| //===- 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/Config/llvm-config.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) |
| LLVM_DUMP_METHOD 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 = find(InstInputs, 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 = find(InstInputs, 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 = is_contained(InstInputs, 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(find(InstInputs, 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(GEP->getSourceElementType(), |
| 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))) { |
| if (std::equal(GEPOps.begin(), GEPOps.end(), GEPI->op_begin())) |
| 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 (is_contained(InstInputs, 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 |
| /// 'MustDominate' is true, 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, |
| bool MustDominate) { |
| assert(DT || !MustDominate); |
| assert(Verify() && "Invalid PHITransAddr!"); |
| if (DT && DT->isReachableFromEntry(PredBB)) |
| Addr = |
| PHITranslateSubExpr(Addr, CurBB, PredBB, MustDominate ? DT : nullptr); |
| else |
| Addr = nullptr; |
| assert(Verify() && "Invalid PHITransAddr!"); |
| |
| if (MustDominate) |
| // 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, /*MustDominate=*/true)) |
| return Tmp.getAddr(); |
| |
| // We don't need to PHI translate values which aren't instructions. |
| auto *Inst = dyn_cast<Instruction>(InVal); |
| if (!Inst) |
| return nullptr; |
| |
| // 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()); |
| New->setDebugLoc(Inst->getDebugLoc()); |
| 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->setDebugLoc(Inst->getDebugLoc()); |
| 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; |
| } |
