X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FUtils%2FSimplifyCFG.cpp;h=5f55b89b0f90f78ed92f2f2bc42247097b5f7a4c;hb=dad20b2ae2544708d6a33abdb9bddd0a329f50e0;hp=0dde18522f489055a1a08ede8f596f215257c816;hpb=5c98f14b787e476636196939eb4dbfcce8615906;p=oota-llvm.git diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 0dde18522f4..5f55b89b0f9 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -70,8 +70,10 @@ static cl::opt HoistCondStores( cl::desc("Hoist conditional stores if an unconditional store precedes")); 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"); @@ -356,114 +358,177 @@ static ConstantInt *GetConstantInt(Value *V, const DataLayout *DL) { return nullptr; } -/// GatherConstantCompares - Given a potentially 'or'd or 'and'd together -/// collection of icmp eq/ne instructions that compare a value against a -/// constant, return the value being compared, and stick the constant into the -/// Values vector. -static Value * -GatherConstantCompares(Value *V, std::vector &Vals, Value *&Extra, - const DataLayout *DL, bool isEQ, unsigned &UsedICmps) { - Instruction *I = dyn_cast(V); - if (!I) return nullptr; - - // If this is an icmp against a constant, handle this as one of the cases. - if (ICmpInst *ICI = dyn_cast(I)) { - if (ConstantInt *C = GetConstantInt(I->getOperand(1), DL)) { - Value *RHSVal; - ConstantInt *RHSC; - - if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) { - // (x & ~2^x) == y --> x == y || x == y|2^x - // This undoes a transformation done by instcombine to fuse 2 compares. - if (match(ICI->getOperand(0), - m_And(m_Value(RHSVal), m_ConstantInt(RHSC)))) { - APInt Not = ~RHSC->getValue(); - if (Not.isPowerOf2()) { - Vals.push_back(C); - Vals.push_back( - ConstantInt::get(C->getContext(), C->getValue() | Not)); - UsedICmps++; - return RHSVal; - } - } +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. +/// It will depth-first traverse the chain of comparison, seeking for patterns +/// like %a == 12 or %a < 4 and combine them to produce a set of integer +/// representing the different cases for the switch. +/// Note that if the chain is composed of '||' it will build the set of elements +/// that matches the comparisons (i.e. any of this value validate the chain) +/// while for a chain of '&&' it will build the set elements that make the test +/// fail. +struct ConstantComparesGatherer { + + 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) + : CompValue(nullptr), Extra(nullptr), UsedICmps(0) { + gather(Cond, DL); + } + + /// Prevent copy + ConstantComparesGatherer(const ConstantComparesGatherer &) + LLVM_DELETED_FUNCTION; + ConstantComparesGatherer & + operator=(const ConstantComparesGatherer &) LLVM_DELETED_FUNCTION; + +private: - UsedICmps++; - Vals.push_back(C); - return I->getOperand(0); + /// Try to set the current value used for the comparison, it succeeds only if + /// 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; + CompValue = NewVal; + return (CompValue != nullptr); + } + + /// Try to match Instruction "I" as a comparison against a constant and + /// populates the array Vals with the set of values that match (or do not + /// match depending on isEQ). + /// Return false on failure. On success, the Value the comparison matched + /// against is placed in CompValue. + /// If CompValue is already set, the function is expected to fail if a match + /// is found but the value compared to is different. + bool matchInstruction(Instruction *I, const DataLayout *DL, bool isEQ) { + // If this is an icmp against a constant, handle this as one of the cases. + ICmpInst *ICI; + ConstantInt *C; + if (!