//===- PHITransAddr.cpp - PHI Translation for Addresses -------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the PHITransAddr class. // //===----------------------------------------------------------------------===// #include "llvm/Analysis/PHITransAddr.h" #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/Analysis/ValueTracking.h" #include "llvm/IR/Constants.h" #include "llvm/IR/Dominators.h" #include "llvm/IR/Instructions.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" using namespace llvm; static bool CanPHITrans(Instruction *Inst) { if (isa<PHINode>(Inst) || isa<GetElementPtrInst>(Inst)) return true; if (isa<CastInst>(Inst) && isSafeToSpeculativelyExecute(Inst)) return true; if (Inst->getOpcode() == Instruction::Add && isa<ConstantInt>(Inst->getOperand(1))) return true; // cerr << "MEMDEP: Could not PHI translate: " << *Pointer; // if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst)) // cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0); return false; } #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) void PHITransAddr::dump() const { if (!Addr) { dbgs() << "PHITransAddr: null\n"; return; } dbgs() << "PHITransAddr: " << *Addr << "\n"; for (unsigned i = 0, e = InstInputs.size(); i != e; ++i) dbgs() << " Input #" << i << " is " << *InstInputs[i] << "\n"; } #endif static bool VerifySubExpr(Value *Expr, SmallVectorImpl<Instruction*> &InstInputs) { // If this is a non-instruction value, there is nothing to do. Instruction *I = dyn_cast<Instruction>(Expr); if (!I) return true; // If it's an instruction, it is either in Tmp or its operands recursively // are. SmallVectorImpl<Instruction*>::iterator Entry = std::find(InstInputs.begin(), InstInputs.end(), I); if (Entry != InstInputs.end()) { InstInputs.erase(Entry); return true; } // If it isn't in the InstInputs list it is a subexpr incorporated into the // address. Sanity check that it is phi translatable. if (!CanPHITrans(I)) { errs() << "Instruction in PHITransAddr is not phi-translatable:\n"; errs() << *I << '\n'; llvm_unreachable("Either something is missing from InstInputs or " "CanPHITrans is wrong."); } // Validate the operands of the instruction. for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) if (!VerifySubExpr(I->getOperand(i), InstInputs)) return false; return true; } /// Verify - Check internal consistency of this data structure. If the /// structure is valid, it returns true. If invalid, it prints errors and /// returns false. bool PHITransAddr::Verify() const { if (!Addr) return true; SmallVector<Instruction*, 8> Tmp(InstInputs.begin(), InstInputs.end()); if (!VerifySubExpr(Addr, Tmp)) return false; if (!Tmp.empty()) { errs() << "PHITransAddr contains extra instructions:\n"; for (unsigned i = 0, e = InstInputs.size(); i != e; ++i) errs() << " InstInput #" << i << " is " << *InstInputs[i] << "\n"; llvm_unreachable("This is unexpected."); } // a-ok. return true; } /// IsPotentiallyPHITranslatable - If this needs PHI translation, return true /// if we have some hope of doing it. This should be used as a filter to /// avoid calling PHITranslateValue in hopeless situations. bool PHITransAddr::IsPotentiallyPHITranslatable() const { // If the input value is not an instruction, or if it is not defined in CurBB, // then we don't need to phi translate it. Instruction *Inst = dyn_cast<Instruction>(Addr); return !Inst || CanPHITrans(Inst); } static void RemoveInstInputs(Value *V, SmallVectorImpl<Instruction*> &InstInputs) { Instruction *I = dyn_cast<Instruction>(V); if (!I) return; // If the instruction is in the InstInputs list, remove it. SmallVectorImpl<Instruction*>::iterator Entry = std::find(InstInputs.begin(), InstInputs.end(), I); if (Entry != InstInputs.end()) { InstInputs.erase(Entry); return; } assert(!isa<PHINode>(I) && "Error, removing something that isn't an input"); // Otherwise, it must have instruction inputs itself. Zap them recursively. for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) { if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i))) RemoveInstInputs(Op, InstInputs); } } Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB, BasicBlock *PredBB, const DominatorTree *DT) { // If this is a non-instruction value, it can't require PHI translation. Instruction *Inst = dyn_cast<Instruction>(V); if (!Inst) return V; // Determine whether 'Inst' is an input to our PHI translatable expression. bool isInput = std::count(InstInputs.begin(), InstInputs.end(), Inst); // Handle inputs instructions if needed. if (isInput) { if (Inst->getParent() != CurBB) { // If it is an input defined in a different block, then