//===- InstructionSimplify.cpp - Fold instruction operands ----------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements routines for folding instructions into simpler forms // that do not require creating new instructions. This does constant folding // ("add i32 1, 1" -> "2") but can also handle non-constant operands, either // returning a constant ("and i32 %x, 0" -> "0") or an already existing value // ("and i32 %x, %x" -> "%x"). All operands are assumed to have already been // simplified: This is usually true and assuming it simplifies the logic (if // they have not been simplified then results are correct but maybe suboptimal). // //===----------------------------------------------------------------------===// #include "llvm/Analysis/InstructionSimplify.h" #include "llvm/ADT/SetVector.h" #include "llvm/ADT/Statistic.h" #include "llvm/Analysis/AliasAnalysis.h" #include "llvm/Analysis/ConstantFolding.h" #include "llvm/Analysis/MemoryBuiltins.h" #include "llvm/Analysis/ValueTracking.h" #include "llvm/IR/ConstantRange.h" #include "llvm/IR/DataLayout.h" #include "llvm/IR/Dominators.h" #include "llvm/IR/GetElementPtrTypeIterator.h" #include "llvm/IR/GlobalAlias.h" #include "llvm/IR/Operator.h" #include "llvm/IR/PatternMatch.h" #include "llvm/IR/ValueHandle.h" #include using namespace llvm; using namespace llvm::PatternMatch; #define DEBUG_TYPE "instsimplify" enum { RecursionLimit = 3 }; STATISTIC(NumExpand, "Number of expansions"); STATISTIC(NumReassoc, "Number of reassociations"); namespace { struct Query { const DataLayout *DL; const TargetLibraryInfo *TLI; const DominatorTree *DT; AssumptionCache *AC; const Instruction *CxtI; Query(const DataLayout *DL, const TargetLibraryInfo *tli, const DominatorTree *dt, AssumptionCache *ac = nullptr, const Instruction *cxti = nullptr) : DL(DL), TLI(tli), DT(dt), AC(ac), CxtI(cxti) {} }; } // end anonymous namespace static Value *SimplifyAndInst(Value *, Value *, const Query &, unsigned); static Value *SimplifyBinOp(unsigned, Value *, Value *, const Query &, unsigned); static Value *SimplifyCmpInst(unsigned, Value *, Value *, const Query &, unsigned); static Value *SimplifyOrInst(Value *, Value *, const Query &, unsigned); static Value *SimplifyXorInst(Value *, Value *, const Query &, unsigned); static Value *SimplifyTruncInst(Value *, Type *, const Query &, unsigned); /// getFalse - For a boolean type, or a vector of boolean type, return false, or /// a vector with every element false, as appropriate for the type. static Constant *getFalse(Type *Ty) { assert(Ty->getScalarType()->isIntegerTy(1) && "Expected i1 type or a vector of i1!"); return Constant::getNullValue(Ty); } /// getTrue - For a boolean type, or a vector of boolean type, return true, or /// a vector with every element true, as appropriate for the type. static Constant *getTrue(Type *Ty) { assert(Ty->getScalarType()->isIntegerTy(1) && "Expected i1 type or a vector of i1!"); return Constant::getAllOnesValue(Ty); } /// isSameCompare - Is V equivalent to the comparison "LHS Pred RHS"? static bool isSameCompare(Value *V, CmpInst::Predicate Pred, Value *LHS, Value *RHS) { CmpInst *Cmp = dyn_cast(V); if (!Cmp) return false; CmpInst::Predicate CPred = Cmp->getPredicate(); Value *CLHS = Cmp->getOperand(0), *CRHS = Cmp->getOperand(1); if (CPred == Pred && CLHS == LHS && CRHS == RHS) return true; return CPred == CmpInst::getSwappedPredicate(Pred) && CLHS == RHS && CRHS == LHS; } /// ValueDominatesPHI - Does the given value dominate the specified phi node? static bool ValueDominatesPHI(Value *V, PHINode *P, const DominatorTree *DT) { Instruction *I = dyn_cast(V); if (!I) // Arguments and constants dominate all instructions. return true; // If we are processing instructions (and/or basic blocks) that have not been // fully added to a function, the parent nodes may still be null. Simply // return the conservative answer in these cases. if (!I->getParent() || !P->getParent() || !I->getParent()->getParent()) return false; // If we have a DominatorTree then do a precise test. if (DT) { if (!DT->isReachableFromEntry(P->getParent())) return true; if (!DT->isReachableFromEntry(I->getParent())) return false; return DT->dominates(I, P); } // Otherwise, if the instruction is in the entry block, and is not an invoke, // then it obviously dominates all phi nodes. if (I->getParent() == &I->getParent()->getParent()->getEntryBlock() && !isa(I)) return true; return false; } /// ExpandBinOp - Simplify "A op (B op' C)" by distributing op over op', turning /// it into "(A op B) op' (A op C)". Here "op" is given by Opcode and "op'" is /// given by OpcodeToExpand, while "A" corresponds to LHS and "B op' C" to RHS. /// Also performs the transform "(A op' B) op C" -> "(A op C) op' (B op C)". /// Returns the simplified value, or null if no simplification was performed. static Value *ExpandBinOp(unsigned Opcode, Value *LHS, Value *RHS, unsigned OpcToExpand, const Query &Q, unsigned MaxRecurse) { Instruction::BinaryOps OpcodeToExpand = (Instruction::BinaryOps)OpcToExpand; // Recursion is always used, so bail out at once if we already hit the limit. if (!MaxRecurse--) return nullptr; // Check whether the expression has the form "(A op' B) op C". if (BinaryOperator *Op0 = dyn_cast(LHS)) if (Op0->getOpcode() == OpcodeToExpand) { // It does! Try turning it into "(A op C) op' (B op C)". Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; // Do "A op C" and "B op C" both simplify? if (Value *L = SimplifyBinOp(Opcode, A, C, Q, MaxRecurse)) if (Value *R = SimplifyBinOp(Opcode, B, C, Q, MaxRecurse)) { // They do! Return "L op' R" if it simplifies or is already available. // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. if ((L == A && R == B) || (Instruction::isCommutative(OpcodeToExpand) && L == B && R == A)) { ++NumExpand; return LHS; } // Otherwise return "L op' R" if it simplifies. if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, Q, MaxRecurse)) { ++NumExpand; return V; } } } // Check whether the expression has the form "A op (B op' C)". if (BinaryOperator *Op1 = dyn_cast(RHS)) if (Op1->getOpcode() == OpcodeToExpand) { // It does! Try turning it into "(A op B) op' (A op C)". Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); // Do "A op B" and "A op C" both simplify? if (Value *L = SimplifyBinOp(Opcode, A, B, Q, MaxRecurse)) if (Value *R = SimplifyBinOp(Opcode, A, C, Q, MaxRecurse)) { // They do! Return "L op' R" if it simplifies or is already available. // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. if ((L == B && R == C) || (Instruction::isCommutative(OpcodeToExpand) && L == C && R == B)) { ++NumExpand; return RHS; } // Otherwise return "L op' R" if it simplifies. if (Value *V = SimplifyBinOp(OpcodeToExpand, L, R, Q, MaxRecurse)) { ++NumExpand; return V; } } } return nullptr; } /// SimplifyAssociativeBinOp - Generic simplifications for associative binary /// operations. Returns the simpler value, or null if none was found. static Value *SimplifyAssociativeBinOp(unsigned Opc, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { Instruction::BinaryOps Opcode = (Instruction::BinaryOps)Opc; assert(Instruction::isAssociative(Opcode) && "Not an associative operation!"); // Recursion is always used, so bail out at once if we already hit the limit. if (!MaxRecurse--) return nullptr; BinaryOperator *Op0 = dyn_cast(LHS); BinaryOperator *Op1 = dyn_cast(RHS); // Transform: "(A op B) op C" ==> "A op (B op C)" if it simplifies completely. if (Op0 && Op0->getOpcode() == Opcode) { Value *A = Op0->getOperand(0); Value *B = Op0->getOperand(1); Value *C = RHS; // Does "B op C" simplify? if (Value *V = SimplifyBinOp(Opcode, B, C, Q, MaxRecurse)) { // It does! Return "A op V" if it simplifies or is already available. // If V equals B then "A op V" is just the LHS. if (V == B) return LHS; // Otherwise return "A op V" if it simplifies. if (Value *W = SimplifyBinOp(Opcode, A, V, Q, MaxRecurse)) { ++NumReassoc; return W; } } } // Transform: "A op (B op C)" ==> "(A op B) op C" if it simplifies completely. if (Op1 && Op1->getOpcode() == Opcode) { Value *A = LHS; Value *B = Op1->getOperand(0); Value *C = Op1->getOperand(1); // Does "A op B" simplify? if (Value *V = SimplifyBinOp(Opcode, A, B, Q, MaxRecurse)) { // It does! Return "V op C" if it simplifies or is already available. // If V equals B then "V op C" is just the RHS. if (V == B) return RHS; // Otherwise return "V op C" if it simplifies. if (Value *W = SimplifyBinOp(Opcode, V, C, Q, MaxRecurse)) { ++NumReassoc; return W; } } } // The remaining transforms require commutativity as well as associativity. if (!Instruction::isCommutative(Opcode)) return nullptr; // Transform: "(A op B) op C" ==> "(C op A) op B" if it simplifies completely. if (Op0 && Op0->getOpcode() == Opcode) { Value *A = Op0->getOperand(0); Value *B = Op0->getOperand(1); Value *C = RHS; // Does "C op A" simplify? if (Value *V = SimplifyBinOp(Opcode, C, A, Q, MaxRecurse)) { // It does! Return "V op B" if it simplifies or is already available. // If V equals A then "V op B" is just the LHS. if (V == A) return LHS; // Otherwise return "V op B" if it simplifies. if (Value *W = SimplifyBinOp(Opcode, V, B, Q, MaxRecurse)) { ++NumReassoc; return W; } } } // Transform: "A op (B op C)" ==> "B op (C op A)" if it simplifies completely. if (Op1 && Op1->getOpcode() == Opcode) { Value *A = LHS; Value *B = Op1->getOperand(0); Value *C = Op1->getOperand(1); // Does "C op A" simplify? if (Value *V = SimplifyBinOp(Opcode, C, A, Q, MaxRecurse)) { // It does! Return "B op V" if it simplifies or is already available. // If V equals C then "B op V" is just the RHS. if (V == C) return RHS; // Otherwise return "B op V" if it simplifies. if (Value *W = SimplifyBinOp(Opcode, B, V, Q, MaxRecurse)) { ++NumReassoc; return W; } } } return nullptr; } /// ThreadBinOpOverSelect - In the case of a binary operation with a select /// instruction as an operand, try to simplify the binop by seeing whether /// evaluating it on both branches of the select results in the same value. /// Returns the common value if so, otherwise returns null. static Value *ThreadBinOpOverSelect(unsigned Opcode, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { // Recursion is always used, so bail out at once if we already hit the limit. if (!MaxRecurse--) return nullptr; SelectInst *SI; if (isa(LHS)) { SI = cast(LHS); } else { assert(isa(RHS) && "No select instruction operand!"); SI = cast(RHS); } // Evaluate the BinOp on the true and false branches of the select. Value *TV; Value *FV; if (SI == LHS) { TV = SimplifyBinOp(Opcode, SI->getTrueValue(), RHS, Q, MaxRecurse); FV = SimplifyBinOp(Opcode, SI->getFalseValue(), RHS, Q, MaxRecurse); } else { TV = SimplifyBinOp(Opcode, LHS, SI->getTrueValue(), Q, MaxRecurse); FV = SimplifyBinOp(Opcode, LHS, SI->getFalseValue(), Q, MaxRecurse); } // If they simplified to the same value, then return the common value. // If they both failed to simplify then return null. if (TV == FV) return TV; // If one branch simplified to undef, return the other one. if (TV && isa(TV)) return FV; if (FV && isa(FV)) return TV; // If applying the operation did not change the true and false select values, // then the result of the binop is the select itself. if (TV == SI->getTrueValue() && FV == SI->getFalseValue()) return SI; // If one branch simplified and the other did not, and the simplified // value is equal to the unsimplified one, return the simplified value. // For example, select (cond, X, X & Z) & Z -> X & Z. if ((FV && !TV) || (TV && !FV)) { // Check that the simplified value has the form "X op Y" where "op" is the // same as the original operation. Instruction *Simplified = dyn_cast(FV ? FV : TV); if (Simplified && Simplified->getOpcode() == Opcode) { // The value that didn't simplify is "UnsimplifiedLHS op UnsimplifiedRHS". // We already know that "op" is the same as for the simplified value. See // if the operands match too. If so, return the simplified value. Value *UnsimplifiedBranch = FV ? SI->getTrueValue() : SI->getFalseValue(); Value *UnsimplifiedLHS = SI == LHS ? UnsimplifiedBranch : LHS; Value *UnsimplifiedRHS = SI == LHS ? RHS : UnsimplifiedBranch; if (Simplified->getOperand(0) == UnsimplifiedLHS && Simplified->getOperand(1) == UnsimplifiedRHS) return Simplified; if (Simplified->isCommutative() && Simplified->getOperand(1) == UnsimplifiedLHS && Simplified->getOperand(0) == UnsimplifiedRHS) return Simplified; } } return nullptr; } /// ThreadCmpOverSelect - In the case of a comparison with a select instruction, /// try to simplify the comparison by seeing whether both branches of the select /// result in the same value. Returns the common value if so, otherwise returns /// null. static Value *ThreadCmpOverSelect(CmpInst::Predicate Pred, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { // Recursion is always used, so bail out at once if we already hit the limit. if (!MaxRecurse--) return nullptr; // Make sure the select is on the LHS. if (!isa(LHS)) { std::swap(LHS, RHS); Pred = CmpInst::getSwappedPredicate(Pred); } assert(isa(LHS) && "Not comparing with a select instruction!"); SelectInst *SI = cast(LHS); Value *Cond = SI->getCondition(); Value *TV = SI->getTrueValue(); Value *FV = SI->getFalseValue(); // Now that we have "cmp select(Cond, TV, FV), RHS", analyse it. // Does "cmp TV, RHS" simplify? Value *TCmp = SimplifyCmpInst(Pred, TV, RHS, Q, MaxRecurse); if (TCmp == Cond) { // It not only simplified, it simplified to the select condition. Replace // it with 'true'. TCmp = getTrue(Cond->getType()); } else if (!TCmp) { // It didn't simplify. However if "cmp TV, RHS" is equal to the select // condition then we can replace it with 'true'. Otherwise give up. if (!isSameCompare(Cond, Pred, TV, RHS)) return nullptr; TCmp = getTrue(Cond->getType()); } // Does "cmp FV, RHS" simplify? Value *FCmp = SimplifyCmpInst(Pred, FV, RHS, Q, MaxRecurse); if (FCmp == Cond) { // It not only simplified, it simplified to the select condition. Replace // it with 'false'. FCmp = getFalse(Cond->getType()); } else if (!FCmp) { // It didn't simplify. However if "cmp FV, RHS" is equal to the select // condition then we can replace it with 'false'. Otherwise give up. if (!isSameCompare(Cond, Pred, FV, RHS)) return nullptr; FCmp = getFalse(Cond->getType()); } // If both sides simplified to the same value, then use it as the result of // the original comparison. if (TCmp == FCmp) return TCmp; // The remaining cases only make sense if the select condition has the same // type as the result of the comparison, so bail out if this is not so. if (Cond->getType()->isVectorTy() != RHS->getType()->isVectorTy()) return nullptr; // If the false value simplified to false, then the result of the compare // is equal to "Cond && TCmp". This also catches the case when the false // value simplified to false and the true value to true, returning "Cond". if (match(FCmp, m_Zero())) if (Value *V = SimplifyAndInst(Cond, TCmp, Q, MaxRecurse)) return V; // If the true value simplified to true, then the result of the compare // is equal to "Cond || FCmp". if (match(TCmp, m_One())) if (Value *V = SimplifyOrInst(Cond, FCmp, Q, MaxRecurse)) return V; // Finally, if the false value simplified to true and the true value to // false, then the result of the compare is equal to "!Cond". if (match(FCmp, m_One()) && match(TCmp, m_Zero())) if (Value *V = SimplifyXorInst(Cond, Constant::getAllOnesValue(Cond->getType()), Q, MaxRecurse)) return V; return nullptr; } /// ThreadBinOpOverPHI - In the case of a binary operation with an operand that /// is a PHI instruction, try to simplify the binop by seeing whether evaluating /// it on the incoming phi values yields the same result for every value. If so /// returns the common value, otherwise returns null. static Value *ThreadBinOpOverPHI(unsigned Opcode, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { // Recursion is always used, so bail out at once if we already hit the limit. if (!MaxRecurse--) return nullptr; PHINode *PI; if (isa(LHS)) { PI = cast(LHS); // Bail out if RHS and the phi may be mutually interdependent due to a loop. if (!ValueDominatesPHI(RHS, PI, Q.DT)) return nullptr; } else { assert(isa(RHS) && "No PHI instruction operand!"); PI = cast(RHS); // Bail out if LHS and the phi may be mutually interdependent due to a loop. if (!ValueDominatesPHI(LHS, PI, Q.DT)) return nullptr; } // Evaluate the BinOp on the incoming phi values. Value *CommonValue = nullptr; for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { Value *Incoming = PI->getIncomingValue(i); // If the incoming value is the phi node itself, it can safely be skipped. if (Incoming == PI) continue; Value *V = PI == LHS ? SimplifyBinOp(Opcode, Incoming, RHS, Q, MaxRecurse) : SimplifyBinOp(Opcode, LHS, Incoming, Q, MaxRecurse); // If the operation failed to simplify, or simplified to a different value // to previously, then give up. if (!V || (CommonValue && V != CommonValue)) return nullptr; CommonValue = V; } return CommonValue; } /// ThreadCmpOverPHI - In the case of a comparison with a PHI instruction, try /// try to simplify the comparison by seeing whether comparing with all of the /// incoming phi values yields the same result every time. If so returns the /// common result, otherwise returns null. static Value *ThreadCmpOverPHI(CmpInst::Predicate Pred, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { // Recursion is always used, so bail out at once if we already hit the limit. if (!MaxRecurse--) return nullptr; // Make sure the phi is on the LHS. if (!isa(LHS)) { std::swap(LHS, RHS); Pred = CmpInst::getSwappedPredicate(Pred); } assert(isa(LHS) && "Not comparing with a phi instruction!"); PHINode *PI = cast(LHS); // Bail out if RHS and the phi may be mutually interdependent due to a loop. if (!ValueDominatesPHI(RHS, PI, Q.DT)) return nullptr; // Evaluate the BinOp on the incoming phi values. Value *CommonValue = nullptr; for (unsigned i = 0, e = PI->getNumIncomingValues(); i != e; ++i) { Value *Incoming = PI->getIncomingValue(i); // If the incoming value is the phi node itself, it can safely be skipped. if (Incoming == PI) continue; Value *V = SimplifyCmpInst(Pred, Incoming, RHS, Q, MaxRecurse); // If the operation failed to simplify, or simplified to a different value // to previously, then give up. if (!V || (CommonValue && V != CommonValue)) return nullptr; CommonValue = V; } return CommonValue; } /// SimplifyAddInst - Given operands for an Add, see if we can /// fold the result. If not, this returns null. static Value *SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::Add, CLHS->getType(), Ops, Q.DL, Q.TLI); } // Canonicalize the constant to the RHS. std::swap(Op0, Op1); } // X + undef -> undef if (match(Op1, m_Undef())) return Op1; // X + 0 -> X if (match(Op1, m_Zero())) return Op0; // X + (Y - X) -> Y // (Y - X) + X -> Y // Eg: X + -X -> 0 Value *Y = nullptr; if (match(Op1, m_Sub(m_Value(Y), m_Specific(Op0))) || match(Op0, m_Sub(m_Value(Y), m_Specific(Op1)))) return Y; // X + ~X -> -1 since ~X = -X-1 if (match(Op0, m_Not(m_Specific(Op1))) || match(Op1, m_Not(m_Specific(Op0)))) return Constant::getAllOnesValue(Op0->getType()); /// i1 add -> xor. if (MaxRecurse && Op0->getType()->isIntegerTy(1)) if (Value *V = SimplifyXorInst(Op0, Op1, Q, MaxRecurse-1)) return V; // Try some generic simplifications for associative operations. if (Value *V = SimplifyAssociativeBinOp(Instruction::Add, Op0, Op1, Q, MaxRecurse)) return V; // Threading Add over selects and phi nodes is pointless, so don't bother. // Threading over the select in "A + select(cond, B, C)" means evaluating // "A+B" and "A+C" and seeing if they are equal; but they are equal if and // only if B and C are equal. If B and C are equal then (since we assume // that operands have already been simplified) "select(cond, B, C)" should // have been simplified to the common value of B and C already. Analysing // "A+B" and "A+C" thus gains nothing, but costs compile time. Similarly // for threading over phi nodes. return nullptr; } Value *llvm::SimplifyAddInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyAddInst(Op0, Op1, isNSW, isNUW, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// \brief Compute the base pointer and cumulative constant offsets for V. /// /// This strips all constant offsets off of V, leaving it the base pointer, and /// accumulates the total constant offset applied in the returned constant. It /// returns 0 if V is not a pointer, and returns the constant '0' if there are /// no constant offsets applied. /// /// This is very similar to GetPointerBaseWithConstantOffset except it doesn't /// follow non-inbounds geps. This allows it to remain usable for icmp ult/etc. /// folding. static Constant *stripAndComputeConstantOffsets(const DataLayout *DL, Value *&V, bool AllowNonInbounds = false) { assert(V->getType()->getScalarType()->isPointerTy()); // Without DataLayout, just be conservative for now. Theoretically, more could // be done in this case. if (!DL) return ConstantInt::get(IntegerType::get(V->getContext(), 64), 0); Type *IntPtrTy = DL->getIntPtrType(V->getType())->getScalarType(); APInt Offset = APInt::getNullValue(IntPtrTy->getIntegerBitWidth()); // Even though we don't look through PHI nodes, we could be called on an // instruction in an unreachable block, which may be on a cycle. SmallPtrSet Visited; Visited.insert(V); do { if (GEPOperator *GEP = dyn_cast(V)) { if ((!AllowNonInbounds && !GEP->isInBounds()) || !GEP->accumulateConstantOffset(*DL, Offset)) break; V = GEP->getPointerOperand(); } else if (Operator::getOpcode(V) == Instruction::BitCast) { V = cast(V)->getOperand(0); } else if (GlobalAlias *GA = dyn_cast(V)) { if (GA->mayBeOverridden()) break; V = GA->getAliasee(); } else { break; } assert(V->getType()->getScalarType()->isPointerTy() && "Unexpected operand type!"); } while (Visited.insert(V).second); Constant *OffsetIntPtr = ConstantInt::get(IntPtrTy, Offset); if (V->getType()->isVectorTy()) return ConstantVector::getSplat(V->getType()->getVectorNumElements(), OffsetIntPtr); return OffsetIntPtr; } /// \brief Compute the constant difference between two pointer values. /// If the difference is not a constant, returns zero. static Constant *computePointerDifference(const DataLayout *DL, Value *LHS, Value *RHS) { Constant *LHSOffset = stripAndComputeConstantOffsets(DL, LHS); Constant *RHSOffset = stripAndComputeConstantOffsets(DL, RHS); // If LHS and RHS are not related via constant offsets to the same base // value, there is nothing we can do here. if (LHS != RHS) return nullptr; // Otherwise, the difference of LHS - RHS can be computed as: // LHS - RHS // = (LHSOffset + Base) - (RHSOffset + Base) // = LHSOffset - RHSOffset return ConstantExpr::getSub(LHSOffset, RHSOffset); } /// SimplifySubInst - Given operands for a Sub, see if we can /// fold the result. If not, this returns null. static Value *SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::Sub, CLHS->getType(), Ops, Q.DL, Q.TLI); } // X - undef -> undef // undef - X -> undef if (match(Op0, m_Undef()) || match(Op1, m_Undef())) return UndefValue::get(Op0->getType()); // X - 0 -> X if (match(Op1, m_Zero())) return Op0; // X - X -> 0 if (Op0 == Op1) return Constant::getNullValue(Op0->getType()); // 0 - X -> 0 if the sub is NUW. if (isNUW && match(Op0, m_Zero())) return Op0; // (X + Y) - Z -> X + (Y - Z) or Y + (X - Z) if everything simplifies. // For example, (X + Y) - Y -> X; (Y + X) - Y -> X Value *X = nullptr, *Y = nullptr, *Z = Op1; if (MaxRecurse && match(Op0, m_Add(m_Value(X), m_Value(Y)))) { // (X + Y) - Z // See if "V === Y - Z" simplifies. if (Value *V = SimplifyBinOp(Instruction::Sub, Y, Z, Q, MaxRecurse-1)) // It does! Now see if "X + V" simplifies. if (Value *W = SimplifyBinOp(Instruction::Add, X, V, Q, MaxRecurse-1)) { // It does, we successfully reassociated! ++NumReassoc; return W; } // See if "V === X - Z" simplifies. if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, Q, MaxRecurse-1)) // It does! Now see if "Y + V" simplifies. if (Value *W = SimplifyBinOp(Instruction::Add, Y, V, Q, MaxRecurse-1)) { // It does, we successfully reassociated! ++NumReassoc; return W; } } // X - (Y + Z) -> (X - Y) - Z or (X - Z) - Y if everything simplifies. // For example, X - (X + 1) -> -1 X = Op0; if (MaxRecurse && match(Op1, m_Add(m_Value(Y), m_Value(Z)))) { // X - (Y + Z) // See if "V === X - Y" simplifies. if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, Q, MaxRecurse-1)) // It does! Now see if "V - Z" simplifies. if (Value *W = SimplifyBinOp(Instruction::Sub, V, Z, Q, MaxRecurse-1)) { // It does, we successfully reassociated! ++NumReassoc; return W; } // See if "V === X - Z" simplifies. if (Value *V = SimplifyBinOp(Instruction::Sub, X, Z, Q, MaxRecurse-1)) // It does! Now see if "V - Y" simplifies. if (Value *W = SimplifyBinOp(Instruction::Sub, V, Y, Q, MaxRecurse-1)) { // It does, we successfully reassociated! ++NumReassoc; return W; } } // Z - (X - Y) -> (Z - X) + Y if everything simplifies. // For example, X - (X - Y) -> Y. Z = Op0; if (MaxRecurse && match(Op1, m_Sub(m_Value(X), m_Value(Y)))) // Z - (X - Y) // See if "V === Z - X" simplifies. if (Value *V = SimplifyBinOp(Instruction::Sub, Z, X, Q, MaxRecurse-1)) // It does! Now see if "V + Y" simplifies. if (Value *W = SimplifyBinOp(Instruction::Add, V, Y, Q, MaxRecurse-1)) { // It does, we successfully reassociated! ++NumReassoc; return W; } // trunc(X) - trunc(Y) -> trunc(X - Y) if everything simplifies. if (MaxRecurse && match(Op0, m_Trunc(m_Value(X))) && match(Op1, m_Trunc(m_Value(Y)))) if (X->getType() == Y->getType()) // See if "V === X - Y" simplifies. if (Value *V = SimplifyBinOp(Instruction::Sub, X, Y, Q, MaxRecurse-1)) // It does! Now see if "trunc V" simplifies. if (Value *W = SimplifyTruncInst(V, Op0->getType(), Q, MaxRecurse-1)) // It does, return the simplified "trunc V". return W; // Variations on GEP(base, I, ...) - GEP(base, i, ...) -> GEP(null, I-i, ...). if (match(Op0, m_PtrToInt(m_Value(X))) && match(Op1, m_PtrToInt(m_Value(Y)))) if (Constant *Result = computePointerDifference(Q.DL, X, Y)) return ConstantExpr::getIntegerCast(Result, Op0->getType(), true); // i1 sub -> xor. if (MaxRecurse && Op0->getType()->isIntegerTy(1)) if (Value *V = SimplifyXorInst(Op0, Op1, Q, MaxRecurse-1)) return V; // Threading