Call:
 311     return !cast<CallInst>(this)->doesNotAccessMemory();
 312   case Instruction::Invoke:
 313     return !cast<InvokeInst>(this)->doesNotAccessMemory();
 314   case Instruction::Store:
 315     return cast<StoreInst>(this)->isVolatile();
 316   }
 317 }
 318
 319 /// mayWriteToMemory - Return true if this instruction may modify memory.
 320 ///
 321 bool Instruction::mayWriteToMemory() const {
 322   switch (getOpcode()) {
 323   default: return false;
 324   case Instruction::Free:
 325   case Instruction::Store:
 326   case Instruction::VAArg:
 327     return true;
 328   case Instruction::Call:
 329     return !cast<CallInst>(this)->onlyReadsMemory();
 330   case Instruction::Invoke:
 331     return !cast<InvokeInst>(this)->onlyReadsMemory();
 332   case Instruction::Load:
 333     return cast<LoadInst>(this)->isVolatile();
 334   }
 335 }
 336
 337 /// mayThrow - Return true if this instruction may throw an exception.
 338 ///
 339 bool Instruction::mayThrow() const {
 340   if (const CallInst *CI = dyn_cast<CallInst>(this))
 341     return !CI->doesNotThrow();
 342   return false;
 343 }
 344
 345 /// isAssociative - Return true if the instruction is associative:
 346 ///
 347 ///   Associative operators satisfy:  x op (y op z) === (x op y) op z
 348 ///
 349 /// In LLVM, the Add, Mul, And, Or, and Xor operators are associative.
 350 ///
 351 bool Instruction::isAssociative(unsigned Opcode, const Type *Ty) {
 352   return Opcode == And || Opcode == Or || Opcode == Xor ||
 353          Opcode == Add || Opcode == Mul;
 354 }
 355
 356 /// isCommutative - Return true if the instruction is commutative:
 357 ///
 358 ///   Commutative operators satisfy: (x op y) === (y op x)
 359 ///
 360 /// In LLVM, these are the associative operators, plus SetEQ and SetNE, when
 361 /// applied to any type.
 362 ///
 363 bool Instruction::isCommutative(unsigned op) {
 364   switch (op) {
 365   case Add:
 366   case FAdd:
 367   case Mul:
 368   case FMul:
 369   case And:
 370   case Or:
 371   case Xor:
 372     return true;
 373   default:
 374     return false;
 375   }
 376 }
 377
 378 bool Instruction::isSafeToSpeculativelyExecute() const {
 379   for (unsigned i = 0, e = getNumOperands(); i != e; ++i)
 380     if (Constant *C = dyn_cast<Constant>(getOperand(i)))
 381       if (C->canTrap())
 382         return false;
 383
 384   switch (getOpcode()) {
 385   default:
 386     return true;
 387   case UDiv:
 388   case URem: {
 389     // x / y is undefined if y == 0, but calcuations like x / 3 are safe.
 390     ConstantInt *Op = dyn_cast<ConstantInt>(getOperand(1));
 391     return Op && !Op->isNullValue();
 392   }
 393   case SDiv:
 394   case SRem: {
 395     // x / y is undefined if y == 0, and might be undefined if y == -1,
 396     // but calcuations like x / 3 are safe.
 397     ConstantInt *Op = dyn_cast<ConstantInt>(getOperand(1));
 398     return Op && !Op->isNullValue() && !Op->isAllOnesValue();
 399   }
 400   case Load: {
 401     if (cast<LoadInst>(this)->isVolatile())
 402       return false;
 403     if (isa<AllocationInst>(getOperand(0)))
 404       return true;
 405     if (GlobalVariable *GV = dyn_cast<GlobalVariable>(getOperand(0)))
 406       return !GV->hasExternalWeakLinkage();
 407     // FIXME: Handle cases involving GEPs.  We have to be careful because
 408     // a load of a out-of-bounds GEP has undefined behavior.
 409     return false;
 410   }
 411   case Call:
 412     return false; // The called function could have undefined behavior or
 413                   // side-effects.
 414                   // FIXME: We should special-case some intrinsics (bswap,
 415                   // overflow-checking arithmetic, etc.)
 416   case VAArg:
 417   case Alloca:
 418   case Malloc:
 419   case Invoke:
 420   case PHI:
 421   case Store:
 422   case Free:
 423   case Ret:
 424   case Br:
 425   case Switch:
 426   case Unwind:
 427   case Unreachable:
 428     return false; // Misc instructions which have effects
 429   }
 430 }