LCOV - code coverage report
Current view: top level - lib/Analysis - PHITransAddr.cpp (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 113 139 81.3 %
Date: 2018-06-17 00:07:59 Functions: 7 9 77.8 %
Legend: Lines: hit not hit

          Line data    Source code
       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/Analysis/InstructionSimplify.h"
      16             : #include "llvm/Analysis/ValueTracking.h"
      17             : #include "llvm/Config/llvm-config.h"
      18             : #include "llvm/IR/Constants.h"
      19             : #include "llvm/IR/Dominators.h"
      20             : #include "llvm/IR/Instructions.h"
      21             : #include "llvm/Support/Debug.h"
      22             : #include "llvm/Support/ErrorHandling.h"
      23             : #include "llvm/Support/raw_ostream.h"
      24             : using namespace llvm;
      25             : 
      26      127316 : static bool CanPHITrans(Instruction *Inst) {
      27      127316 :   if (isa<PHINode>(Inst) ||
      28             :       isa<GetElementPtrInst>(Inst))
      29             :     return true;
      30             : 
      31       47410 :   if (isa<CastInst>(Inst) &&
      32        7438 :       isSafeToSpeculativelyExecute(Inst))
      33             :     return true;
      34             : 
      35       32950 :   if (Inst->getOpcode() == Instruction::Add &&
      36         416 :       isa<ConstantInt>(Inst->getOperand(1)))
      37             :     return true;
      38             : 
      39             :   //   cerr << "MEMDEP: Could not PHI translate: " << *Pointer;
      40             :   //   if (isa<BitCastInst>(PtrInst) || isa<GetElementPtrInst>(PtrInst))
      41             :   //     cerr << "OP:\t\t\t\t" << *PtrInst->getOperand(0);
      42             :   return false;
      43             : }
      44             : 
      45             : #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
      46             : LLVM_DUMP_METHOD void PHITransAddr::dump() const {
      47             :   if (!Addr) {
      48             :     dbgs() << "PHITransAddr: null\n";
      49             :     return;
      50             :   }
      51             :   dbgs() << "PHITransAddr: " << *Addr << "\n";
      52             :   for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
      53             :     dbgs() << "  Input #" << i << " is " << *InstInputs[i] << "\n";
      54             : }
      55             : #endif
      56             : 
      57             : 
      58           0 : static bool VerifySubExpr(Value *Expr,
      59             :                           SmallVectorImpl<Instruction*> &InstInputs) {
      60             :   // If this is a non-instruction value, there is nothing to do.
      61           0 :   Instruction *I = dyn_cast<Instruction>(Expr);
      62           0 :   if (!I) return true;
      63             : 
      64             :   // If it's an instruction, it is either in Tmp or its operands recursively
      65             :   // are.
      66             :   SmallVectorImpl<Instruction *>::iterator Entry = find(InstInputs, I);
      67           0 :   if (Entry != InstInputs.end()) {
      68           0 :     InstInputs.erase(Entry);
      69           0 :     return true;
      70             :   }
      71             : 
      72             :   // If it isn't in the InstInputs list it is a subexpr incorporated into the
      73             :   // address.  Sanity check that it is phi translatable.
      74           0 :   if (!CanPHITrans(I)) {
      75           0 :     errs() << "Instruction in PHITransAddr is not phi-translatable:\n";
      76           0 :     errs() << *I << '\n';
      77           0 :     llvm_unreachable("Either something is missing from InstInputs or "
      78             :                      "CanPHITrans is wrong.");
      79             :   }
      80             : 
      81             :   // Validate the operands of the instruction.
      82           0 :   for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
      83           0 :     if (!VerifySubExpr(I->getOperand(i), InstInputs))
      84             :       return false;
      85             : 
      86             :   return true;
      87             : }
      88             : 
      89             : /// Verify - Check internal consistency of this data structure.  If the
      90             : /// structure is valid, it returns true.  If invalid, it prints errors and
      91             : /// returns false.
