X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FTransforms%2FUtils%2FSimplifyCFG.cpp;h=0b9568b91dc965e6ab0fb29b000ad6b8ede26416;hp=318773d64c294144db8a49e91afa74b33f8e309f;hb=d5c2318adc7bde590d9f9369ef97fe7adde3f1a4;hpb=b3e705ed1daf9d63f9c099366e61b150c676b0f2 diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 318773d64c2..0b9568b91dc 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -73,6 +73,7 @@ STATISTIC(NumBitMaps, "Number of switch instructions turned into bitmaps"); STATISTIC(NumLinearMaps, "Number of switch instructions turned into linear mapping"); STATISTIC(NumLookupTables, "Number of switch instructions turned into lookup tables"); STATISTIC(NumLookupTablesHoles, "Number of switch instructions turned into lookup tables (holes checked)"); +STATISTIC(NumTableCmpReuses, "Number of reused switch table lookup compares"); STATISTIC(NumSinkCommons, "Number of common instructions sunk down to the end block"); STATISTIC(NumSpeculations, "Number of speculative executed instructions"); @@ -107,7 +108,7 @@ class SimplifyCFGOpt { const TargetTransformInfo &TTI; unsigned BonusInstThreshold; const DataLayout *const DL; - AssumptionTracker *AT; + AssumptionCache *AC; Value *isValueEqualityComparison(TerminatorInst *TI); BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI, std::vector &Cases); @@ -127,8 +128,8 @@ class SimplifyCFGOpt { public: SimplifyCFGOpt(const TargetTransformInfo &TTI, unsigned BonusInstThreshold, - const DataLayout *DL, AssumptionTracker *AT) - : TTI(TTI), BonusInstThreshold(BonusInstThreshold), DL(DL), AT(AT) {} + const DataLayout *DL, AssumptionCache *AC) + : TTI(TTI), BonusInstThreshold(BonusInstThreshold), DL(DL), AC(AC) {} bool run(BasicBlock *BB); }; } @@ -357,6 +358,8 @@ static ConstantInt *GetConstantInt(Value *V, const DataLayout *DL) { return nullptr; } +namespace { + /// Given a chain of or (||) or and (&&) comparison of a value against a /// constant, this will try to recover the information required for a switch /// structure. @@ -369,19 +372,22 @@ static ConstantInt *GetConstantInt(Value *V, const DataLayout *DL) { /// fail. struct ConstantComparesGatherer { - Value *CompValue = nullptr; /// Value found for the switch comparison - Value *Extra = nullptr; /// Extra clause to be checked before the switch - SmallVector Vals; /// Set of integers to match in switch - unsigned UsedICmps = 0; /// Number of comparisons matched in the and/or chain + Value *CompValue; /// Value found for the switch comparison + Value *Extra; /// Extra clause to be checked before the switch + SmallVector Vals; /// Set of integers to match in switch + unsigned UsedICmps; /// Number of comparisons matched in the and/or chain /// Construct and compute the result for the comparison instruction Cond - ConstantComparesGatherer(Instruction *Cond, const DataLayout *DL) { + ConstantComparesGatherer(Instruction *Cond, const DataLayout *DL) + : CompValue(nullptr), Extra(nullptr), UsedICmps(0) { gather(Cond, DL); } /// Prevent copy - ConstantComparesGatherer(const ConstantComparesGatherer&) = delete; - ConstantComparesGatherer &operator=(const ConstantComparesGatherer&) = delete; + ConstantComparesGatherer(const ConstantComparesGatherer &) + LLVM_DELETED_FUNCTION; + ConstantComparesGatherer & + operator=(const ConstantComparesGatherer &) LLVM_DELETED_FUNCTION; private: @@ -389,7 +395,8 @@ private: /// it wasn't set before or if the new value is the same as the old one bool setValueOnce(Value *NewVal) { if(CompValue && CompValue != NewVal) return false; - return CompValue = NewVal; + CompValue = NewVal; + return (CompValue != nullptr); } /// Try to match Instruction "I" as a comparison against a constant and @@ -522,6 +529,8 @@ private: } }; +} + static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) { Instruction *Cond = nullptr; if (SwitchInst *SI = dyn_cast(TI)) { @@ -704,8 +713,7 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, if (HasWeight) for (unsigned MD_i = 1, MD_e = MD->getNumOperands(); MD_i < MD_e; ++MD_i) { - ConstantInt* CI = dyn_cast(MD->getOperand(MD_i)); - assert(CI); + ConstantInt *CI = mdconst::extract(MD->getOperand(MD_i)); Weights.push_back(CI->getValue().getZExtValue()); } for (SwitchInst::CaseIt i = SI->case_end(), e = SI->case_begin(); i != e;) { @@ -810,7 +818,7 @@ static void GetBranchWeights(TerminatorInst *TI, MDNode *MD = TI->getMetadata(LLVMContext::MD_prof); assert(MD); for (unsigned i = 1, e = MD->getNumOperands(); i < e; ++i) { - ConstantInt *CI = cast(MD->getOperand(i)); + ConstantInt *CI = mdconst::extract(MD->getOperand(i)); Weights.push_back(CI->getValue().getZExtValue()); } @@ -1236,14 +1244,13 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { return false; // Gather the PHI nodes in BBEnd. - std::map > MapValueFromBB1ToBB2; + SmallDenseMap, PHINode *> JointValueMap; Instruction *FirstNonPhiInBBEnd = nullptr; - for (BasicBlock::iterator I = BBEnd->begin(), E = BBEnd->end(); - I != E; ++I) { + for (BasicBlock::iterator I = BBEnd->begin(), E = BBEnd->end(); I != E; ++I) { if (PHINode *PN = dyn_cast(I)) { Value *BB1V = PN->getIncomingValueForBlock(BB1); Value *BB2V = PN->getIncomingValueForBlock(BB2); - MapValueFromBB1ToBB2[BB1V] = std::make_pair(BB2V, PN); + JointValueMap[std::make_pair(BB1V, BB2V)] = PN; } else { FirstNonPhiInBBEnd = &*I; break; @@ -1252,13 +1259,13 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { if (!FirstNonPhiInBBEnd) return false; - // This does very trivial matching, with limited scanning, to find identical // instructions in the two blocks. We scan backward for obviously identical // instructions in an identical order. BasicBlock::InstListType::reverse_iterator RI1 = BB1->getInstList().rbegin(), - RE1 = BB1->getInstList().rend(), RI2 = BB2->getInstList().rbegin(), - RE2 = BB2->getInstList().rend(); + RE1 = BB1->getInstList().rend(), + RI2 = BB2->getInstList().rbegin(), + RE2 = BB2->getInstList().rend(); // Skip debug info. while (RI1 != RE1 && isa(&*RI1)) ++RI1; if (RI1 == RE1) @@ -1281,6 +1288,7 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { return Changed; Instruction *I1 = &*RI1, *I2 = &*RI2; + auto InstPair = std::make_pair(I1, I2); // I1 and I2 should have a single use in the same PHI node, and they // perform the same operation. // Cannot move control-flow-involving, volatile loads, vaarg, etc. @@ -1291,11 +1299,11 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { I1->mayHaveSideEffects() || I2->mayHaveSideEffects() || I1->mayReadOrWriteMemory() || I2->mayReadOrWriteMemory() || !I1->hasOneUse() || !I2->hasOneUse() || - MapValueFromBB1ToBB2.find(I1) == MapValueFromBB1ToBB2.end() || - MapValueFromBB1ToBB2[I1].first != I2) + !JointValueMap.count(InstPair)) return Changed; // Check whether we should swap the operands of ICmpInst. + // TODO: Add support of communativity. ICmpInst *ICmp1 = dyn_cast(I1), *ICmp2 = dyn_cast(I2); bool SwapOpnds = false; if (ICmp1 && ICmp2 && @@ -1316,16 +1324,13 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { // with a PHI node after sinking. We only handle the case where there is // a single pair of different operands. Value *DifferentOp1 = nullptr, *DifferentOp2 = nullptr; - unsigned Op1Idx = 0; + unsigned Op1Idx = ~0U; for (unsigned I = 0, E = I1->getNumOperands(); I != E; ++I) { if (I1->getOperand(I) == I2->getOperand(I)) continue; - // Early exit if we have more-than one pair of different operands or - // the different operand is already in MapValueFromBB1ToBB2. - // Early exit if we need a PHI node to replace a constant. - if (DifferentOp1 || - MapValueFromBB1ToBB2.find(I1->getOperand(I)) != - MapValueFromBB1ToBB2.end() || + // Early exit if we have more-than one pair of different operands or if + // we need a PHI node to replace a constant. + if (Op1Idx != ~0U || isa(I1->getOperand(I)) || isa(I2->getOperand(I))) { // If we can't sink the instructions, undo the swapping. @@ -1338,24 +1343,27 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { DifferentOp2 = I2->getOperand(I); } - // We insert the pair of different operands to MapValueFromBB1ToBB2 and - // remove (I1, I2) from MapValueFromBB1ToBB2. - if (DifferentOp1) { - PHINode *NewPN = PHINode::Create(DifferentOp1->getType(), 2, - DifferentOp1->getName() + ".sink", - BBEnd->begin()); - MapValueFromBB1ToBB2[DifferentOp1] = std::make_pair(DifferentOp2, NewPN); + DEBUG(dbgs() << "SINK common instructions " << *I1 << "\n"); + DEBUG(dbgs() << " " << *I2 << "\n"); + + // We insert the pair of different operands to JointValueMap and + // remove (I1, I2) from JointValueMap. + if (Op1Idx != ~0U) { + auto &NewPN = JointValueMap[std::make_pair(DifferentOp1, DifferentOp2)]; + if (!NewPN) { + NewPN = + PHINode::Create(DifferentOp1->getType(), 2, + DifferentOp1->getName() + ".sink", BBEnd->begin()); + NewPN->addIncoming(DifferentOp1, BB1); + NewPN->addIncoming(DifferentOp2, BB2); + DEBUG(dbgs() << "Create