Sub over selects and phi nodes is pointless, so don't bother. // Threading over the select in "A - select(cond, B, C)" means evaluating // "A-B" and "A-C" and seeing if they are equal; but they are equal if and // only if B and C are equal. If B and C are equal then (since we assume // that operands have already been simplified) "select(cond, B, C)" should // have been simplified to the common value of B and C already. Analysing // "A-B" and "A-C" thus gains nothing, but costs compile time. Similarly // for threading over phi nodes. return nullptr; } Value *llvm::SimplifySubInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifySubInst(Op0, Op1, isNSW, isNUW, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// Given operands for an FAdd, see if we can fold the result. If not, this /// returns null. static Value *SimplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags FMF, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::FAdd, CLHS->getType(), Ops, Q.DL, Q.TLI); } // Canonicalize the constant to the RHS. std::swap(Op0, Op1); } // fadd X, -0 ==> X if (match(Op1, m_NegZero())) return Op0; // fadd X, 0 ==> X, when we know X is not -0 if (match(Op1, m_Zero()) && (FMF.noSignedZeros() || CannotBeNegativeZero(Op0))) return Op0; // fadd [nnan ninf] X, (fsub [nnan ninf] 0, X) ==> 0 // where nnan and ninf have to occur at least once somewhere in this // expression Value *SubOp = nullptr; if (match(Op1, m_FSub(m_AnyZero(), m_Specific(Op0)))) SubOp = Op1; else if (match(Op0, m_FSub(m_AnyZero(), m_Specific(Op1)))) SubOp = Op0; if (SubOp) { Instruction *FSub = cast(SubOp); if ((FMF.noNaNs() || FSub->hasNoNaNs()) && (FMF.noInfs() || FSub->hasNoInfs())) return Constant::getNullValue(Op0->getType()); } return nullptr; } /// Given operands for an FSub, see if we can fold the result. If not, this /// returns null. static Value *SimplifyFSubInst(Value *Op0, Value *Op1, FastMathFlags FMF, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::FSub, CLHS->getType(), Ops, Q.DL, Q.TLI); } } // fsub X, 0 ==> X if (match(Op1, m_Zero())) return Op0; // fsub X, -0 ==> X, when we know X is not -0 if (match(Op1, m_NegZero()) && (FMF.noSignedZeros() || CannotBeNegativeZero(Op0))) return Op0; // fsub 0, (fsub -0.0, X) ==> X Value *X; if (match(Op0, m_AnyZero())) { if (match(Op1, m_FSub(m_NegZero(), m_Value(X)))) return X; if (FMF.noSignedZeros() && match(Op1, m_FSub(m_AnyZero(), m_Value(X)))) return X; } // fsub nnan ninf x, x ==> 0.0 if (FMF.noNaNs() && FMF.noInfs() && Op0 == Op1) return Constant::getNullValue(Op0->getType()); return nullptr; } /// Given the operands for an FMul, see if we can fold the result static Value *SimplifyFMulInst(Value *Op0, Value *Op1, FastMathFlags FMF, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::FMul, CLHS->getType(), Ops, Q.DL, Q.TLI); } // Canonicalize the constant to the RHS. std::swap(Op0, Op1); } // fmul X, 1.0 ==> X if (match(Op1, m_FPOne())) return Op0; // fmul nnan nsz X, 0 ==> 0 if (FMF.noNaNs() && FMF.noSignedZeros() && match(Op1, m_AnyZero())) return Op1; return nullptr; } /// SimplifyMulInst - Given operands for a Mul, see if we can /// fold the result. If not, this returns null. static Value *SimplifyMulInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::Mul, CLHS->getType(), Ops, Q.DL, Q.TLI); } // Canonicalize the constant to the RHS. std::swap(Op0, Op1); } // X * undef -> 0 if (match(Op1, m_Undef())) return Constant::getNullValue(Op0->getType()); // X * 0 -> 0 if (match(Op1, m_Zero())) return Op1; // X * 1 -> X if (match(Op1, m_One())) return Op0; // (X / Y) * Y -> X if the division is exact. Value *X = nullptr; if (match(Op0, m_Exact(m_IDiv(m_Value(X), m_Specific(Op1)))) || // (X / Y) * Y match(Op1, m_Exact(m_IDiv(m_Value(X), m_Specific(Op0))))) // Y * (X / Y) return X; // i1 mul -> and. if (MaxRecurse && Op0->getType()->isIntegerTy(1)) if (Value *V = SimplifyAndInst(Op0, Op1, Q, MaxRecurse-1)) return V; // Try some generic simplifications for associative operations. if (Value *V = SimplifyAssociativeBinOp(Instruction::Mul, Op0, Op1, Q, MaxRecurse)) return V; // Mul distributes over Add. Try some generic simplifications based on this. if (Value *V = ExpandBinOp(Instruction::Mul, Op0, Op1, Instruction::Add, Q, MaxRecurse)) return V; // If the operation is with the result of a select instruction, check whether // operating on either branch of the select always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverSelect(Instruction::Mul, Op0, Op1, Q, MaxRecurse)) return V; // If the operation is with the result of a phi instruction, check whether // operating on all incoming values of the phi always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverPHI(Instruction::Mul, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags FMF, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyFAddInst(Op0, Op1, FMF, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } Value *llvm::SimplifyFSubInst(Value *Op0, Value *Op1, FastMathFlags FMF, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyFSubInst(Op0, Op1, FMF, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } Value *llvm::SimplifyFMulInst(Value *Op0, Value *Op1, FastMathFlags FMF, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyFMulInst(Op0, Op1, FMF, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } Value *llvm::SimplifyMulInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyMulInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyDiv - Given operands for an SDiv or UDiv, see if we can /// fold the result. If not, this returns null. static Value *SimplifyDiv(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Constant *C0 = dyn_cast(Op0)) { if (Constant *C1 = dyn_cast(Op1)) { Constant *Ops[] = { C0, C1 }; return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, Q.DL, Q.TLI); } } bool isSigned = Opcode == Instruction::SDiv; // X / undef -> undef if (match(Op1, m_Undef())) return Op1; // X / 0 -> undef, we don't need to preserve faults! if (match(Op1, m_Zero())) return UndefValue::get(Op1->getType()); // undef / X -> 0 if (match(Op0, m_Undef())) return Constant::getNullValue(Op0->getType()); // 0 / X -> 0, we don't need to preserve faults! if (match(Op0, m_Zero())) return Op0; // X / 1 -> X if (match(Op1, m_One())) return Op0; if (Op0->getType()->isIntegerTy(1)) // It can't be division by zero, hence it must be division by one. return Op0; // X / X -> 1 if (Op0 == Op1) return ConstantInt::get(Op0->getType(), 1); // (X * Y) / Y -> X if the multiplication does not overflow. Value *X = nullptr, *Y = nullptr; if (match(Op0, m_Mul(m_Value(X), m_Value(Y))) && (X == Op1 || Y == Op1)) { if (Y != Op1) std::swap(X, Y); // Ensure expression is (X * Y) / Y, Y = Op1 OverflowingBinaryOperator *Mul = cast(Op0); // If the Mul knows it does not overflow, then we are good to go. if ((isSigned && Mul->hasNoSignedWrap()) || (!isSigned && Mul->hasNoUnsignedWrap())) return X; // If X has the form X = A / Y then X * Y cannot overflow. if (BinaryOperator *Div = dyn_cast(X)) if (Div->getOpcode() == Opcode && Div->getOperand(1) == Y) return X; } // (X rem Y) / Y -> 0 if ((isSigned && match(Op0, m_SRem(m_Value(), m_Specific(Op1)))) || (!isSigned && match(Op0, m_URem(m_Value(), m_Specific(Op1))))) return Constant::getNullValue(Op0->getType()); // (X /u C1) /u C2 -> 0 if C1 * C2 overflow ConstantInt *C1, *C2; if (!isSigned && match(Op0, m_UDiv(m_Value(X), m_ConstantInt(C1))) && match(Op1, m_ConstantInt(C2))) { bool Overflow; C1->getValue().umul_ov(C2->getValue(), Overflow); if (Overflow) return Constant::getNullValue(Op0->getType()); } // If the operation is with the result of a select instruction, check whether // operating on either branch of the select always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, Q, MaxRecurse)) return V; // If the operation is with the result of a phi instruction, check whether // operating on all incoming values of the phi always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } /// SimplifySDivInst - Given operands for an SDiv, see if we can /// fold the result. If not, this returns null. static Value *SimplifySDivInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyDiv(Instruction::SDiv, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifySDivInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifySDivInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyUDivInst - Given operands for a UDiv, see if we can /// fold the result. If not, this returns null. static Value *SimplifyUDivInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyDiv(Instruction::UDiv, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifyUDivInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyUDivInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } static Value *SimplifyFDivInst(Value *Op0, Value *Op1, const Query &Q, unsigned) { // undef / X -> undef (the undef could be a snan). if (match(Op0, m_Undef())) return Op0; // X / undef -> undef if (match(Op1, m_Undef())) return Op1; return nullptr; } Value *llvm::SimplifyFDivInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyFDivInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyRem - Given operands for an SRem or URem, see if we can /// fold the result. If not, this returns null. static Value *SimplifyRem(Instruction::BinaryOps Opcode, Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Constant *C0 = dyn_cast(Op0)) { if (Constant *C1 = dyn_cast(Op1)) { Constant *Ops[] = { C0, C1 }; return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, Q.DL, Q.TLI); } } // X % undef -> undef if (match(Op1, m_Undef())) return Op1; // undef % X -> 0 if (match(Op0, m_Undef())) return Constant::getNullValue(Op0->getType()); // 0 % X -> 0, we don't need to preserve faults! if (match(Op0, m_Zero())) return Op0; // X % 0 -> undef, we don't need to preserve faults! if (match(Op1, m_Zero())) return UndefValue::get(Op0->getType()); // X % 1 -> 0 if (match(Op1, m_One())) return Constant::getNullValue(Op0->getType()); if (Op0->getType()->isIntegerTy(1)) // It can't be remainder by zero, hence it must be remainder by one. return Constant::getNullValue(Op0->getType()); // X % X -> 0 if (Op0 == Op1) return Constant::getNullValue(Op0->getType()); // (X % Y) % Y -> X % Y if ((Opcode == Instruction::SRem && match(Op0, m_SRem(m_Value(), m_Specific(Op1)))) || (Opcode == Instruction::URem && match(Op0, m_URem(m_Value(), m_Specific(Op1))))) return Op0; // If the operation is with the result of a select instruction, check whether // operating on either branch of the select always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, Q, MaxRecurse)) return V; // If the operation is with the result of a phi instruction, check whether // operating on all incoming values of the phi always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } /// SimplifySRemInst - Given operands for an SRem, see if we can /// fold the result. If not, this returns null. static Value *SimplifySRemInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyRem(Instruction::SRem, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifySRemInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifySRemInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyURemInst - Given operands for a URem, see if we can /// fold the result. If not, this returns null. static Value *SimplifyURemInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyRem(Instruction::URem, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifyURemInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyURemInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } static Value *SimplifyFRemInst(Value *Op0, Value *Op1, const Query &, unsigned) { // undef % X -> undef (the undef could be a snan). if (match(Op0, m_Undef())) return Op0; // X % undef -> undef if (match(Op1, m_Undef())) return Op1; return nullptr; } Value *llvm::SimplifyFRemInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyFRemInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// isUndefShift - Returns true if a shift by \c Amount always yields undef. static bool isUndefShift(Value *Amount) { Constant *C = dyn_cast(Amount); if (!C) return false; // X shift by undef -> undef because it may shift by the bitwidth. if (isa(C)) return true; // Shifting by the bitwidth or more is undefined. if (ConstantInt *CI = dyn_cast(C)) if (CI->getValue().getLimitedValue() >= CI->getType()->getScalarSizeInBits()) return true; // If all lanes of a vector shift are undefined the whole shift is. if (isa(C) || isa(C)) { for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E; ++I) if (!isUndefShift(C->getAggregateElement(I))) return false; return true; } return false; } /// SimplifyShift - Given operands for an Shl, LShr or AShr, see if we can /// fold the result. If not, this returns null. static Value *SimplifyShift(unsigned Opcode, Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Constant *C0 = dyn_cast(Op0)) { if (Constant *C1 = dyn_cast(Op1)) { Constant *Ops[] = { C0, C1 }; return ConstantFoldInstOperands(Opcode, C0->getType(), Ops, Q.DL, Q.TLI); } } // 0 shift by X -> 0 if (match(Op0, m_Zero())) return Op0; // X shift by 0 -> X if (match(Op1, m_Zero())) return Op0; // Fold undefined shifts. if (isUndefShift(Op1)) return UndefValue::get(Op0->getType()); // If the operation is with the result of a select instruction, check whether // operating on either branch of the select always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverSelect(Opcode, Op0, Op1, Q, MaxRecurse)) return V; // If the operation is with the result of a phi instruction, check whether // operating on all incoming values of the phi always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverPHI(Opcode, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } /// \brief Given operands for an Shl, LShr or AShr, see if we can /// fold the result. If not, this returns null. static Value *SimplifyRightShift(unsigned Opcode, Value *Op0, Value *Op1, bool isExact, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyShift(Opcode, Op0, Op1, Q, MaxRecurse)) return V; // X >> X -> 0 if (Op0 == Op1) return Constant::getNullValue(Op0->getType()); // undef >> X -> 0 // undef >> X -> undef (if it's exact) if (match(Op0, m_Undef())) return isExact ? Op0 : Constant::getNullValue(Op0->getType()); // The low bit cannot be shifted out of an exact shift if it is set. if (isExact) { unsigned BitWidth = Op0->getType()->getScalarSizeInBits(); APInt Op0KnownZero(BitWidth, 0); APInt Op0KnownOne(BitWidth, 0); computeKnownBits(Op0, Op0KnownZero, Op0KnownOne, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT); if (Op0KnownOne[0]) return Op0; } return nullptr; } /// SimplifyShlInst - Given operands for an Shl, see if we can /// fold the result. If not, this returns null. static Value *SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyShift(Instruction::Shl, Op0, Op1, Q, MaxRecurse)) return V; // undef << X -> 0 // undef << X -> undef if (if it's NSW/NUW) if (match(Op0, m_Undef())) return isNSW || isNUW ? Op0 : Constant::getNullValue(Op0->getType()); // (X >> A) << A -> X Value *X; if (match(Op0, m_Exact(m_Shr(m_Value(X), m_Specific(Op1))))) return X; return nullptr; } Value *llvm::SimplifyShlInst(Value *Op0, Value *Op1, bool isNSW, bool isNUW, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyShlInst(Op0, Op1, isNSW, isNUW, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyLShrInst - Given operands for an LShr, see if we can /// fold the result. If not, this returns null. static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyRightShift(Instruction::LShr, Op0, Op1, isExact, Q, MaxRecurse)) return V; // (X << A) >> A -> X Value *X; if (match(Op0, m_NUWShl(m_Value(X), m_Specific(Op1)))) return X; return nullptr; } Value *llvm::SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyLShrInst(Op0, Op1, isExact, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyAShrInst - Given operands for an AShr, see if we can /// fold the result. If not, this returns null. static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, const Query &Q, unsigned MaxRecurse) { if (Value *V = SimplifyRightShift(Instruction::AShr, Op0, Op1, isExact, Q, MaxRecurse)) return V; // all ones >>a X -> all ones if (match(Op0, m_AllOnes())) return Op0; // (X << A) >> A -> X Value *X; if (match(Op0, m_NSWShl(m_Value(X), m_Specific(Op1)))) return X; // Arithmetic shifting an all-sign-bit value is a no-op. unsigned NumSignBits = ComputeNumSignBits(Op0, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (NumSignBits == Op0->getType()->getScalarSizeInBits()) return Op0; return nullptr; } Value *llvm::SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyAShrInst(Op0, Op1, isExact, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } static Value *simplifyUnsignedRangeCheck(ICmpInst *ZeroICmp, ICmpInst *UnsignedICmp, bool IsAnd) { Value *X, *Y; ICmpInst::Predicate EqPred; if (!match(ZeroICmp, m_ICmp(EqPred, m_Value(Y), m_Zero())) || !ICmpInst::isEquality(EqPred)) return nullptr; ICmpInst::Predicate UnsignedPred; if (match(UnsignedICmp, m_ICmp(UnsignedPred, m_Value(X), m_Specific(Y))) && ICmpInst::isUnsigned(UnsignedPred)) ; else if (match(UnsignedICmp, m_ICmp(UnsignedPred, m_Value(Y), m_Specific(X))) && ICmpInst::isUnsigned(UnsignedPred)) UnsignedPred = ICmpInst::getSwappedPredicate(UnsignedPred); else return nullptr; // X < Y && Y != 0 --> X < Y // X < Y || Y != 0 --> Y != 0 if (UnsignedPred == ICmpInst::ICMP_ULT && EqPred == ICmpInst::ICMP_NE) return IsAnd ? UnsignedICmp : ZeroICmp; // X >= Y || Y != 0 --> true // X >= Y || Y == 0 --> X >= Y