      92           0 : bool PHITransAddr::Verify() const {
      93           0 :   if (!Addr) return true;
      94             : 
      95             :   SmallVector<Instruction*, 8> Tmp(InstInputs.begin(), InstInputs.end());
      96             : 
      97           0 :   if (!VerifySubExpr(Addr, Tmp))
      98             :     return false;
      99             : 
     100           0 :   if (!Tmp.empty()) {
     101           0 :     errs() << "PHITransAddr contains extra instructions:\n";
     102           0 :     for (unsigned i = 0, e = InstInputs.size(); i != e; ++i)
     103           0 :       errs() << "  InstInput #" << i << " is " << *InstInputs[i] << "\n";
     104           0 :     llvm_unreachable("This is unexpected.");
     105             :   }
     106             : 
     107             :   // a-ok.
     108             :   return true;
     109             : }
     110             : 
     111             : 
     112             : /// IsPotentiallyPHITranslatable - If this needs PHI translation, return true
     113             : /// if we have some hope of doing it.  This should be used as a filter to
     114             : /// avoid calling PHITranslateValue in hopeless situations.
     115       39364 : bool PHITransAddr::IsPotentiallyPHITranslatable() const {
     116             :   // If the input value is not an instruction, or if it is not defined in CurBB,
     117             :   // then we don't need to phi translate it.
     118       39364 :   Instruction *Inst = dyn_cast<Instruction>(Addr);
     119       39364 :   return !Inst || CanPHITrans(Inst);
     120             : }
     121             : 
     122             : 
     123        3082 : static void RemoveInstInputs(Value *V,
     124             :                              SmallVectorImpl<Instruction*> &InstInputs) {
     125        3082 :   Instruction *I = dyn_cast<Instruction>(V);
     126        6164 :   if (!I) return;
     127             : 
     128             :   // If the instruction is in the InstInputs list, remove it.
     129             :   SmallVectorImpl<Instruction *>::iterator Entry = find(InstInputs, I);
     130         188 :   if (Entry != InstInputs.end()) {
     131         188 :     InstInputs.erase(Entry);
     132         188 :     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           0 :   for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
     139           0 :     if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
     140           0 :       RemoveInstInputs(Op, InstInputs);
     141             :   }
     142             : }
     143             : 
     144      241751 : 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      241751 :   Instruction *Inst = dyn_cast<Instruction>(V);
     149      241751 :   if (!Inst) return V;
     150             : 
     151             :   // Determine whether 'Inst' is an input to our PHI translatable expression.
     152             :   bool isInput = is_contained(InstInputs, Inst);
     153             : 
     154             :   // Handle inputs instructions if needed.
     155      114799 :   if (isInput) {
     156      110704 :     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      194112 :     InstInputs.erase(find(InstInputs, Inst));
     167             : 
     168             :     // If this is a PHI, go ahead and translate it.
     169       97056 :     if (PHINode *PN = dyn_cast<PHINode>(Inst))
     170       18208 :       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       87952 :     if (!CanPHITrans(Inst))
     175             :       return nullptr;
     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      465360 :     for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
     180      353192 :       if (Instruction *Op = dyn_cast<Instruction>(Inst->getOperand(i)))
     181       52852 :         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       60179 :   if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
     189        5337 :     if (!isSafeToSpeculativelyExecute(Cast)) return nullptr;
     190        5337 :     Value *PHIIn = PHITranslateSubExpr(Cast->getOperand(0), CurBB, PredBB, DT);
     191        5337 :     if (!PHIIn) return nullptr;
     192        3711 :     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          24 :       return AddAsInput(ConstantExpr::getCast(Cast->getOpcode(),
     200          12 :                                               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        2531 :     for (User *U : PHIIn->users()) {
     205             :       if (CastInst *CastI = dyn_cast<CastInst>(U))
     206          73 :         if (CastI->getOpcode() == Cast->getOpcode() &&
     207         170 :             CastI->getType() == Cast->getType() &&
     208           0 :             (!DT || DT->dominates(CastI->getParent(), PredBB)))
     209             :           return CastI;
     210             :     }
     211             :     return nullptr;
     212             :   }
     213             : 
     214             :   // Handle getelementptr with at least one PHI translatable operand.