PHI node " << *NewPN << "\n";); + } // I1 should use NewPN instead of DifferentOp1. I1->setOperand(Op1Idx, NewPN); - NewPN->addIncoming(DifferentOp1, BB1); - NewPN->addIncoming(DifferentOp2, BB2); - DEBUG(dbgs() << "Create PHI node " << *NewPN << "\n";); } - PHINode *OldPN = MapValueFromBB1ToBB2[I1].second; - MapValueFromBB1ToBB2.erase(I1); + PHINode *OldPN = JointValueMap[InstPair]; + JointValueMap.erase(InstPair); - DEBUG(dbgs() << "SINK common instructions " << *I1 << "\n";); - DEBUG(dbgs() << " " << *I2 << "\n";); // We need to update RE1 and RE2 if we are going to sink the first // instruction in the basic block down. bool UpdateRE1 = (I1 == BB1->begin()), UpdateRE2 = (I2 == BB2->begin()); @@ -2028,8 +2036,10 @@ static bool ExtractBranchMetadata(BranchInst *BI, "Looking for probabilities on unconditional branch?"); MDNode *ProfileData = BI->getMetadata(LLVMContext::MD_prof); if (!ProfileData || ProfileData->getNumOperands() != 3) return false; - ConstantInt *CITrue = dyn_cast(ProfileData->getOperand(1)); - ConstantInt *CIFalse = dyn_cast(ProfileData->getOperand(2)); + ConstantInt *CITrue = + mdconst::dyn_extract(ProfileData->getOperand(1)); + ConstantInt *CIFalse = + mdconst::dyn_extract(ProfileData->getOperand(2)); if (!CITrue || !CIFalse) return false; ProbTrue = CITrue->getValue().getZExtValue(); ProbFalse = CIFalse->getValue().getZExtValue(); @@ -2710,7 +2720,7 @@ static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { /// the PHI, merging the third icmp into the switch. static bool TryToSimplifyUncondBranchWithICmpInIt( ICmpInst *ICI, IRBuilder<> &Builder, const TargetTransformInfo &TTI, - unsigned BonusInstThreshold, const DataLayout *DL, AssumptionTracker *AT) { + unsigned BonusInstThreshold, const DataLayout *DL, AssumptionCache *AC) { BasicBlock *BB = ICI->getParent(); // If the block has any PHIs in it or the icmp has multiple uses, it is too @@ -2743,7 +2753,7 @@ static bool TryToSimplifyUncondBranchWithICmpInIt( ICI->eraseFromParent(); } // BB is now empty, so it is likely to simplify away. - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } // Ok, the block is reachable from the default dest. If the constant we're @@ -2759,7 +2769,7 @@ static bool TryToSimplifyUncondBranchWithICmpInIt( ICI->replaceAllUsesWith(V); ICI->eraseFromParent(); // BB is now empty, so it is likely to simplify away. - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } // The use of the icmp has to be in the 'end' block, by the only PHI node in @@ -2825,7 +2835,7 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const DataLayout *DL, // 'setne's and'ed together, collect them. // Try to gather values from a chain of and/or to be turned into a switch - ConstantComparesGatherer ConstantCompare{Cond, DL}; + ConstantComparesGatherer ConstantCompare(Cond, DL); // Unpack the result SmallVectorImpl &Values = ConstantCompare.Vals; Value *CompVal = ConstantCompare.CompValue; @@ -2939,20 +2949,9 @@ bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) { return false; // Turn all invokes that unwind here into calls and delete the basic block. - bool InvokeRequiresTableEntry = false; - bool Changed = false; for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) { InvokeInst *II = cast((*PI++)->getTerminator()); - - if (II->hasFnAttr(Attribute::UWTable)) { - // Don't remove an `invoke' instruction if the ABI requires an entry into - // the table. - InvokeRequiresTableEntry = true; - continue; - } - SmallVector Args(II->op_begin(), II->op_end() - 3); - // Insert a call instruction before the invoke. CallInst *Call = CallInst::Create(II->getCalledValue(), Args, "", II); Call->takeName(II); @@ -2972,14 +2971,11 @@ bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) { // Finally, delete the invoke instruction! II->eraseFromParent(); - Changed = true; } - if (!InvokeRequiresTableEntry) - // The landingpad is now unreachable. Zap it. - BB->eraseFromParent(); - - return Changed; + // The landingpad is now unreachable. Zap it. + BB->eraseFromParent(); + return true; } bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) { @@ -3010,7 +3006,7 @@ bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) { } // If we eliminated all predecessors of the block, delete the block now. - if (pred_begin(BB) == pred_end(BB)) + if (pred_empty(BB)) // We