((ICI = dyn_cast(I)) && + (C = GetConstantInt(I->getOperand(1), DL)))) { + return false; + } + + Value *RHSVal; + ConstantInt *RHSC; + + // Pattern match a special case + // (x & ~2^x) == y --> x == y || x == y|2^x + // This undoes a transformation done by instcombine to fuse 2 compares. + if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) { + if (match(ICI->getOperand(0), + m_And(m_Value(RHSVal), m_ConstantInt(RHSC)))) { + APInt Not = ~RHSC->getValue(); + if (Not.isPowerOf2()) { + // If we already have a value for the switch, it has to match! + if(!setValueOnce(RHSVal)) + return false; + + Vals.push_back(C); + Vals.push_back(ConstantInt::get(C->getContext(), + C->getValue() | Not)); + UsedICmps++; + return true; + } } - // If we have "x ult 3" comparison, for example, then we can add 0,1,2 to - // the set. - ConstantRange Span = - ConstantRange::makeICmpRegion(ICI->getPredicate(), C->getValue()); - - // Shift the range if the compare is fed by an add. This is the range - // compare idiom as emitted by instcombine. - bool hasAdd = - match(I->getOperand(0), m_Add(m_Value(RHSVal), m_ConstantInt(RHSC))); - if (hasAdd) - Span = Span.subtract(RHSC->getValue()); - - // If this is an and/!= check then we want to optimize "x ugt 2" into - // x != 0 && x != 1. - if (!isEQ) - Span = Span.inverse(); - - // If there are a ton of values, we don't want to make a ginormous switch. - if (Span.getSetSize().ugt(8) || Span.isEmptySet()) - return nullptr; - - for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp) - Vals.push_back(ConstantInt::get(V->getContext(), Tmp)); + // If we already have a value for the switch, it has to match! + if(!setValueOnce(ICI->getOperand(0))) + return false; + UsedICmps++; - return hasAdd ? RHSVal : I->getOperand(0); + Vals.push_back(C); + return ICI->getOperand(0); } - return nullptr; - } - // Otherwise, we can only handle an | or &, depending on isEQ. - if (I->getOpcode() != (isEQ ? Instruction::Or : Instruction::And)) - return nullptr; + // If we have "x ult 3", for example, then we can add 0,1,2 to the set. + ConstantRange Span = ConstantRange::makeICmpRegion(ICI->getPredicate(), + C->getValue()); - unsigned NumValsBeforeLHS = Vals.size(); - unsigned UsedICmpsBeforeLHS = UsedICmps; - if (Value *LHS = GatherConstantCompares(I->getOperand(0), Vals, Extra, DL, - isEQ, UsedICmps)) { - unsigned NumVals = Vals.size(); - unsigned UsedICmpsBeforeRHS = UsedICmps; - if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, DL, - isEQ, UsedICmps)) { - if (LHS == RHS) - return LHS; - Vals.resize(NumVals); - UsedICmps = UsedICmpsBeforeRHS; + // Shift the range if the compare is fed by an add. This is the range + // compare idiom as emitted by instcombine. + Value *CandidateVal = I->getOperand(0); + if(match(I->getOperand(0), m_Add(m_Value(RHSVal), m_ConstantInt(RHSC)))) { + Span = Span.subtract(RHSC->getValue()); + CandidateVal = RHSVal; } - // The RHS of the or/and can't be folded in and we haven't used "Extra" yet, - // set it and return success. - if (Extra == nullptr || Extra == I->getOperand(1)) { - Extra = I->getOperand(1); - return LHS; + // If this is an and/!= check, then we are looking to build the set of + // value that *don't* pass the and chain. I.e. to turn "x ugt 2" into + // x != 0 && x != 1. + if (!isEQ) + Span = Span.inverse(); + + // If there are a ton of values, we don't want to make a ginormous switch. + if (Span.getSetSize().ugt(8) || Span.isEmptySet()) { + return false; } - Vals.resize(NumValsBeforeLHS); - UsedICmps = UsedICmpsBeforeLHS; - return nullptr; + // If we already have a value for the switch, it has to match! + if(!setValueOnce(CandidateVal)) + return false; + + // Add all values from the range to the set + for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp) + Vals.push_back(ConstantInt::get(I->getContext(), Tmp)); + + UsedICmps++; + return true; + } - // If the LHS can't be folded in, but Extra is available and RHS can, try to - // use LHS as Extra. - if (Extra == nullptr || Extra == I->getOperand(0)) { - Value *OldExtra = Extra; - Extra = I->getOperand(0); - if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, DL, - isEQ, UsedICmps)) - return RHS; - assert(Vals.size() == NumValsBeforeLHS); - Extra = OldExtra; + /// gather - Given a potentially 'or'd or 'and'd together collection of icmp + /// eq/ne/lt/gt instructions that compare a value against a constant, extract + /// the value being compared, and stick the list constants into the Vals + /// vector. + /// One "Extra" case is allowed to differ from the other. + void gather(Value *V, const DataLayout *DL) { + Instruction *I = dyn_cast(V); + bool isEQ = (I->getOpcode() == Instruction::Or); + + // Keep a stack (SmallVector for efficiency) for depth-first traversal + SmallVector DFT; + + // Initialize + DFT.push_back(V); + + while(!DFT.empty()) { + V = DFT.pop_back_val(); + + if (Instruction *I = dyn_cast(V)) { + // If it is a || (or && depending on isEQ), process the operands. + if (I->getOpcode() == (isEQ ? Instruction::Or : Instruction::And)) { + DFT.push_back(I->getOperand(1)); + DFT.push_back(I->getOperand(0)); + continue; + } + + // Try to match the current instruction + if (matchInstruction(I, DL, isEQ)) + // Match succeed, continue the loop + continue; + } + + // One element of the sequence of || (or &&) could not be match as a + // comparison against the same value as the others. + // We allow only one "Extra" case to be checked before the switch + if (!Extra) { + Extra = V; + continue; + } + // Failed to parse a proper sequence, abort now + CompValue = nullptr; + break; + } } +}; - return nullptr; } static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) { @@ -643,13 +708,12 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, // Collect branch weights into a vector. SmallVector Weights; - MDNode* MD = SI->getMetadata(LLVMContext::MD_prof); + MDNode *MD = SI->getMetadata(LLVMContext::MD_prof); bool HasWeight = MD && (MD->getNumOperands() == 2 + SI->getNumCases()); 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;) { @@ -738,7 +802,7 @@ static int ConstantIntSortPredicate(ConstantInt *const *P1, } static inline bool HasBranchWeights(const Instruction* I) { - MDNode* ProfMD = I->getMetadata(LLVMContext::MD_prof); + MDNode *ProfMD = I->getMetadata(LLVMContext::MD_prof); if (ProfMD && ProfMD->getOperand(0)) if (MDString* MDS = dyn_cast(ProfMD->getOperand(0))) return MDS->getString().equals("branch_weights"); @@ -751,10 +815,10 @@ static inline bool HasBranchWeights(const Instruction* I) { /// metadata. static void GetBranchWeights(TerminatorInst *TI, SmallVectorImpl &Weights) { - MDNode* MD = TI->getMetadata(LLVMContext::MD_prof); + 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()); } @@ -1010,6 +1074,8 @@ static bool isSafeToHoistInvoke(BasicBlock *BB1, BasicBlock *BB2, return true; } +static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I); + /// HoistThenElseCodeToIf - Given a conditional branch that goes to BB1 and /// BB2, hoist any common code in the two blocks up into the branch block. The /// caller of this function guarantees that BI's block dominates BB1 and BB2. @@ -1059,7 +1125,8 @@ static bool HoistThenElseCodeToIf(BranchInst *BI, const DataLayout *DL) { LLVMContext::MD_tbaa, LLVMContext::MD_range, LLVMContext::MD_fpmath, - LLVMContext::MD_invariant_load + LLVMContext::MD_invariant_load, + LLVMContext::MD_nonnull }; combineMetadata(I1, I2, KnownIDs); I2->eraseFromParent(); @@ -1094,6 +1161,12 @@ HoistTerminator: if (BB1V == BB2V) continue; + // Check for passingValueIsAlwaysUndefined here because we would rather + // eliminate undefined control flow then converting it to a select. + if (passingValueIsAlwaysUndefined(BB1V, PN) || + passingValueIsAlwaysUndefined(BB2V, PN)) + return Changed; + if (isa(BB1V) && !isSafeToSpeculativelyExecute(BB1V, DL)) return Changed; if (isa(BB2V) && !isSafeToSpeculativelyExecute(BB2V, DL)) @@ -1303,6 +1376,8 @@ static bool SinkThenElseCodeToEnd(BranchInst *BI1) { if (!I2->use_empty()) I2->replaceAllUsesWith(I1); I1->intersectOptionalDataWith(I2); + // TODO: Use combineMetadata here to preserve what metadata we can + // (analogous to the hoisting case above). I2->eraseFromParent(); if (UpdateRE1) @@ -1508,6 +1583,11 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB, if (ThenV == OrigV) continue; + // Don't convert to selects if we could remove undefined behavior instead. + if (passingValueIsAlwaysUndefined(OrigV, PN) || + passingValueIsAlwaysUndefined(ThenV, PN)) + return false; + HaveRewritablePHIs = true; ConstantExpr *OrigCE = dyn_cast(OrigV); ConstantExpr *ThenCE = dyn_cast(ThenV); @@ -1956,8 +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(); @@ -2748,24 +2830,17 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const DataLayout *DL, Instruction *Cond = dyn_cast(BI->getCondition()); if (!Cond) return false; - // Change br (X == 0 | X == 1), T, F into a switch instruction. // If this is a bunch of seteq's or'd together, or if it's a bunch of // 'setne's and'ed together, collect them. - Value *CompVal = nullptr; - std::vector Values; - bool TrueWhenEqual = true; - Value *ExtraCase = nullptr; - unsigned UsedICmps = 0; - - if (Cond->getOpcode() == Instruction::Or) { - CompVal = GatherConstantCompares(Cond, Values, ExtraCase, DL, true, - UsedICmps); - } else if (Cond->getOpcode() == Instruction::And) { - CompVal = GatherConstantCompares(Cond, Values, ExtraCase, DL, false, - UsedICmps); - TrueWhenEqual = false; - } + + // Try to gather values from a chain of and/or to be turned into a switch + ConstantComparesGatherer ConstantCompare(Cond, DL); + // Unpack the result + SmallVectorImpl &Values = ConstantCompare.Vals; + Value *CompVal = ConstantCompare.CompValue; + unsigned UsedICmps = ConstantCompare.UsedICmps; + Value *ExtraCase = ConstantCompare.Extra; // If we didn't have a multiply compared value, fail. if (!CompVal) return false; @@ -2774,6 +2849,8 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const DataLayout *DL, if (UsedICmps <= 1) return false; + bool TrueWhenEqual = (Cond->getOpcode() == Instruction::Or); + // There might be duplicate constants in the list, which the switch // instruction can't handle, remove them now. array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate); @@ -3559,7 +3636,7 @@ static void RemoveSwitchAfterSelectConversion(SwitchInst *SI, PHINode *PHI, Value *SelectValue, IRBuilder<> &Builder) { BasicBlock *SelectBB = SI->getParent(); - if (PHI->getBasicBlockIndex(SelectBB) >= 0) + while (PHI->getBasicBlockIndex(SelectBB) >= 0) PHI->removeIncomingValue(SelectBB); PHI->addIncoming(SelectValue, SelectBB); @@ -3640,6 +3717,11 @@ namespace { // store that single value and return it for each lookup. SingleValueKind, + // For tables where there is a linear relationship between table index + // and values. We calculate the result with a simple multiplication + // and addition instead of a table lookup. + LinearMapKind, + // For small tables with integer elements, we can pack them into a bitmap // that fits into a target-legal register. Values are retrieved by // shift and mask operations. @@ -3657,6 +3739,10 @@ namespace { ConstantInt *BitMap; IntegerType *BitMapElementTy; + // For LinearMapKind, these are the constants used to derive the value. + ConstantInt *LinearOffset; + ConstantInt *LinearMultiplier; + // For ArrayKind, this is the array. GlobalVariable *Array; }; @@ -3669,7 +3755,7 @@ SwitchLookupTable::SwitchLookupTable(Module &M, Constant *DefaultValue, const DataLayout *DL) : SingleValue(nullptr), BitMap(nullptr), BitMapElementTy(nullptr), - Array(nullptr) { + LinearOffset(nullptr), LinearMultiplier(nullptr), Array(nullptr) { assert(Values.size() && "Can't build lookup table without values!"); assert(TableSize >= Values.size() && "Can't fit values in table!"); @@ -3714,6 +3800,43 @@ SwitchLookupTable::SwitchLookupTable(Module &M, return; } + // Check if we can derive the value with a linear transformation from the + // table index. + if (isa(ValueType)) { + bool LinearMappingPossible = true; + APInt PrevVal; + APInt DistToPrev; + assert(TableSize >= 2 && "Should be a SingleValue table."); + // Check if there is the same distance between two consecutive values. + for (uint64_t I = 0; I < TableSize; ++I) { + ConstantInt *ConstVal = dyn_cast(TableContents[I]); + if (!ConstVal) { + // This is an undef. We could deal with it, but undefs in lookup tables + // are very seldom. It's probably not worth the additional complexity. + LinearMappingPossible = false; + break; + } + APInt Val = ConstVal->getValue(); + if (I != 0) { + APInt Dist = Val - PrevVal; + if (I == 1) { + DistToPrev = Dist; + } else if (Dist != DistToPrev) { + LinearMappingPossible = false; + break; + } + } + PrevVal = Val; + } + if (LinearMappingPossible) { + LinearOffset = cast(TableContents[0]); + LinearMultiplier = ConstantInt::get(M.getContext(), DistToPrev); + Kind = LinearMapKind; + ++NumLinearMaps; + return; + } + } + // If the type is integer and the table fits in a register, build a bitmap. if (WouldFitInRegister(DL, TableSize, ValueType)) { IntegerType *IT = cast(ValueType); @@ -3749,6 +3872,16 @@ Value *SwitchLookupTable::BuildLookup(Value *Index, IRBuilder<> &Builder) { switch (Kind) { case SingleValueKind: return SingleValue; + case LinearMapKind: { + // Derive the result value from the input value. + Value *Result = Builder.CreateIntCast(Index, LinearMultiplier->getType(), + false, "switch.idx.cast"); + if (!LinearMultiplier->isOne()) + Result = Builder.CreateMul(Result, LinearMultiplier, "switch.idx.mult"); + if (!LinearOffset->isZero()) + Result = Builder.CreateAdd(Result, LinearOffset, "switch.offset"); + return Result; + } case BitMapKind: { // Type of the bitmap (e.g. i59). IntegerType *MapTy = BitMap->getType(); @@ -3820,9 +3953,8 @@ static bool ShouldBuildLookupTable(SwitchInst *SI, bool AllTablesFitInRegister = true; bool HasIllegalType = false; - for (SmallDenseMap::const_iterator I = ResultTypes.begin(), - E = ResultTypes.end(); I != E; ++I) { - Type *Ty = I->second; + for (const auto &I : ResultTypes) { + Type *Ty = I.second; // Saturate this flag to true. HasIllegalType = HasIllegalType || !TTI.isTypeLegal(Ty); @@ -3852,6 +3984,89 @@ 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. @@ -3906,16 +4121,17 @@ static bool SwitchToLookupTable(SwitchInst *SI, return false; // Append the result from this case to the list for each phi. - for (ResultsTy::iterator I = Results.begin(), E = Results.end(); I!=E; ++I) { - if (!ResultLists.count(I->first)) - PHIs.push_back(I->first); - ResultLists[I->first].push_back(std::make_pair(CaseVal, I->second)); + for (const auto &I : Results) { + PHINode *PHI = I.first; + Constant *Value = I.second; + if (!ResultLists.count(PHI)) + PHIs.push_back(PHI); + ResultLists[PHI].push_back(std::make_pair(CaseVal, Value)); } } // Keep track of the result types. - for (size_t I = 0, E = PHIs.size(); I != E; ++I) { - PHINode *PHI = PHIs[I]; + for (PHINode *PHI : PHIs) { ResultTypes[PHI] = ResultLists[PHI][0].second->getType(); } @@ -3927,11 +4143,9 @@ 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) { // As an extra penalty for the validity test we require more cases. @@ -3941,9 +4155,9 @@ static bool SwitchToLookupTable(SwitchInst *SI, return false; } - for (size_t I = 0, E = DefaultResultsList.size(); I != E; ++I) { - PHINode *PHI = DefaultResultsList[I].first; - Constant *Result = DefaultResultsList[I].second; + for (const auto &I : DefaultResultsList) { + PHINode *PHI = I.first; + Constant *Result = I.second; DefaultResults[PHI] = Result; } @@ -3974,6 +4188,8 @@ 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); @@ -3984,7 +4200,7 @@ 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. @@ -4001,9 +4217,12 @@ static bool SwitchToLookupTable(SwitchInst *SI, CommonDest->getParent(), CommonDest); + // Make the mask's bitwidth at least 8bit and a power-of-2 to avoid + // unnecessary illegal types. + uint64_t TableSizePowOf2 = NextPowerOf2(std::max(7ULL, TableSize - 1ULL)); + APInt MaskInt(TableSizePowOf2, 0); + APInt One(TableSizePowOf2, 1); // Build bitmask; fill in a 1 bit for every case. - APInt MaskInt(TableSize, 0); - APInt One(TableSize, 1); const ResultListTy &ResultList = ResultLists[PHIs[0]]; for (size_t I = 0, E = ResultList.size(); I != E; ++I) { uint64_t Idx = (ResultList[I].first->getValue() - @@ -4032,11 +4251,11 @@ 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); @@ -4049,6 +4268,16 @@ 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); } @@ -4125,7 +4354,7 @@ bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { SmallPtrSet Succs; for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) { BasicBlock *Dest = IBI->getDestination(i); - if (!Dest->hasAddressTaken() || !Succs.insert(Dest)) { + if (!Dest->hasAddressTaken() || !Succs.insert(Dest).second) { Dest->removePredecessor(BB); IBI->removeDestination(i); --i; --e;