     215             :   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
     216             :     SmallVector<Value*, 8> GEPOps;
     217             :     bool AnyChanged = false;
     218      341014 :     for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
     219      175944 :       Value *GEPOp = PHITranslateSubExpr(GEP->getOperand(i), CurBB, PredBB, DT);
     220      175944 :       if (!GEPOp) return nullptr;
     221             : 
     222      143338 :       AnyChanged |= GEPOp != GEP->getOperand(i);
     223      143338 :       GEPOps.push_back(GEPOp);
     224             :     }
     225             : 
     226       21732 :     if (!AnyChanged)
     227             :       return GEP;
     228             : 
     229             :     // Simplify the GEP to handle 'gep x, 0' -> x etc.
     230       18054 :     if (Value *V = SimplifyGEPInst(GEP->getSourceElementType(),
     231        6018 :                                    GEPOps, {DL, TLI, DT, AC})) {
     232        3602 :       for (unsigned i = 0, e = GEPOps.size(); i != e; ++i)
     233        5572 :         RemoveInstInputs(GEPOps[i], InstInputs);
     234             : 
     235         816 :       return AddAsInput(V);
     236             :     }
     237             : 
     238             :     // Scan to see if we have this GEP available.
     239        5202 :     Value *APHIOp = GEPOps[0];
     240       42768 :     for (User *U : APHIOp->users()) {
     241             :       if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U))
     242       38888 :         if (GEPI->getType() == GEP->getType() &&
     243       24493 :             GEPI->getNumOperands() == GEPOps.size() &&
     244       43580 :             GEPI->getParent()->getParent() == CurBB->getParent() &&
     245         282 :             (!DT || DT->dominates(GEPI->getParent(), PredBB))) {
     246        5454 :           if (std::equal(GEPOps.begin(), GEPOps.end(), GEPI->op_begin()))
     247             :             return GEPI;
     248             :         }
     249             :     }
     250             :     return nullptr;
     251             :   }
     252             : 
     253             :   // Handle add with a constant RHS.
     254        1008 :   if (Inst->getOpcode() == Instruction::Add &&
     255         504 :       isa<ConstantInt>(Inst->getOperand(1))) {
     256             :     // PHI translate the LHS.
     257             :     Constant *RHS = cast<ConstantInt>(Inst->getOperand(1));
     258         504 :     bool isNSW = cast<BinaryOperator>(Inst)->hasNoSignedWrap();
     259         504 :     bool isNUW = cast<BinaryOperator>(Inst)->hasNoUnsignedWrap();
     260             : 
     261        1008 :     Value *LHS = PHITranslateSubExpr(Inst->getOperand(0), CurBB, PredBB, DT);
     262         504 :     if (!LHS) return nullptr;
     263             : 
     264             :     // If the PHI translated LHS is an add of a constant, fold the immediates.
     265         360 :     if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(LHS))
     266         134 :       if (BOp->getOpcode() == Instruction::Add)
     267             :         if (ConstantInt *CI = dyn_cast<ConstantInt>(BOp->getOperand(1))) {
     268             :           LHS = BOp->getOperand(0);
     269         132 :           RHS = ConstantExpr::getAdd(RHS, CI);
     270             :           isNSW = isNUW = false;
     271             : 
     272             :           // If the old 'LHS' was an input, add the new 'LHS' as an input.
     273         132 :           if (is_contained(InstInputs, BOp)) {
     274         132 :             RemoveInstInputs(BOp, InstInputs);
     275             :             AddAsInput(LHS);
     276             :           }
     277             :         }
     278             : 
     279             :     // See if the add simplifies away.
     280         720 :     if (Value *Res = SimplifyAddInst(LHS, RHS, isNSW, isNUW, {DL, TLI, DT, AC})) {
     281             :       // If we simplified the operands, the LHS is no longer an input, but Res
     282             :       // is.
     283         164 :       RemoveInstInputs(LHS, InstInputs);
     284         164 :       return AddAsInput(Res);
     285             :     }
     286             : 
     287             :     // If we didn't modify the add, just return it.
