1 //===- PHITransAddr.cpp - PHI Translation for Addresses -------------------===// 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 PHITransAddr class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Analysis/PHITransAddr.h" 15 #include "llvm/Constants.h" 16 #include "llvm/Instructions.h" 17 #include "llvm/Analysis/Dominators.h" 18 #include "llvm/Analysis/InstructionSimplify.h" 19 #include "llvm/Support/Debug.h" 20 #include "llvm/Support/ErrorHandling.h" 21 #include "llvm/Support/raw_ostream.h" 22 using namespace llvm; 23 24 static bool CanPHITrans(Instruction *Inst) { 25 if (isa<PHINode>(Inst) || 26 isa<GetElementPtrInst>(Inst)) 27 return true; 28 29 if (isa<CastInst>(Inst) && 30 Inst->isSafeToSpeculativelyExecute()) 31 return true; 32 33 if (Inst->getOpcode() == Instruction::Add && 34 isa<ConstantInt>(Inst->getOperand(1))) 35 return true; 36 37 // cerr << "MEMDEP: Could not PHI translate: " << *Pointer; 38 // if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst)) 39 // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0); 40 return false; 41 } 42 43 void PHITransAddr::dump() const { 44 if (Addr == 0) { 45 dbgs() << "PHITransAddr: null\n"; 46 return; 47 } 48 dbgs() << "PHITransAddr: " << *Addr << "\n"; 49 for (unsigned i = 0, e = InstInputs.size(); i != e; ++i) 50 dbgs() << " Input #" << i << " is " << *InstInputs[i] << "\n"; 51 } 52 53 54 static bool VerifySubExpr(Value *Expr, 55 SmallVectorImpl<Instruction*> &InstInputs) { 56 // If this is a non-instruction value, there is nothing to do. 57 Instruction *I = dyn_cast<Instruction>(Expr); 58 if (I == 0) return true; 59 60 // If it's an instruction, it is either in Tmp or its operands recursively 61 // are. 62 SmallVectorImpl<Instruction*>::iterator Entry = 63 std::find(InstInputs.begin(), InstInputs.end(), I); 64 if (Entry != InstInputs.end()) { 65 InstInputs.erase(Entry); 66 return true; 67 } 68 69 // If it isn't in the InstInputs list it is a subexpr incorporated into the 70 // address. Sanity check that it is phi translatable. 71 if (!CanPHITrans(I)) { 72 errs() << "Non phi translatable instruction found in PHITransAddr:\n"; 73 errs() << *I << '\n'; 74 llvm_unreachable("Either something is missing from InstInputs or " 75 "CanPHITrans is wrong."); 76 return false; 77 } 78 79 // Validate the operands of the instruction. 80 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) 81 if (!VerifySubExpr(I->getOperand(i), InstInputs)) 82 return false; 83 84 return true; 85 } 86 87 /// Verify - Check internal consistency of this data structure. If the 88 /// structure is valid, it returns true. If invalid, it prints errors and 89 /// returns false. 90 bool PHITransAddr::Verify() const { 91 if (Addr == 0) return true; 92 93 SmallVector<Instruction*, 8> Tmp(InstInputs.begin(), InstInputs.end()); 94 95 if (!VerifySubExpr(Addr, Tmp)) 96 return false; 97 98 if (!Tmp.empty()) { 99 errs() << "PHITransAddr contains extra instructions:\n"; 100 for (unsigned i = 0, e = InstInputs.size(); i != e; ++i) 101 errs() << " InstInput #" << i << " is " << *InstInputs[i] << "\n"; 102 llvm_unreachable("This is unexpected."); 103 return false; 104 } 105 106 // a-ok. 107 return true; 108 } 109 110 111 /// IsPotentiallyPHITranslatable - If this needs PHI translation, return true 112 /// if we have some hope of doing it. This should be used as a filter to 113 /// avoid calling PHITranslateValue in hopeless situations. 114 bool PHITransAddr::IsPotentiallyPHITranslatable() const { 115 // If the input value is not an instruction, or if it is not defined in CurBB, 116 // then we don't need to phi translate it. 117 Instruction *Inst = dyn_cast<Instruction>(Addr); 118 return Inst == 0 || CanPHITrans(Inst); 119 } 120 121 122 static void RemoveInstInputs(Value *V, 123 SmallVectorImpl<Instruction*> &InstInputs) { 124 Instruction *I = dyn_cast<Instruction>(V); 125 if (I == 0) return; 126 127 // If the instruction is in the InstInputs list, remove it. 128 SmallVectorImpl<Instruction*>::iterator Entry = 129 std::find(InstInputs.begin(), InstInputs.end(), I); 130 if (Entry != InstInputs.end()) { 131 InstInputs.erase(Entry); 132 return; 133 } 134 135 assert(!isa<PHINode>(I) && "Error, removing something that isn't an input"); 136 137 // Otherwise, it must have instruction inputs itself. Zap them recursively. 