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Diffstat (limited to 'contrib/llvm/lib/Analysis/PHITransAddr.cpp')
| -rw-r--r-- | contrib/llvm/lib/Analysis/PHITransAddr.cpp | 440 |
1 files changed, 440 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Analysis/PHITransAddr.cpp b/contrib/llvm/lib/Analysis/PHITransAddr.cpp new file mode 100644 index 000000000000..858f08f6537a --- /dev/null +++ b/contrib/llvm/lib/Analysis/PHITransAddr.cpp @@ -0,0 +1,440 @@ +//===- 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; +} |