know there are no successors, so just nuke the block. BB->eraseFromParent(); @@ -3111,55 +3107,6 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { --i; --e; Changed = true; } - // If the default value is unreachable, figure out the most popular - // destination and make it the default. - if (SI->getDefaultDest() == BB) { - std::map > Popularity; - for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); - i != e; ++i) { - std::pair &entry = - Popularity[i.getCaseSuccessor()]; - if (entry.first == 0) { - entry.first = 1; - entry.second = i.getCaseIndex(); - } else { - entry.first++; - } - } - - // Find the most popular block. - unsigned MaxPop = 0; - unsigned MaxIndex = 0; - BasicBlock *MaxBlock = nullptr; - for (std::map >::iterator - I = Popularity.begin(), E = Popularity.end(); I != E; ++I) { - if (I->second.first > MaxPop || - (I->second.first == MaxPop && MaxIndex > I->second.second)) { - MaxPop = I->second.first; - MaxIndex = I->second.second; - MaxBlock = I->first; - } - } - if (MaxBlock) { - // Make this the new default, allowing us to delete any explicit - // edges to it. - SI->setDefaultDest(MaxBlock); - Changed = true; - - // If MaxBlock has phinodes in it, remove MaxPop-1 entries from - // it. - if (isa(MaxBlock->begin())) - for (unsigned i = 0; i != MaxPop-1; ++i) - MaxBlock->removePredecessor(SI->getParent()); - - for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); - i != e; ++i) - if (i.getCaseSuccessor() == MaxBlock) { - SI->removeCase(i); - --i; --e; - } - } - } } else if (InvokeInst *II = dyn_cast(TI)) { if (II->getUnwindDest() == BB) { // Convert the invoke to a call instruction. This would be a good @@ -3183,7 +3130,7 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { } // If this block is now dead, remove it. - if (pred_begin(BB) == pred_end(BB) && + if (pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()) { // We know there are no successors, so just nuke the block. BB->eraseFromParent(); @@ -3193,70 +3140,122 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { return Changed; } -/// TurnSwitchRangeIntoICmp - Turns a switch with that contains only a -/// integer range comparison into a sub, an icmp and a branch. -static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) { - assert(SI->getNumCases() > 1 && "Degenerate switch?"); +static bool CasesAreContiguous(SmallVectorImpl &Cases) { + assert(Cases.size() >= 1); - // Make sure all cases point to the same destination and gather the values. - SmallVector Cases; - SwitchInst::CaseIt I = SI->case_begin(); - Cases.push_back(I.getCaseValue()); - SwitchInst::CaseIt PrevI = I++; - for (SwitchInst::CaseIt E = SI->case_end(); I != E; PrevI = I++) { - if (PrevI.getCaseSuccessor() != I.getCaseSuccessor()) + array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate); + for (size_t I = 1, E = Cases.size(); I != E; ++I) { + if (Cases[I - 1]->getValue() != Cases[I]->getValue() + 1) return false; - Cases.push_back(I.getCaseValue()); } - assert(Cases.size() == SI->getNumCases() && "Not all cases gathered"); + return true; +} - // Sort the case values, then check if they form a range we can transform. - array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate); - for (unsigned I = 1, E = Cases.size(); I != E; ++I) { - if (Cases[I-1]->getValue() != Cases[I]->getValue()+1) - return false; +/// Turn a switch with two reachable destinations into an integer range +/// comparison and branch. +static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) { + assert(SI->getNumCases() > 1 && "Degenerate switch?"); + + bool HasDefault = + !isa(SI->getDefaultDest()->getFirstNonPHIOrDbg()); + + // Partition the cases into two sets with different destinations. + BasicBlock *DestA = HasDefault ? SI->getDefaultDest() : nullptr; + BasicBlock *DestB = nullptr; + SmallVector CasesA; + SmallVector CasesB; + + for (SwitchInst::CaseIt I : SI->cases()) { + BasicBlock *Dest = I.getCaseSuccessor(); + if (!DestA) DestA = Dest; + if (Dest == DestA) { + CasesA.push_back(I.getCaseValue()); + continue; + } + if (!DestB) DestB = Dest; + if (Dest == DestB) { + CasesB.push_back(I.getCaseValue()); + continue; + } + return false; // More than two destinations. } - Constant *Offset = ConstantExpr::getNeg(Cases.back()); - Constant *NumCases = ConstantInt::get(Offset->getType(), SI->getNumCases()); + assert(DestA && DestB && "Single-destination switch