138 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { 139 if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i))) 140 RemoveInstInputs(Op, InstInputs); 141 } 142 } 143 144 Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB, 145 BasicBlock *PredBB, 146 const DominatorTree *DT) { 147 // If this is a non-instruction value, it can't require PHI translation. 148 Instruction *Inst = dyn_cast<Instruction>(V); 149 if (Inst == 0) return V; 150 151 // Determine whether 'Inst' is an input to our PHI translatable expression. 152 bool isInput = std::count(InstInputs.begin(), InstInputs.end(), Inst); 153 154 // Handle inputs instructions if needed. 155 if (isInput) { 156 if (Inst->getParent() != CurBB) { 157 // If it is an input defined in a different block, then it remains an 158 // input. 159 return Inst; 160 } 161 162 // If 'Inst' is defined in this block and is an input that needs to be phi 163 // translated, we need to incorporate the value into the expression or fail. 164 165 // In either case, the instruction itself isn't an input any longer. 166 InstInputs.erase(std::find(InstInputs.begin(), InstInputs.end(), Inst)); 167 168 // If this is a PHI, go ahead and translate it. 169 if (PHINode *PN = dyn_cast<PHINode>(Inst)) 170 return AddAsInput(PN->getIncomingValueForBlock(PredBB)); 171 172 // If this is a non-phi value, and it is analyzable, we can incorporate it 173 // into the expression by making all instruction operands be inputs. 174 if (!CanPHITrans(Inst)) 175 return 0; 176 177 // All instruction operands are now inputs (and of course, they may also be 178 // defined in this block, so they may need to be phi translated themselves. 179 for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i) 180 if (Instruction *Op = dyn_cast<Instruction>(Inst->getOperand(i))) 181 InstInputs.push_back(Op); 182 } 183 184 // Ok, it must be an intermediate result (either because it started that way 185 // or because we just incorporated it into the expression). See if its 186 // operands need to be phi translated, and if so, reconstruct it. 187 188 if (CastInst *Cast = dyn_cast<CastInst>(Inst)) { 189 if (!Cast->isSafeToSpeculativelyExecute()) return 0; 190 Value *PHIIn = PHITranslateSubExpr(Cast->getOperand(0), CurBB, PredBB, DT); 191 if (PHIIn == 0) return 0; 192 if (PHIIn == Cast->getOperand(0)) 193 return Cast; 194 195 // Find an available version of this cast. 196 197 // Constants are trivial to find. 198 if (Constant *C = dyn_cast<Constant>(PHIIn)) 199 return AddAsInput(ConstantExpr::getCast(Cast->getOpcode(), 200 C, Cast->getType())); 201 202 // Otherwise we have to see if a casted version of the incoming pointer 203 // is available. If so, we can use it, otherwise we have to fail. 204 for (Value::use_iterator UI = PHIIn->use_begin(), E = PHIIn->use_end(); 205 UI != E; ++UI) { 206 if (CastInst *CastI = dyn_cast<CastInst>(*UI)) 207 if (CastI->getOpcode() == Cast->getOpcode() && 208 CastI->getType() == Cast->getType() && 209 (!DT || DT->dominates(CastI->getParent(), PredBB))) 210 return CastI; 211 } 212 return 0; 213 } 214 215 // Handle getelementptr with at least one PHI translatable operand. 