     288         581 :     if (LHS == Inst->getOperand(0) && RHS == Inst->getOperand(1))
     289             :       return Inst;
     290             : 
     291             :     // Otherwise, see if we have this add available somewhere.
     292         451 :     for (User *U : LHS->users()) {
     293             :       if (BinaryOperator *BO = dyn_cast<BinaryOperator>(U))
     294         203 :         if (BO->getOpcode() == Instruction::Add &&
     295         207 :             BO->getOperand(0) == LHS && BO->getOperand(1) == RHS &&
     296         211 :             BO->getParent()->getParent() == CurBB->getParent() &&
     297           0 :             (!DT || DT->dominates(BO->getParent(), PredBB)))
     298             :           return BO;
     299             :     }
     300             : 
     301             :     return nullptr;
     302             :   }
     303             : 
     304             :   // Otherwise, we failed.
     305             :   return nullptr;
     306             : }
     307             : 
     308             : 
     309             : /// PHITranslateValue - PHI translate the current address up the CFG from
     310             : /// CurBB to Pred, updating our state to reflect any needed changes.  If
     311             : /// 'MustDominate' is true, the translated value must dominate
     312             : /// PredBB.  This returns true on failure and sets Addr to null.
     313      307760 : bool PHITransAddr::PHITranslateValue(BasicBlock *CurBB, BasicBlock *PredBB,
     314             :                                      const DominatorTree *DT,
     315             :                                      bool MustDominate) {
     316             :   assert(DT || !MustDominate);
     317             :   assert(Verify() && "Invalid PHITransAddr!");
     318      307760 :   if (DT && DT->isReachableFromEntry(PredBB))
     319       59966 :     Addr =
     320      119932 :         PHITranslateSubExpr(Addr, CurBB, PredBB, MustDominate ? DT : nullptr);
     321             :   else
     322      247794 :     Addr = nullptr;
     323             :   assert(Verify() && "Invalid PHITransAddr!");
     324             : 
     325      307760 :   if (MustDominate)
     326             :     // Make sure the value is live in the predecessor.
     327        2935 :     if (Instruction *Inst = dyn_cast_or_null<Instruction>(Addr))
     328         767 :       if (!DT->dominates(Inst->getParent(), PredBB))
     329          92 :         Addr = nullptr;
     330             : 
     331      307760 :   return Addr == nullptr;
     332             : }
     333             : 
     334             : /// PHITranslateWithInsertion - PHI translate this value into the specified
     335             : /// predecessor block, inserting a computation of the value if it is
     336             : /// unavailable.
     337             : ///
     338             : /// All newly created instructions are added to the NewInsts list.  This
     339             : /// returns null on failure.
     340             : ///
     341        2423 : Value *PHITransAddr::
     342             : PHITranslateWithInsertion(BasicBlock *CurBB, BasicBlock *PredBB,
     343             :                           const DominatorTree &DT,
     344             :                           SmallVectorImpl<Instruction*> &NewInsts) {
     345             :   unsigned NISize = NewInsts.size();
     346             : 
     347             :   // Attempt to PHI translate with insertion.
     348        2423 :   Addr = InsertPHITranslatedSubExpr(Addr, CurBB, PredBB, DT, NewInsts);
     349             : 
     350             :   // If successful, return the new value.
     351        2423 :   if (Addr) return Addr;
     352             : 
     353             :   // If not, destroy any intermediate instructions inserted.
     354          29 :   while (NewInsts.size() != NISize)
     355           0 :     NewInsts.pop_back_val()->eraseFromParent();
     356             :   return nullptr;
     357             : }
     358             : 
     359             : 
     360             : /// InsertPHITranslatedPointer - Insert a computation of the PHI translated
     361             : /// version of 'V' for the edge PredBB->CurBB into the end of the PredBB
     362             : /// block.  All newly created instructions are added to the NewInsts list.
     363             : /// This returns null on failure.
     364             : ///
     365        2935 : Value *PHITransAddr::
     366             : InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
     367             :                            BasicBlock *PredBB, const DominatorTree &DT,
     368             :                            SmallVectorImpl<Instruction*> &NewInsts) {
     369             :   // See if we have a version of this value already available and dominating
     370             :   // PredBB.  If so, there is no need to insert a new instance of it.