should have been folded."); + assert(DestA != DestB); + assert(DestB != SI->getDefaultDest()); + assert(!CasesB.empty() && "There must be non-default cases."); + assert(!CasesA.empty() || HasDefault); + + // Figure out if one of the sets of cases form a contiguous range. + SmallVectorImpl *ContiguousCases = nullptr; + BasicBlock *ContiguousDest = nullptr; + BasicBlock *OtherDest = nullptr; + if (!CasesA.empty() && CasesAreContiguous(CasesA)) { + ContiguousCases = &CasesA; + ContiguousDest = DestA; + OtherDest = DestB; + } else if (CasesAreContiguous(CasesB)) { + ContiguousCases = &CasesB; + ContiguousDest = DestB; + OtherDest = DestA; + } else + return false; + + // Start building the compare and branch. + + Constant *Offset = ConstantExpr::getNeg(ContiguousCases->back()); + Constant *NumCases = ConstantInt::get(Offset->getType(), ContiguousCases->size()); Value *Sub = SI->getCondition(); if (!Offset->isNullValue()) - Sub = Builder.CreateAdd(Sub, Offset, Sub->getName()+".off"); + Sub = Builder.CreateAdd(Sub, Offset, Sub->getName() + ".off"); + Value *Cmp; // If NumCases overflowed, then all possible values jump to the successor. - if (NumCases->isNullValue() && SI->getNumCases() != 0) + if (NumCases->isNullValue() && !ContiguousCases->empty()) Cmp = ConstantInt::getTrue(SI->getContext()); else Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch"); - BranchInst *NewBI = Builder.CreateCondBr( - Cmp, SI->case_begin().getCaseSuccessor(), SI->getDefaultDest()); + BranchInst *NewBI = Builder.CreateCondBr(Cmp, ContiguousDest, OtherDest); // Update weight for the newly-created conditional branch. - SmallVector Weights; - bool HasWeights = HasBranchWeights(SI); - if (HasWeights) { + if (HasBranchWeights(SI)) { + SmallVector Weights; GetBranchWeights(SI, Weights); if (Weights.size() == 1 + SI->getNumCases()) { - // Combine all weights for the cases to be the true weight of NewBI. - // We assume that the sum of all weights for a Terminator can fit into 32 - // bits. - uint32_t NewTrueWeight = 0; - for (unsigned I = 1, E = Weights.size(); I != E; ++I) - NewTrueWeight += (uint32_t)Weights[I]; + uint64_t TrueWeight = 0; + uint64_t FalseWeight = 0; + for (size_t I = 0, E = Weights.size(); I != E; ++I) { + if (SI->getSuccessor(I) == ContiguousDest) + TrueWeight += Weights[I]; + else + FalseWeight += Weights[I]; + } + while (TrueWeight > UINT32_MAX || FalseWeight > UINT32_MAX) { + TrueWeight /= 2; + FalseWeight /= 2; + } NewBI->setMetadata(LLVMContext::MD_prof, - MDBuilder(SI->getContext()). - createBranchWeights(NewTrueWeight, - (uint32_t)Weights[0])); + MDBuilder(SI->getContext()).createBranchWeights( + (uint32_t)TrueWeight, (uint32_t)FalseWeight)); } } - // Prune obsolete incoming values off the successor's PHI nodes. - for (BasicBlock::iterator BBI = SI->case_begin().getCaseSuccessor()->begin(); - isa(BBI); ++BBI) { - for (unsigned I = 0, E = SI->getNumCases()-1; I != E; ++I) + // Prune obsolete incoming values off the successors' PHI nodes. + for (auto BBI = ContiguousDest->begin(); isa(BBI); ++BBI) { + unsigned PreviousEdges = ContiguousCases->size(); + if (ContiguousDest == SI->getDefaultDest()) ++PreviousEdges; + for (unsigned I = 0, E = PreviousEdges - 1; I != E; ++I) cast(BBI)->removeIncomingValue(SI->getParent()); } + for (auto BBI = OtherDest->begin(); isa(BBI); ++BBI) { + unsigned PreviousEdges = SI->getNumCases() - ContiguousCases->size(); + if (OtherDest == SI->getDefaultDest()) ++PreviousEdges; + for (unsigned I = 0, E = PreviousEdges - 1; I != E; ++I) + cast(BBI)->removeIncomingValue(SI->getParent()); + } + + // Drop the switch. SI->eraseFromParent(); return true; @@ -3265,11 +3264,11 @@ static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) { /// EliminateDeadSwitchCases - Compute masked bits for the condition of a switch /// and use it to remove dead cases. static bool EliminateDeadSwitchCases(SwitchInst *SI, const DataLayout *DL, - AssumptionTracker *AT) { + AssumptionCache *AC) { Value *Cond = SI->getCondition(); unsigned Bits = Cond->getType()->getIntegerBitWidth(); APInt KnownZero(Bits, 0), KnownOne(Bits, 0); - computeKnownBits(Cond, KnownZero, KnownOne, DL, 0, AT, SI); + computeKnownBits(Cond, KnownZero, KnownOne, DL, 0, AC, SI); // Gather dead cases. SmallVector DeadCases; @@ -3476,6 +3475,21 @@ GetCaseResults(SwitchInst *SI, continue; } else if (Constant *C = ConstantFold(I, ConstantPool, DL)) { // Instruction