216 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { 217 SmallVector<Value*, 8> GEPOps; 218 bool AnyChanged = false; 219 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) { 220 Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB, DT); 221 if (GEPOp == 0) return 0; 222 223 AnyChanged |= GEPOp != GEP->getOperand(i); 224 GEPOps.push_back(GEPOp); 225 } 226 227 if (!AnyChanged) 228 return GEP; 229 230 // Simplify the GEP to handle 'gep x, 0' -> x etc. 231 if (Value *V = SimplifyGEPInst(GEPOps, TD, DT)) { 232 for (unsigned i = 0, e = GEPOps.size(); i != e; ++i) 233 RemoveInstInputs(GEPOps[i], InstInputs); 234 235 return AddAsInput(V); 236 } 237 238 // Scan to see if we have this GEP available. 239 Value *APHIOp = GEPOps[0]; 240 for (Value::use_iterator UI = APHIOp->use_begin(), E = APHIOp->use_end(); 241 UI != E; ++UI) { 242 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) 243 if (GEPI->getType() == GEP->getType() && 244 GEPI->getNumOperands() == GEPOps.size() && 245 GEPI->getParent()->getParent() == CurBB->getParent() && 246 (!DT || DT->dominates(GEPI->getParent(), PredBB))) { 247 bool Mismatch = false; 248 for (unsigned i = 0, e = GEPOps.size(); i != e; ++i) 249 if (GEPI->getOperand(i) != GEPOps[i]) { 250 Mismatch = true; 251 break; 252 } 253 if (!Mismatch) 254 return GEPI; 255 } 256 } 257 return 0; 258 } 259 260 // Handle add with a constant RHS. 261 if (Inst->getOpcode() == Instruction::Add && 262 isa<ConstantInt>(Inst->getOperand(1))) { 263 // PHI translate the LHS. 264 Constant *RHS = cast<ConstantInt>(Inst->getOperand(1)); 265 bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap(); 266 bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap(); 267 268 Value *LHS = PHITranslateSubExpr(Inst->getOperand(0), CurBB, PredBB, DT); 269 if (LHS == 0) return 0; 270 271 // If the PHI translated LHS is an add of a constant, fold the immediates. 272 if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS)) 273 if (BOp->getOpcode() == Instruction::Add) 274 if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) { 275 LHS = BOp->getOperand(0); 276 RHS = ConstantExpr::getAdd(RHS, CI); 277 isNSW = isNUW = false; 278 279 // If the old 'LHS' was an input, add the new 'LHS' as an input. 280 if (std::count(InstInputs.begin(), InstInputs.end(), BOp)) { 281 RemoveInstInputs(BOp, InstInputs); 282 AddAsInput(LHS); 283 } 284 } 285 286 // See if the add simplifies away. 287 if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, TD, DT)) { 288 // If we simplified the operands, the LHS is no longer an input, but Res 289 // is. 290 RemoveInstInputs(LHS, InstInputs); 291 return AddAsInput(Res); 292 } 293 294 // If we didn't modify the add, just return it. 295 if (LHS == Inst->getOperand(0) && RHS == Inst->getOperand(1)) 296 return Inst; 297 298 // Otherwise, see if we have this add available somewhere. 299 for (Value::use_iterator UI = LHS->use_begin(), E = LHS->use_end(); 300 UI != E; ++UI) { 301 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(*UI)) 302 if (BO->getOpcode() == Instruction::Add && 303 BO->getOperand(0) == LHS && BO->getOperand(1) == RHS && 304 BO->getParent()->getParent() == CurBB->getParent() && 305 (!DT || DT->dominates(BO->getParent(), PredBB))) 306 return BO; 307 } 308 309 return 0; 310 } 311 312 // Otherwise, we failed. 313 return 0; 314 } 315 316 317 /// PHITranslateValue - PHI translate the current address up the CFG from 318 /// CurBB to Pred, updating our state to reflect any needed changes. If the 319 /// dominator tree DT is non-null, the translated value must dominate 320 /// PredBB. This returns true on failure and sets Addr to null. 321 bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB, 322 const DominatorTree *DT) { 323 assert(Verify() && "Invalid PHITransAddr!"); 324 Addr = PHITranslateSubExpr(Addr, CurBB, PredBB, DT); 325 assert(Verify() && "Invalid PHITransAddr!"); 326 327 if (DT) { 328 // Make sure the value is live in the predecessor. 329 if (Instruction *Inst = dyn_cast_or_null<Instruction>(Addr)) 330 if (!DT->dominates(Inst->getParent(), PredBB)) 331 Addr = 0; 332 } 333 334 return Addr == 0; 335 } 336 337 /// PHITranslateWithInsertion - PHI translate this value into the specified 338 /// predecessor block, inserting a computation of the value if it is 339 /// unavailable. 