     371        2935 :   PHITransAddr Tmp(InVal, DL, AC);
     372        2935 :   if (!Tmp.PHITranslateValue(CurBB, PredBB, &DT, /*MustDominate=*/true))
     373        2756 :     return Tmp.getAddr();
     374             : 
     375             :   // We don't need to PHI translate values which aren't instructions.
     376             :   auto *Inst = dyn_cast<Instruction>(InVal);
     377             :   if (!Inst)
     378             :     return nullptr;
     379             : 
     380             :   // Handle cast of PHI translatable value.
     381             :   if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
     382          15 :     if (!isSafeToSpeculativelyExecute(Cast)) return nullptr;
     383             :     Value *OpVal = InsertPHITranslatedSubExpr(Cast->getOperand(0),
     384          15 :                                               CurBB, PredBB, DT, NewInsts);
     385          15 :     if (!OpVal) return nullptr;
     386             : 
     387             :     // Otherwise insert a cast at the end of PredBB.
     388          14 :     CastInst *New = CastInst::Create(Cast->getOpcode(), OpVal, InVal->getType(),
     389          28 :                                      InVal->getName() + ".phi.trans.insert",
     390          14 :                                      PredBB->getTerminator());
     391          14 :     New->setDebugLoc(Inst->getDebugLoc());
     392          14 :     NewInsts.push_back(New);
     393          14 :     return New;
     394             :   }
     395             : 
     396             :   // Handle getelementptr with at least one PHI operand.
     397             :   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
     398             :     SmallVector<Value*, 8> GEPOps;
     399         135 :     BasicBlock *CurBB = GEP->getParent();
     400        1073 :     for (unsigned i = 0, e = GEP->getNumOperands(); i != e; ++i) {
     401         497 :       Value *OpVal = InsertPHITranslatedSubExpr(GEP->getOperand(i),
     402         497 :                                                 CurBB, PredBB, DT, NewInsts);
     403         497 :       if (!OpVal) return nullptr;
     404         469 :       GEPOps.push_back(OpVal);
     405             :     }
     406             : 
     407         107 :     GetElementPtrInst *Result = GetElementPtrInst::Create(
     408             :         GEP->getSourceElementType(), GEPOps[0], makeArrayRef(GEPOps).slice(1),
     409         214 :         InVal->getName() + ".phi.trans.insert", PredBB->getTerminator());
     410         107 :     Result->setDebugLoc(Inst->getDebugLoc());
     411         107 :     Result->setIsInBounds(GEP->isInBounds());
     412         107 :     NewInsts.push_back(Result);
     413         107 :     return Result;
     414             :   }
     415             : 
     416             : #if 0
     417             :   // FIXME: This code works, but it is unclear that we actually want to insert
     418             :   // a big chain of computation in order to make a value available in a block.
     419             :   // This needs to be evaluated carefully to consider its cost trade offs.
     420             : 
     421             :   // Handle add with a constant RHS.
     422             :   if (Inst->getOpcode() == Instruction::Add &&
     423             :       isa<ConstantInt>(Inst->getOperand(1))) {
     424             :     // PHI translate the LHS.
     425             :     Value *OpVal = InsertPHITranslatedSubExpr(Inst->getOperand(0),
     426             :                                               CurBB, PredBB, DT, NewInsts);
     427             :     if (OpVal == 0) return 0;
     428             : 
     429             :     BinaryOperator *Res = BinaryOperator::CreateAdd(OpVal, Inst->getOperand(1),
     430             :                                            InVal->getName()+".phi.trans.insert",
     431             :                                                     PredBB->getTerminator());
     432             :     Res->setHasNoSignedWrap(cast<BinaryOperator>(Inst)->hasNoSignedWrap());
     433             :     Res->setHasNoUnsignedWrap(cast<BinaryOperator>(Inst)->hasNoUnsignedWrap());
     434             :     NewInsts.push_back(Res);
     435             :     return Res;
     436             :   }
     437             : #endif
     438             : 
     439             :   return nullptr;
     440             : }

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