is side-effect free and constant. + + // If the instruction has uses outside this block or a phi node slot for + // the block, it is not safe to bypass the instruction since it would then + // no longer dominate all its uses. + for (auto &Use : I->uses()) { + User *User = Use.getUser(); + if (Instruction *I = dyn_cast(User)) + if (I->getParent() == CaseDest) + continue; + if (PHINode *Phi = dyn_cast(User)) + if (Phi->getIncomingBlock(Use) == CaseDest) + continue; + return false; + } + ConstantPool.insert(std::make_pair(I, C)); } else { break; @@ -3501,12 +3515,6 @@ GetCaseResults(SwitchInst *SI, if (!ConstVal) return false; - // Note: If the constant comes from constant-propagating the case value - // through the CaseDest basic block, it will be safe to remove the - // instructions in that block. They cannot be used (except in the phi nodes - // we visit) outside CaseDest, because that block does not dominate its - // successor. If it did, we would not be in this phi node. - // Be conservative about which kinds of constants we support. if (!ValidLookupTableConstant(ConstVal)) return false; @@ -3647,7 +3655,7 @@ static void RemoveSwitchAfterSelectConversion(SwitchInst *SI, PHINode *PHI, /// phi nodes in a common successor block with only two different /// constant values, replace the switch with select. static bool SwitchToSelect(SwitchInst *SI, IRBuilder<> &Builder, - const DataLayout *DL, AssumptionTracker *AT) { + const DataLayout *DL, AssumptionCache *AC) { Value *const Cond = SI->getCondition(); PHINode *PHI = nullptr; BasicBlock *CommonDest = nullptr; @@ -3974,6 +3982,89 @@ static bool ShouldBuildLookupTable(SwitchInst *SI, return SI->getNumCases() * 10 >= TableSize * 4; } +/// Try to reuse the switch table index compare. Following pattern: +/// \code +/// if (idx < tablesize) +/// r = table[idx]; // table does not contain default_value +/// else +/// r = default_value; +/// if (r != default_value) +/// ... +/// \endcode +/// Is optimized to: +/// \code +/// cond = idx < tablesize; +/// if (cond) +/// r = table[idx]; +/// else +/// r = default_value; +/// if (cond) +/// ... +/// \endcode +/// Jump threading will then eliminate the second if(cond). +static void reuseTableCompare(User *PhiUser, BasicBlock *PhiBlock, + BranchInst *RangeCheckBranch, Constant *DefaultValue, + const SmallVectorImpl >& Values) { + + ICmpInst *CmpInst = dyn_cast(PhiUser); + if (!CmpInst) + return; + + // We require that the compare is in the same block as the phi so that jump + // threading can do its work afterwards. + if (CmpInst->getParent() != PhiBlock) + return; + + Constant *CmpOp1 = dyn_cast(CmpInst->getOperand(1)); + if (!CmpOp1) + return; + + Value *RangeCmp = RangeCheckBranch->getCondition(); + Constant *TrueConst = ConstantInt::getTrue(RangeCmp->getType()); + Constant *FalseConst = ConstantInt::getFalse(RangeCmp->getType()); + + // Check if the compare with the default value is constant true or false. + Constant *DefaultConst = ConstantExpr::getICmp(CmpInst->getPredicate(), + DefaultValue, CmpOp1, true); + if (DefaultConst != TrueConst && DefaultConst != FalseConst) + return; + + // Check if the compare with the case values is distinct from the default + // compare result. + for (auto ValuePair : Values) { + Constant *CaseConst = ConstantExpr::getICmp(CmpInst->getPredicate(), + ValuePair.second, CmpOp1, true); + if (!CaseConst || CaseConst == DefaultConst) + return; + assert((CaseConst == TrueConst || CaseConst == FalseConst) && + "Expect true or false as compare result."); + } + + // Check if the branch instruction dominates the phi node. It's a simple + // dominance check, but sufficient for our needs. + // Although this check is invariant in the calling loops, it's better to do it + // at this late stage. Practically we do it at most once for a switch. + BasicBlock *BranchBlock = RangeCheckBranch->getParent(); + for (auto PI = pred_begin(PhiBlock), E = pred_end(PhiBlock); PI != E; ++PI) { + BasicBlock *Pred = *PI; + if (Pred != BranchBlock && Pred->getUniquePredecessor() != BranchBlock) + return; + } + + if (DefaultConst == FalseConst) { + // The compare yields the same result. We can replace it. + CmpInst->replaceAllUsesWith(RangeCmp); + ++NumTableCmpReuses; + } else { + // The compare yields the same result, just inverted. We can replace it. + Value *InvertedTableCmp = BinaryOperator::CreateXor(RangeCmp, + ConstantInt::get(RangeCmp->getType(), 1), "inverted.cmp", + RangeCheckBranch); + CmpInst->replaceAllUsesWith(InvertedTableCmp); + ++NumTableCmpReuses; + } +} + /// SwitchToLookupTable - If the switch is only used to initialize one or more /// phi nodes in a common successor block with different constant values, /// replace the switch with lookup tables. @@ -4050,11 +4141,8 @@ static bool SwitchToLookupTable(SwitchInst *SI, // If the table has holes, we need a constant result for the default case // or a bitmask that fits in a register. SmallVector, 4> DefaultResultsList; - bool HasDefaultResults = false; - if (TableHasHoles) { - HasDefaultResults = GetCaseResults(SI, nullptr, SI->getDefaultDest(), + bool HasDefaultResults = GetCaseResults(SI, nullptr, SI->getDefaultDest(), &CommonDest, DefaultResultsList, DL); - } bool NeedMask = (TableHasHoles && !HasDefaultResults); if (NeedMask) { @@ -4098,6 +4186,8 @@ static bool SwitchToLookupTable(SwitchInst *SI, // lookup table BB. Otherwise, check if the condition value is within the case // range. If it is so, branch to the new BB. Otherwise branch to SI's default // destination. + BranchInst *RangeCheckBranch = nullptr; + const bool GeneratingCoveredLookupTable = MaxTableSize == TableSize; if (GeneratingCoveredLookupTable) { Builder.CreateBr(LookupBB); @@ -4108,7 +4198,7 @@ static bool SwitchToLookupTable(SwitchInst *SI, } else { Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get( MinCaseVal->getType(), TableSize)); - Builder.CreateCondBr(Cmp, LookupBB, SI->getDefaultDest()); + RangeCheckBranch = Builder.CreateCondBr(Cmp, LookupBB, SI->getDefaultDest()); } // Populate the BB that does the lookups. @@ -4159,11 +4249,11 @@ static bool SwitchToLookupTable(SwitchInst *SI, bool ReturnedEarly = false; for (size_t I = 0, E = PHIs.size(); I != E; ++I) { PHINode *PHI = PHIs[I]; + const ResultListTy &ResultList = ResultLists[PHI]; // If using a bitmask, use any value to fill the lookup table holes. Constant *DV = NeedMask ? ResultLists[PHI][0].second : DefaultResults[PHI]; - SwitchLookupTable Table(Mod, TableSize, MinCaseVal, ResultLists[PHI], - DV, DL); + SwitchLookupTable Table(Mod, TableSize, MinCaseVal, ResultList, DV, DL); Value *Result = Table.BuildLookup(TableIndex, Builder); @@ -4176,6 +4266,16 @@ static bool SwitchToLookupTable(SwitchInst *SI, break; } + // Do a small peephole optimization: re-use the switch table compare if + // possible. + if (!TableHasHoles && HasDefaultResults && RangeCheckBranch) { + BasicBlock *PhiBlock = PHI->getParent(); + // Search for compare instructions which use the phi. + for (auto *User : PHI->users()) { + reuseTableCompare(User, PhiBlock, RangeCheckBranch, DV, ResultList); + } + } + PHI->addIncoming(Result, LookupBB); } @@ -4206,12 +4306,12 @@ bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) { // see if that predecessor totally determines the outcome of this switch. if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; Value *Cond = SI->getCondition(); if (SelectInst *Select = dyn_cast(Cond)) if (SimplifySwitchOnSelect(SI, Select)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; // If the block only contains the switch, see if we can fold the block // away into any preds. @@ -4221,25 +4321,25 @@ bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) { ++BBI; if (SI == &*BBI) if (FoldValueComparisonIntoPredecessors(SI, Builder)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } // Try to transform the switch into an icmp and a branch. if (TurnSwitchRangeIntoICmp(SI, Builder)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; // Remove unreachable cases. - if (EliminateDeadSwitchCases(SI, DL, AT)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + if (EliminateDeadSwitchCases(SI, DL, AC)) + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; - if (SwitchToSelect(SI, Builder, DL, AT)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + if (SwitchToSelect(SI, Builder, DL, AC)) + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; if (ForwardSwitchConditionToPHI(SI)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; if (SwitchToLookupTable(SI, Builder, TTI, DL)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; return false; } @@ -4276,7 +4376,7 @@ bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { if (SelectInst *SI = dyn_cast(IBI->getAddress())) { if (SimplifyIndirectBrOnSelect(IBI, SI)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } return Changed; } @@ -4301,7 +4401,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){ ; if (I->isTerminator() && TryToSimplifyUncondBranchWithICmpInIt(ICI, Builder, TTI, - BonusInstThreshold, DL, AT)) + BonusInstThreshold, DL, AC)) return true; } @@ -4310,7 +4410,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){ // predecessor and use logical operations to update the incoming value // for PHI nodes in common successor. if (FoldBranchToCommonDest(BI, DL, BonusInstThreshold)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; return false; } @@ -4325,7 +4425,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { // switch. if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; // This block must be empty, except for the setcond inst, if it exists. // Ignore dbg intrinsics. @@ -4335,14 +4435,14 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { ++I; if (&*I == BI) { if (FoldValueComparisonIntoPredecessors(BI, Builder)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } else if (&*I == cast(BI->getCondition())){ ++I; // Ignore dbg intrinsics. while (isa(I)) ++I; if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } } @@ -4354,7 +4454,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { // branches to us and one of our successors, fold the comparison into the // predecessor and use logical operations to pick the right destination. if (FoldBranchToCommonDest(BI, DL, BonusInstThreshold)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; // We have a conditional branch to two blocks that are only reachable // from BI. We know that the condbr dominates the two blocks, so see if @@ -4363,7 +4463,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (BI->getSuccessor(0)->getSinglePredecessor()) { if (BI->getSuccessor(1)->getSinglePredecessor()) { if (HoistThenElseCodeToIf(BI, DL)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } else { // If Successor #1 has multiple preds, we may be able to conditionally // execute Successor #0 if it branches to Successor #1. @@ -4371,7 +4471,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (Succ0TI->getNumSuccessors() == 1 && Succ0TI->getSuccessor(0) == BI->getSuccessor(1)) if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0), DL)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } } else if (BI->getSuccessor(1)->getSinglePredecessor()) { // If Successor #0 has multiple preds, we may be able to conditionally @@ -4380,7 +4480,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (Succ1TI->getNumSuccessors() == 1 && Succ1TI->getSuccessor(0) == BI->getSuccessor(0)) if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1), DL)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; } // If this is a branch on a phi node in the current block, thread control @@ -4388,14 +4488,14 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (PHINode *PN = dyn_cast(BI->getCondition())) if (PN->getParent() == BI->getParent()) if (FoldCondBranchOnPHI(BI, DL)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; // Scan predecessor blocks for conditional branches. for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) if (BranchInst *PBI = dyn_cast((*PI)->getTerminator())) if (PBI != BI && PBI->isConditional()) if (SimplifyCondBranchToCondBranch(PBI, BI)) - return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AT) | true; + return SimplifyCFG(BB, TTI, BonusInstThreshold, DL, AC) | true; return false; } @@ -4476,7 +4576,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) { // Remove basic blocks that have no predecessors (except the entry block)... // or that just have themself as a predecessor. These are unreachable. - if ((pred_begin(BB) == pred_end(BB) && + if ((pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()) || BB->getSinglePredecessor() == BB) { DEBUG(dbgs() << "Removing BB: \n" << *BB); @@ -4539,7 +4639,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) { /// of the CFG. It returns true if a modification was made. /// bool llvm::SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI, - unsigned BonusInstThreshold, - const DataLayout *DL, AssumptionTracker *AT) { - return SimplifyCFGOpt(TTI, BonusInstThreshold, DL, AT).run(BB); + unsigned BonusInstThreshold, const DataLayout *DL, + AssumptionCache *AC) { + return SimplifyCFGOpt(TTI, BonusInstThreshold, DL, AC).run(BB); }