if (UnsignedPred == ICmpInst::ICMP_UGE && !IsAnd) { if (EqPred == ICmpInst::ICMP_NE) return getTrue(UnsignedICmp->getType()); return UnsignedICmp; } // X < Y && Y == 0 --> false if (UnsignedPred == ICmpInst::ICMP_ULT && EqPred == ICmpInst::ICMP_EQ && IsAnd) return getFalse(UnsignedICmp->getType()); return nullptr; } // Simplify (and (icmp ...) (icmp ...)) to true when we can tell that the range // of possible values cannot be satisfied. static Value *SimplifyAndOfICmps(ICmpInst *Op0, ICmpInst *Op1) { ICmpInst::Predicate Pred0, Pred1; ConstantInt *CI1, *CI2; Value *V; if (Value *X = simplifyUnsignedRangeCheck(Op0, Op1, /*IsAnd=*/true)) return X; if (!match(Op0, m_ICmp(Pred0, m_Add(m_Value(V), m_ConstantInt(CI1)), m_ConstantInt(CI2)))) return nullptr; if (!match(Op1, m_ICmp(Pred1, m_Specific(V), m_Specific(CI1)))) return nullptr; Type *ITy = Op0->getType(); auto *AddInst = cast(Op0->getOperand(0)); bool isNSW = AddInst->hasNoSignedWrap(); bool isNUW = AddInst->hasNoUnsignedWrap(); const APInt &CI1V = CI1->getValue(); const APInt &CI2V = CI2->getValue(); const APInt Delta = CI2V - CI1V; if (CI1V.isStrictlyPositive()) { if (Delta == 2) { if (Pred0 == ICmpInst::ICMP_ULT && Pred1 == ICmpInst::ICMP_SGT) return getFalse(ITy); if (Pred0 == ICmpInst::ICMP_SLT && Pred1 == ICmpInst::ICMP_SGT && isNSW) return getFalse(ITy); } if (Delta == 1) { if (Pred0 == ICmpInst::ICMP_ULE && Pred1 == ICmpInst::ICMP_SGT) return getFalse(ITy); if (Pred0 == ICmpInst::ICMP_SLE && Pred1 == ICmpInst::ICMP_SGT && isNSW) return getFalse(ITy); } } if (CI1V.getBoolValue() && isNUW) { if (Delta == 2) if (Pred0 == ICmpInst::ICMP_ULT && Pred1 == ICmpInst::ICMP_UGT) return getFalse(ITy); if (Delta == 1) if (Pred0 == ICmpInst::ICMP_ULE && Pred1 == ICmpInst::ICMP_UGT) return getFalse(ITy); } return nullptr; } /// SimplifyAndInst - Given operands for an And, see if we can /// fold the result. If not, this returns null. static Value *SimplifyAndInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::And, CLHS->getType(), Ops, Q.DL, Q.TLI); } // Canonicalize the constant to the RHS. std::swap(Op0, Op1); } // X & undef -> 0 if (match(Op1, m_Undef())) return Constant::getNullValue(Op0->getType()); // X & X = X if (Op0 == Op1) return Op0; // X & 0 = 0 if (match(Op1, m_Zero())) return Op1; // X & -1 = X if (match(Op1, m_AllOnes())) return Op0; // A & ~A = ~A & A = 0 if (match(Op0, m_Not(m_Specific(Op1))) || match(Op1, m_Not(m_Specific(Op0)))) return Constant::getNullValue(Op0->getType()); // (A | ?) & A = A Value *A = nullptr, *B = nullptr; if (match(Op0, m_Or(m_Value(A), m_Value(B))) && (A == Op1 || B == Op1)) return Op1; // A & (A | ?) = A if (match(Op1, m_Or(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) return Op0; // A & (-A) = A if A is a power of two or zero. if (match(Op0, m_Neg(m_Specific(Op1))) || match(Op1, m_Neg(m_Specific(Op0)))) { if (isKnownToBeAPowerOfTwo(Op0, /*OrZero*/ true, 0, Q.AC, Q.CxtI, Q.DT)) return Op0; if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, Q.AC, Q.CxtI, Q.DT)) return Op1; } if (auto *ICILHS = dyn_cast(Op0)) { if (auto *ICIRHS = dyn_cast(Op1)) { if (Value *V = SimplifyAndOfICmps(ICILHS, ICIRHS)) return V; if (Value *V = SimplifyAndOfICmps(ICIRHS, ICILHS)) return V; } } // Try some generic simplifications for associative operations. if (Value *V = SimplifyAssociativeBinOp(Instruction::And, Op0, Op1, Q, MaxRecurse)) return V; // And distributes over Or. Try some generic simplifications based on this. if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Or, Q, MaxRecurse)) return V; // And distributes over Xor. Try some generic simplifications based on this. if (Value *V = ExpandBinOp(Instruction::And, Op0, Op1, Instruction::Xor, Q, MaxRecurse)) return V; // If the operation is with the result of a select instruction, check whether // operating on either branch of the select always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverSelect(Instruction::And, Op0, Op1, Q, MaxRecurse)) return V; // If the operation is with the result of a phi instruction, check whether // operating on all incoming values of the phi always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverPHI(Instruction::And, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifyAndInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyAndInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } // Simplify (or (icmp ...) (icmp ...)) to true when we can tell that the union // contains all possible values. static Value *SimplifyOrOfICmps(ICmpInst *Op0, ICmpInst *Op1) { ICmpInst::Predicate Pred0, Pred1; ConstantInt *CI1, *CI2; Value *V; if (Value *X = simplifyUnsignedRangeCheck(Op0, Op1, /*IsAnd=*/false)) return X; if (!match(Op0, m_ICmp(Pred0, m_Add(m_Value(V), m_ConstantInt(CI1)), m_ConstantInt(CI2)))) return nullptr; if (!match(Op1, m_ICmp(Pred1, m_Specific(V), m_Specific(CI1)))) return nullptr; Type *ITy = Op0->getType(); auto *AddInst = cast(Op0->getOperand(0)); bool isNSW = AddInst->hasNoSignedWrap(); bool isNUW = AddInst->hasNoUnsignedWrap(); const APInt &CI1V = CI1->getValue(); const APInt &CI2V = CI2->getValue(); const APInt Delta = CI2V - CI1V; if (CI1V.isStrictlyPositive()) { if (Delta == 2) { if (Pred0 == ICmpInst::ICMP_UGE && Pred1 == ICmpInst::ICMP_SLE) return getTrue(ITy); if (Pred0 == ICmpInst::ICMP_SGE && Pred1 == ICmpInst::ICMP_SLE && isNSW) return getTrue(ITy); } if (Delta == 1) { if (Pred0 == ICmpInst::ICMP_UGT && Pred1 == ICmpInst::ICMP_SLE) return getTrue(ITy); if (Pred0 == ICmpInst::ICMP_SGT && Pred1 == ICmpInst::ICMP_SLE && isNSW) return getTrue(ITy); } } if (CI1V.getBoolValue() && isNUW) { if (Delta == 2) if (Pred0 == ICmpInst::ICMP_UGE && Pred1 == ICmpInst::ICMP_ULE) return getTrue(ITy); if (Delta == 1) if (Pred0 == ICmpInst::ICMP_UGT && Pred1 == ICmpInst::ICMP_ULE) return getTrue(ITy); } return nullptr; } /// SimplifyOrInst - Given operands for an Or, see if we can /// fold the result. If not, this returns null. static Value *SimplifyOrInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::Or, CLHS->getType(), Ops, Q.DL, Q.TLI); } // Canonicalize the constant to the RHS. std::swap(Op0, Op1); } // X | undef -> -1 if (match(Op1, m_Undef())) return Constant::getAllOnesValue(Op0->getType()); // X | X = X if (Op0 == Op1) return Op0; // X | 0 = X if (match(Op1, m_Zero())) return Op0; // X | -1 = -1 if (match(Op1, m_AllOnes())) return Op1; // A | ~A = ~A | A = -1 if (match(Op0, m_Not(m_Specific(Op1))) || match(Op1, m_Not(m_Specific(Op0)))) return Constant::getAllOnesValue(Op0->getType()); // (A & ?) | A = A Value *A = nullptr, *B = nullptr; if (match(Op0, m_And(m_Value(A), m_Value(B))) && (A == Op1 || B == Op1)) return Op1; // A | (A & ?) = A if (match(Op1, m_And(m_Value(A), m_Value(B))) && (A == Op0 || B == Op0)) return Op0; // ~(A & ?) | A = -1 if (match(Op0, m_Not(m_And(m_Value(A), m_Value(B)))) && (A == Op1 || B == Op1)) return Constant::getAllOnesValue(Op1->getType()); // A | ~(A & ?) = -1 if (match(Op1, m_Not(m_And(m_Value(A), m_Value(B)))) && (A == Op0 || B == Op0)) return Constant::getAllOnesValue(Op0->getType()); if (auto *ICILHS = dyn_cast(Op0)) { if (auto *ICIRHS = dyn_cast(Op1)) { if (Value *V = SimplifyOrOfICmps(ICILHS, ICIRHS)) return V; if (Value *V = SimplifyOrOfICmps(ICIRHS, ICILHS)) return V; } } // Try some generic simplifications for associative operations. if (Value *V = SimplifyAssociativeBinOp(Instruction::Or, Op0, Op1, Q, MaxRecurse)) return V; // Or distributes over And. Try some generic simplifications based on this. if (Value *V = ExpandBinOp(Instruction::Or, Op0, Op1, Instruction::And, Q, MaxRecurse)) return V; // If the operation is with the result of a select instruction, check whether // operating on either branch of the select always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverSelect(Instruction::Or, Op0, Op1, Q, MaxRecurse)) return V; // (A & C)|(B & D) Value *C = nullptr, *D = nullptr; if (match(Op0, m_And(m_Value(A), m_Value(C))) && match(Op1, m_And(m_Value(B), m_Value(D)))) { ConstantInt *C1 = dyn_cast(C); ConstantInt *C2 = dyn_cast(D); if (C1 && C2 && (C1->getValue() == ~C2->getValue())) { // (A & C1)|(B & C2) // If we have: ((V + N) & C1) | (V & C2) // .. and C2 = ~C1 and C2 is 0+1+ and (N & C2) == 0 // replace with V+N. Value *V1, *V2; if ((C2->getValue() & (C2->getValue() + 1)) == 0 && // C2 == 0+1+ match(A, m_Add(m_Value(V1), m_Value(V2)))) { // Add commutes, try both ways. if (V1 == B && MaskedValueIsZero(V2, C2->getValue(), Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return A; if (V2 == B && MaskedValueIsZero(V1, C2->getValue(), Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return A; } // Or commutes, try both ways. if ((C1->getValue() & (C1->getValue() + 1)) == 0 && match(B, m_Add(m_Value(V1), m_Value(V2)))) { // Add commutes, try both ways. if (V1 == A && MaskedValueIsZero(V2, C1->getValue(), Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return B; if (V2 == A && MaskedValueIsZero(V1, C1->getValue(), Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return B; } } } // If the operation is with the result of a phi instruction, check whether // operating on all incoming values of the phi always yields the same value. if (isa(Op0) || isa(Op1)) if (Value *V = ThreadBinOpOverPHI(Instruction::Or, Op0, Op1, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifyOrInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyOrInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyXorInst - Given operands for a Xor, see if we can /// fold the result. If not, this returns null. static Value *SimplifyXorInst(Value *Op0, Value *Op1, const Query &Q, unsigned MaxRecurse) { if (Constant *CLHS = dyn_cast(Op0)) { if (Constant *CRHS = dyn_cast(Op1)) { Constant *Ops[] = { CLHS, CRHS }; return ConstantFoldInstOperands(Instruction::Xor, CLHS->getType(), Ops, Q.DL, Q.TLI); } // Canonicalize the constant to the RHS. std::swap(Op0, Op1); } // A ^ undef -> undef if (match(Op1, m_Undef())) return Op1; // A ^ 0 = A if (match(Op1, m_Zero())) return Op0; // A ^ A = 0 if (Op0 == Op1) return Constant::getNullValue(Op0->getType()); // A ^ ~A = ~A ^ A = -1 if (match(Op0, m_Not(m_Specific(Op1))) || match(Op1, m_Not(m_Specific(Op0)))) return Constant::getAllOnesValue(Op0->getType()); // Try some generic simplifications for associative operations. if (Value *V = SimplifyAssociativeBinOp(Instruction::Xor, Op0, Op1, Q, MaxRecurse)) return V; // Threading Xor over selects and phi nodes is pointless, so don't bother. // Threading over the select in "A ^ select(cond, B, C)" means evaluating // "A^B" and "A^C" and seeing if they are equal; but they are equal if and // only if B and C are equal. If B and C are equal then (since we assume // that operands have already been simplified) "select(cond, B, C)" should // have been simplified to the common value of B and C already. Analysing // "A^B" and "A^C" thus gains nothing, but costs compile time. Similarly // for threading over phi nodes. return nullptr; } Value *llvm::SimplifyXorInst(Value *Op0, Value *Op1, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyXorInst(Op0, Op1, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } static Type *GetCompareTy(Value *Op) { return CmpInst::makeCmpResultType(Op->getType()); } /// ExtractEquivalentCondition - Rummage around inside V looking for something /// equivalent to the comparison "LHS Pred RHS". Return such a value if found, /// otherwise return null. Helper function for analyzing max/min idioms. static Value *ExtractEquivalentCondition(Value *V, CmpInst::Predicate Pred, Value *LHS, Value *RHS) { SelectInst *SI = dyn_cast(V); if (!SI) return nullptr; CmpInst *Cmp = dyn_cast(SI->getCondition()); if (!Cmp) return nullptr; Value *CmpLHS = Cmp->getOperand(0), *CmpRHS = Cmp->getOperand(1); if (Pred == Cmp->getPredicate() && LHS == CmpLHS && RHS == CmpRHS) return Cmp; if (Pred == CmpInst::getSwappedPredicate(Cmp->getPredicate()) && LHS == CmpRHS && RHS == CmpLHS) return Cmp; return nullptr; } // A significant optimization not implemented here is assuming that alloca // addresses are not equal to incoming argument values. They don't *alias*, // as we say, but that doesn't mean they aren't equal, so we take a // conservative approach. // // This is inspired in part by C++11 5.10p1: // "Two pointers of the same type compare equal if and only if they are both // null, both point to the same function, or both represent the same // address." // // This is pretty permissive. // // It's also partly due to C11 6.5.9p6: // "Two pointers compare equal if and only if both are null pointers, both are // pointers to the same object (including a pointer to an object and a // subobject at its beginning) or function, both are pointers to one past the // last element of the same array object, or one is a pointer to one past the // end of one array object and the other is a pointer to the start of a // different array object that happens to immediately follow the first array // object in the address space.) // // C11's version is more restrictive, however there's no reason why an argument // couldn't be a one-past-the-end value for a stack object in the caller and be // equal to the beginning of a stack object in the callee. // // If the C and C++ standards are ever made sufficiently restrictive in this // area, it may be possible to update LLVM's semantics accordingly and reinstate // this optimization. static Constant *computePointerICmp(const DataLayout *DL, const TargetLibraryInfo *TLI, CmpInst::Predicate Pred, Value *LHS, Value *RHS) { // First, skip past any trivial no-ops. LHS = LHS->stripPointerCasts(); RHS = RHS->stripPointerCasts(); // A non-null pointer is not equal to a null pointer. if (llvm::isKnownNonNull(LHS, TLI) && isa(RHS) && (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_NE)) return ConstantInt::get(GetCompareTy(LHS), !CmpInst::isTrueWhenEqual(Pred)); // We can only fold certain predicates on pointer comparisons. switch (Pred) { default: return nullptr; // Equality comaprisons are easy to fold. case CmpInst::ICMP_EQ: case CmpInst::ICMP_NE: break; // We can only handle unsigned relational comparisons because 'inbounds' on // a GEP only protects against unsigned wrapping. case CmpInst::ICMP_UGT: case CmpInst::ICMP_UGE: case CmpInst::ICMP_ULT: case CmpInst::ICMP_ULE: // However, we have to switch them to their signed variants to handle // negative indices from the base pointer. Pred = ICmpInst::getSignedPredicate(Pred); break; } // Strip off any constant offsets so that we can reason about them. // It's tempting to use getUnderlyingObject or even just stripInBoundsOffsets // here and compare base addresses like AliasAnalysis does, however there are // numerous hazards. AliasAnalysis and its utilities rely on special rules // governing loads and stores which don't apply to icmps. Also, AliasAnalysis // doesn't need to guarantee pointer inequality when it says NoAlias. Constant *LHSOffset = stripAndComputeConstantOffsets(DL, LHS); Constant *RHSOffset = stripAndComputeConstantOffsets(DL, RHS); // If LHS and RHS are related via constant offsets to the same base // value, we can replace it with an icmp which just compares the offsets. if (LHS == RHS) return ConstantExpr::getICmp(Pred, LHSOffset, RHSOffset); // Various optimizations for (in)equality comparisons. if (Pred == CmpInst::ICMP_EQ || Pred == CmpInst::ICMP_NE) { // Different non-empty allocations that exist at the same time have // different addresses (if the program can tell). Global variables always // exist, so they always exist during the lifetime of each other and all // allocas. Two different allocas usually have different addresses... // // However, if there's an @llvm.stackrestore dynamically in between two // allocas, they may have the same address. It's tempting to reduce the // scope of the problem by only looking at *static* allocas here. That would // cover the majority of allocas while significantly reducing the likelihood // of having an @llvm.stackrestore pop up in the middle. However, it's not // actually impossible for an @llvm.stackrestore to pop up in the middle of // an entry block. Also, if we have a block that's not attached to a // function, we can't tell if it's "static" under the current definition. // Theoretically, this problem could be fixed by creating a new kind of // instruction kind specifically for static allocas. Such a new instruction // could be required to be at the top of the entry block, thus preventing it // from being subject to a @llvm.stackrestore. Instcombine could even // convert regular allocas into these special allocas. It'd be nifty. // However, until then, this problem remains open. // // So, we'll assume that two non-empty allocas have different addresses // for now. // // With all that, if the offsets are within the bounds of their allocations // (and not one-past-the-end! so we can't use inbounds!), and their // allocations aren't the same, the pointers are not equal. // // Note that it's not necessary to check for LHS being a global variable // address, due to canonicalization and constant folding. if (isa(LHS) && (isa(RHS) || isa(RHS))) { ConstantInt *LHSOffsetCI = dyn_cast(LHSOffset); ConstantInt *RHSOffsetCI = dyn_cast(RHSOffset); uint64_t LHSSize, RHSSize; if (LHSOffsetCI && RHSOffsetCI && getObjectSize(LHS, LHSSize, DL, TLI) && getObjectSize(RHS, RHSSize, DL, TLI)) { const APInt &LHSOffsetValue = LHSOffsetCI->getValue(); const APInt &RHSOffsetValue = RHSOffsetCI->getValue(); if (!LHSOffsetValue.isNegative() && !RHSOffsetValue.isNegative() && LHSOffsetValue.ult(LHSSize) && RHSOffsetValue.ult(RHSSize)) { return