340 /// 341 /// All newly created instructions are added to the NewInsts list. This 342 /// returns null on failure. 343 /// 344 Value *PHITransAddr:: 345 PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB, 346 const DominatorTree &DT, 347 SmallVectorImpl<Instruction*> &NewInsts) { 348 unsigned NISize = NewInsts.size(); 349 350 // Attempt to PHI translate with insertion. 351 Addr = InsertPHITranslatedSubExpr(Addr, CurBB, PredBB, DT, NewInsts); 352 353 // If successful, return the new value. 354 if (Addr) return Addr; 355 356 // If not, destroy any intermediate instructions inserted. 357 while (NewInsts.size() != NISize) 358 NewInsts.pop_back_val()->eraseFromParent(); 359 return 0; 360 } 361 362 363 /// InsertPHITranslatedPointer - Insert a computation of the PHI translated 364 /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB 365 /// block. All newly created instructions are added to the NewInsts list. 366 /// This returns null on failure. 367 /// 368 Value *PHITransAddr:: 369 InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB, 370 BasicBlock *PredBB, const DominatorTree &DT, 371 SmallVectorImpl<Instruction*> &NewInsts) { 372 // See if we have a version of this value already available and dominating 373 // PredBB. If so, there is no need to insert a new instance of it. 374 PHITransAddr Tmp(InVal, TD); 375 if (!Tmp.PHITranslateValue(CurBB, PredBB, &DT)) 376 return Tmp.getAddr(); 377 378 // If we don't have an available version of this value, it must be an 379 // instruction. 380 Instruction *Inst = cast<Instruction>(InVal); 381 382 // Handle cast of PHI translatable value. 383 if (CastInst *Cast = dyn_cast<CastInst>(Inst)) { 384 if (!Cast->isSafeToSpeculativelyExecute()) return 0; 385 Value *OpVal = InsertPHITranslatedSubExpr(Cast->getOperand(0), 386 CurBB, PredBB, DT, NewInsts); 387 if (OpVal == 0) return 0; 388 389 // Otherwise insert a cast at the end of PredBB. 390 CastInst *New = CastInst::Create(Cast->getOpcode(), 391 OpVal, InVal->getType(), 392 InVal->getName()+".phi.trans.insert", 393 PredBB->getTerminator()); 394 NewInsts.push_back(New); 395 return New; 396 } 397 398 // Handle getelementptr with at least one PHI operand. 399 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { 400 SmallVector<Value*, 8> GEPOps; 401 BasicBlock *CurBB = GEP->getParent(); 402 for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) { 403 Value *OpVal = InsertPHITranslatedSubExpr(GEP->getOperand(i), 404 CurBB, PredBB, DT, NewInsts); 405 if (OpVal == 0) return 0; 406 GEPOps.push_back(OpVal); 407 } 408 409 GetElementPtrInst *Result = 410 GetElementPtrInst::Create(GEPOps[0], makeArrayRef(GEPOps).slice(1), 411 InVal->getName()+".phi.trans.insert", 412 PredBB->getTerminator()); 413 Result->setIsInBounds(GEP->isInBounds()); 414 NewInsts.push_back(Result); 415 return Result; 416 } 417 418 #if 0 419 // FIXME: This code works, but it is unclear that we actually want to insert 420 // a big chain of computation in order to make a value available in a block. 421 // This needs to be evaluated carefully to consider its cost trade offs. 422 423 // Handle add with a constant RHS. 424 if (Inst->getOpcode() == Instruction::Add && 425 isa<ConstantInt>(Inst->getOperand(1))) { 426 // PHI translate the LHS. 427 Value *OpVal = InsertPHITranslatedSubExpr(Inst->getOperand(0), 428 CurBB, PredBB, DT, NewInsts); 429 if (OpVal == 0) return 0; 430 431 BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1), 432 InVal->getName()+".phi.trans.insert", 433 PredBB->getTerminator()); 434 Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap()); 435 Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap()); 436 NewInsts.push_back(Res); 437 return Res; 438 } 439 #endif 440 441 return 0; 442 } 443