it remains an // input. return Inst; } // If 'Inst' is defined in this block and is an input that needs to be phi // translated, we need to incorporate the value into the expression or fail. // In either case, the instruction itself isn't an input any longer. InstInputs.erase(std::find(InstInputs.begin(), InstInputs.end(), Inst)); // If this is a PHI, go ahead and translate it. if (PHINode *PN = dyn_cast<PHINode>(Inst)) return AddAsInput(PN->getIncomingValueForBlock(PredBB)); // If this is a non-phi value, and it is analyzable, we can incorporate it // into the expression by making all instruction operands be inputs. if (!CanPHITrans(Inst)) return nullptr; // All instruction operands are now inputs (and of course, they may also be // defined in this block, so they may need to be phi translated themselves. for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i) if (Instruction *Op = dyn_cast<Instruction>(Inst->getOperand(i))) InstInputs.push_back(Op); } // Ok, it must be an intermediate result (either because it started that way // or because we just incorporated it into the expression). See if its // operands need to be phi translated, and if so, reconstruct it. if (CastInst *Cast = dyn_cast<CastInst>(Inst)) { if (!isSafeToSpeculativelyExecute(Cast)) return nullptr; Value *PHIIn = PHITranslateSubExpr(Cast->getOperand(0), CurBB, PredBB, DT); if (!PHIIn) return nullptr; if (PHIIn == Cast->getOperand(0)) return Cast; // Find an available version of this cast. // Constants are trivial to find. if (Constant *C = dyn_cast<Constant>(PHIIn)) return AddAsInput(ConstantExpr::getCast(Cast->getOpcode(), C, Cast->getType())); // Otherwise we have to see if a casted version of the incoming pointer // is available. If so, we can use it, otherwise we have to fail. for (User *U : PHIIn->users()) { if (CastInst *CastI = dyn_cast<CastInst>(U)) if (CastI->getOpcode() == Cast->getOpcode() && CastI->getType() == Cast->getType() && (!DT || DT->dominates(CastI->getParent(), PredBB))) return CastI; } return nullptr; } // Handle getelementptr with at least one PHI translatable operand. if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { SmallVector<Value*, 8> GEPOps; bool AnyChanged = false; for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) { Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB, DT); if (!GEPOp) return nullptr; AnyChanged |= GEPOp != GEP->getOperand(i); GEPOps.push_back(GEPOp); } if (!AnyChanged) return GEP; // Simplify the GEP to handle 'gep x, 0' -> x etc. if (Value *V = SimplifyGEPInst(GEPOps, DL, TLI, DT, AC)) { for (unsigned i = 0, e = GEPOps.size(); i != e; ++i) RemoveInstInputs(GEPOps[i], InstInputs); return AddAsInput(V); } // Scan to see if we have this GEP available. Value *APHIOp = GEPOps[0]; for (User *U : APHIOp->users()) { if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) if (GEPI->getType() == GEP->getType() && GEPI->getNumOperands() == GEPOps.size() && GEPI->getParent()->getParent() == CurBB->getParent() && (!DT || DT->dominates(GEPI->getParent(), PredBB))) { bool Mismatch = false; for (unsigned i = 0, e = GEPOps.size(); i != e; ++i) if (GEPI->getOperand(i) != GEPOps[i]) { Mismatch = true; break; } if (!Mismatch) return GEPI; } } return nullptr; } // Handle add with a constant RHS. if (Inst->getOpcode() == Instruction::Add && isa<ConstantInt>(Inst->getOperand(1))) { // PHI translate the LHS. Constant *RHS = cast<ConstantInt>(Inst->getOperand(1)); bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap(); bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap(); Value *LHS = PHITranslateSubExpr(Inst->getOperand(0), CurBB, PredBB, DT); if (!LHS) return nullptr; // If the PHI translated LHS is an add of a constant, fold the immediates. if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS)) if (BOp->getOpcode() == Instruction::Add) if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) { LHS = BOp->getOperand(0); RHS = ConstantExpr::getAdd(RHS, CI); isNSW = isNUW = false; // If the old 'LHS' was an input, add the new 'LHS' as an input. if (std::count(InstInputs.begin(), InstInputs.end(), BOp)) { RemoveInstInputs(BOp, InstInputs); AddAsInput(LHS); } } // See if the add simplifies away. if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, DL, TLI, DT, AC)) { // If we simplified the operands, the LHS is no longer an input, but Res // is. RemoveInstInputs(LHS, InstInputs); return AddAsInput(Res); } // If we didn't modify the add, just return it. if (LHS == Inst->getOperand(0) && RHS == Inst->getOperand(1)) return Inst; // Otherwise, see if we have this add available somewhere. for (User *U : LHS->users()) { if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U)) if (BO->getOpcode() == Instruction::Add && BO->getOperand(0) == LHS && BO->getOperand(1) == RHS && BO->getParent()->getParent() == CurBB->getParent() && (!DT || DT->dominates(BO->getParent(), PredBB))) return BO; } return nullptr; } // Otherwise, we failed. return nullptr; } /// PHITranslateValue - PHI translate the current address up the CFG from /// CurBB to Pred, updating our state to reflect any needed changes. If the /// dominator tree DT is non-null, the translated value must dominate /// PredBB. This returns true on failure and sets Addr to null. bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB, const DominatorTree *DT) { assert(Verify() && "Invalid PHITransAddr!"); Addr = PHITranslateSubExpr(Addr, CurBB, PredBB, DT); assert(Verify() && "Invalid PHITransAddr!"); if (DT) { // Make sure the value is live in the predecessor. if (Instruction *Inst = dyn_cast_or_null<Instruction>(Addr)) if (!DT->dominates(Inst->getParent(), PredBB)) Addr = nullptr; } return Addr == nullptr; } /// PHITranslateWithInsertion - PHI translate this value into the specified /// predecessor block, inserting a computation of the value if it is /// unavailable. /// /// All newly created instructions are added to the NewInsts list. This /// returns null on failure. /// Value *PHITransAddr:: PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB, const DominatorTree &DT, SmallVectorImpl<Instruction*> &NewInsts) { unsigned NISize = NewInsts.size(); // Attempt to PHI translate with insertion. Addr = InsertPHITranslatedSubExpr(Addr, CurBB, PredBB, DT, NewInsts); // If successful, return the new value. if (Addr) return Addr; // If not, destroy any intermediate instructions inserted. while (NewInsts.size() != NISize) NewInsts.pop_back_val()->eraseFromParent(); return nullptr; } /// InsertPHITranslatedPointer - Insert a computation of the PHI translated /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB /// block. All newly created instructions are added to the NewInsts list. /// This returns null on failure. /// Value *PHITransAddr:: InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB, BasicBlock *PredBB, const DominatorTree &DT, SmallVectorImpl<Instruction*> &NewInsts) { // See if we have a version of this value already available and dominating // PredBB. If so, there is no need to insert a new instance of it. PHITransAddr Tmp(InVal, DL, AC); if (!Tmp.PHITranslateValue(CurBB, PredBB, &DT)) return Tmp.getAddr(); // If we don't have an available version of this value, it must be an // instruction. Instruction *Inst = cast<Instruction>(InVal); // Handle cast of PHI translatable value. if (CastInst *Cast = dyn_cast<CastInst>(Inst)) { if (!isSafeToSpeculativelyExecute(Cast)) return nullptr; Value *OpVal = InsertPHITranslatedSubExpr(Cast->getOperand(0), CurBB, PredBB, DT, NewInsts); if (!OpVal) return nullptr; // Otherwise insert a cast at the end of PredBB. CastInst *New = CastInst::Create(Cast->getOpcode(), OpVal, InVal->getType(), InVal->getName()+".phi.trans.insert", PredBB->getTerminator()); NewInsts.push_back(New); return New; } // Handle getelementptr with at least one PHI operand. if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { SmallVector<Value*, 8> GEPOps; BasicBlock *CurBB = GEP->getParent(); for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) { Value *OpVal = InsertPHITranslatedSubExpr(GEP->getOperand(i), CurBB, PredBB, DT, NewInsts); if (!OpVal) return nullptr; GEPOps.push_back(OpVal); } GetElementPtrInst *Result = GetElementPtrInst::Create( GEP->getSourceElementType(), GEPOps[0], makeArrayRef(GEPOps).slice(1), InVal->getName() + ".phi.trans.insert", PredBB->getTerminator()); Result->setIsInBounds(GEP->isInBounds()); NewInsts.push_back(Result); return Result; } #if 0 // FIXME: This code works, but it is unclear that we actually want to insert // a big chain of computation in order to make a value available in a block. // This needs to be evaluated carefully to consider its cost trade offs. // Handle add with a constant RHS. if (Inst->getOpcode() == Instruction::Add && isa<ConstantInt>(Inst->getOperand(1))) { // PHI translate the LHS. Value *OpVal = InsertPHITranslatedSubExpr(Inst->getOperand(0), CurBB, PredBB, DT, NewInsts); if (OpVal == 0) return 0; BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1), InVal->getName()+".phi.trans.insert", PredBB->getTerminator()); Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap()); Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap()); NewInsts.push_back(Res); return Res; } #endif return nullptr; }