ConstantInt::get(GetCompareTy(LHS), !CmpInst::isTrueWhenEqual(Pred)); } } // Repeat the above check but this time without depending on DataLayout // or being able to compute a precise size. if (!cast(LHS->getType())->isEmptyTy() && !cast(RHS->getType())->isEmptyTy() && LHSOffset->isNullValue() && RHSOffset->isNullValue()) return ConstantInt::get(GetCompareTy(LHS), !CmpInst::isTrueWhenEqual(Pred)); } // Even if an non-inbounds GEP occurs along the path we can still optimize // equality comparisons concerning the result. We avoid walking the whole // chain again by starting where the last calls to // stripAndComputeConstantOffsets left off and accumulate the offsets. Constant *LHSNoBound = stripAndComputeConstantOffsets(DL, LHS, true); Constant *RHSNoBound = stripAndComputeConstantOffsets(DL, RHS, true); if (LHS == RHS) return ConstantExpr::getICmp(Pred, ConstantExpr::getAdd(LHSOffset, LHSNoBound), ConstantExpr::getAdd(RHSOffset, RHSNoBound)); // If one side of the equality comparison must come from a noalias call // (meaning a system memory allocation function), and the other side must // come from a pointer that cannot overlap with dynamically-allocated // memory within the lifetime of the current function (allocas, byval // arguments, globals), then determine the comparison result here. SmallVector LHSUObjs, RHSUObjs; GetUnderlyingObjects(LHS, LHSUObjs, DL); GetUnderlyingObjects(RHS, RHSUObjs, DL); // Is the set of underlying objects all noalias calls? auto IsNAC = [](SmallVectorImpl &Objects) { return std::all_of(Objects.begin(), Objects.end(), [](Value *V){ return isNoAliasCall(V); }); }; // Is the set of underlying objects all things which must be disjoint from // noalias calls. For allocas, we consider only static ones (dynamic // allocas might be transformed into calls to malloc not simultaneously // live with the compared-to allocation). For globals, we exclude symbols // that might be resolve lazily to symbols in another dynamically-loaded // library (and, thus, could be malloc'ed by the implementation). auto IsAllocDisjoint = [](SmallVectorImpl &Objects) { return std::all_of(Objects.begin(), Objects.end(), [](Value *V){ if (const AllocaInst *AI = dyn_cast(V)) return AI->getParent() && AI->getParent()->getParent() && AI->isStaticAlloca(); if (const GlobalValue *GV = dyn_cast(V)) return (GV->hasLocalLinkage() || GV->hasHiddenVisibility() || GV->hasProtectedVisibility() || GV->hasUnnamedAddr()) && !GV->isThreadLocal(); if (const Argument *A = dyn_cast(V)) return A->hasByValAttr(); return false; }); }; if ((IsNAC(LHSUObjs) && IsAllocDisjoint(RHSUObjs)) || (IsNAC(RHSUObjs) && IsAllocDisjoint(LHSUObjs))) return ConstantInt::get(GetCompareTy(LHS), !CmpInst::isTrueWhenEqual(Pred)); } // Otherwise, fail. return nullptr; } /// SimplifyICmpInst - Given operands for an ICmpInst, see if we can /// fold the result. If not, this returns null. static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; assert(CmpInst::isIntPredicate(Pred) && "Not an integer compare!"); if (Constant *CLHS = dyn_cast(LHS)) { if (Constant *CRHS = dyn_cast(RHS)) return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, Q.DL, Q.TLI); // If we have a constant, make sure it is on the RHS. std::swap(LHS, RHS); Pred = CmpInst::getSwappedPredicate(Pred); } Type *ITy = GetCompareTy(LHS); // The return type. Type *OpTy = LHS->getType(); // The operand type. // icmp X, X -> true/false // X icmp undef -> true/false. For example, icmp ugt %X, undef -> false // because X could be 0. if (LHS == RHS || isa(RHS)) return ConstantInt::get(ITy, CmpInst::isTrueWhenEqual(Pred)); // Special case logic when the operands have i1 type. if (OpTy->getScalarType()->isIntegerTy(1)) { switch (Pred) { default: break; case ICmpInst::ICMP_EQ: // X == 1 -> X if (match(RHS, m_One())) return LHS; break; case ICmpInst::ICMP_NE: // X != 0 -> X if (match(RHS, m_Zero())) return LHS; break; case ICmpInst::ICMP_UGT: // X >u 0 -> X if (match(RHS, m_Zero())) return LHS; break; case ICmpInst::ICMP_UGE: // X >=u 1 -> X if (match(RHS, m_One())) return LHS; break; case ICmpInst::ICMP_SLT: // X X if (match(RHS, m_Zero())) return LHS; break; case ICmpInst::ICMP_SLE: // X <=s -1 -> X if (match(RHS, m_One())) return LHS; break; } } // If we are comparing with zero then try hard since this is a common case. if (match(RHS, m_Zero())) { bool LHSKnownNonNegative, LHSKnownNegative; switch (Pred) { default: llvm_unreachable("Unknown ICmp predicate!"); case ICmpInst::ICMP_ULT: return getFalse(ITy); case ICmpInst::ICMP_UGE: return getTrue(ITy); case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: if (isKnownNonZero(LHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return getFalse(ITy); break; case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGT: if (isKnownNonZero(LHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return getTrue(ITy); break; case ICmpInst::ICMP_SLT: ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (LHSKnownNegative) return getTrue(ITy); if (LHSKnownNonNegative) return getFalse(ITy); break; case ICmpInst::ICMP_SLE: ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (LHSKnownNegative) return getTrue(ITy); if (LHSKnownNonNegative && isKnownNonZero(LHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return getFalse(ITy); break; case ICmpInst::ICMP_SGE: ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (LHSKnownNegative) return getFalse(ITy); if (LHSKnownNonNegative) return getTrue(ITy); break; case ICmpInst::ICMP_SGT: ComputeSignBit(LHS, LHSKnownNonNegative, LHSKnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (LHSKnownNegative) return getFalse(ITy); if (LHSKnownNonNegative && isKnownNonZero(LHS, Q.DL, 0, Q.AC, Q.CxtI, Q.DT)) return getTrue(ITy); break; } } // See if we are doing a comparison with a constant integer. if (ConstantInt *CI = dyn_cast(RHS)) { // Rule out tautological comparisons (eg., ult 0 or uge 0). ConstantRange RHS_CR = ICmpInst::makeConstantRange(Pred, CI->getValue()); if (RHS_CR.isEmptySet()) return ConstantInt::getFalse(CI->getContext()); if (RHS_CR.isFullSet()) return ConstantInt::getTrue(CI->getContext()); // Many binary operators with constant RHS have easy to compute constant // range. Use them to check whether the comparison is a tautology. unsigned Width = CI->getBitWidth(); APInt Lower = APInt(Width, 0); APInt Upper = APInt(Width, 0); ConstantInt *CI2; if (match(LHS, m_URem(m_Value(), m_ConstantInt(CI2)))) { // 'urem x, CI2' produces [0, CI2). Upper = CI2->getValue(); } else if (match(LHS, m_SRem(m_Value(), m_ConstantInt(CI2)))) { // 'srem x, CI2' produces (-|CI2|, |CI2|). Upper = CI2->getValue().abs(); Lower = (-Upper) + 1; } else if (match(LHS, m_UDiv(m_ConstantInt(CI2), m_Value()))) { // 'udiv CI2, x' produces [0, CI2]. Upper = CI2->getValue() + 1; } else if (match(LHS, m_UDiv(m_Value(), m_ConstantInt(CI2)))) { // 'udiv x, CI2' produces [0, UINT_MAX / CI2]. APInt NegOne = APInt::getAllOnesValue(Width); if (!CI2->isZero()) Upper = NegOne.udiv(CI2->getValue()) + 1; } else if (match(LHS, m_SDiv(m_ConstantInt(CI2), m_Value()))) { if (CI2->isMinSignedValue()) { // 'sdiv INT_MIN, x' produces [INT_MIN, INT_MIN / -2]. Lower = CI2->getValue(); Upper = Lower.lshr(1) + 1; } else { // 'sdiv CI2, x' produces [-|CI2|, |CI2|]. Upper = CI2->getValue().abs() + 1; Lower = (-Upper) + 1; } } else if (match(LHS, m_SDiv(m_Value(), m_ConstantInt(CI2)))) { APInt IntMin = APInt::getSignedMinValue(Width); APInt IntMax = APInt::getSignedMaxValue(Width); APInt Val = CI2->getValue(); if (Val.isAllOnesValue()) { // 'sdiv x, -1' produces [INT_MIN + 1, INT_MAX] // where CI2 != -1 and CI2 != 0 and CI2 != 1 Lower = IntMin + 1; Upper = IntMax + 1; } else if (Val.countLeadingZeros() < Width - 1) { // 'sdiv x, CI2' produces [INT_MIN / CI2, INT_MAX / CI2] // where CI2 != -1 and CI2 != 0 and CI2 != 1 Lower = IntMin.sdiv(Val); Upper = IntMax.sdiv(Val); if (Lower.sgt(Upper)) std::swap(Lower, Upper); Upper = Upper + 1; assert(Upper != Lower && "Upper part of range has wrapped!"); } } else if (match(LHS, m_NUWShl(m_ConstantInt(CI2), m_Value()))) { // 'shl nuw CI2, x' produces [CI2, CI2 << CLZ(CI2)] Lower = CI2->getValue(); Upper = Lower.shl(Lower.countLeadingZeros()) + 1; } else if (match(LHS, m_NSWShl(m_ConstantInt(CI2), m_Value()))) { if (CI2->isNegative()) { // 'shl nsw CI2, x' produces [CI2 << CLO(CI2)-1, CI2] unsigned ShiftAmount = CI2->getValue().countLeadingOnes() - 1; Lower = CI2->getValue().shl(ShiftAmount); Upper = CI2->getValue() + 1; } else { // 'shl nsw CI2, x' produces [CI2, CI2 << CLZ(CI2)-1] unsigned ShiftAmount = CI2->getValue().countLeadingZeros() - 1; Lower = CI2->getValue(); Upper = CI2->getValue().shl(ShiftAmount) + 1; } } else if (match(LHS, m_LShr(m_Value(), m_ConstantInt(CI2)))) { // 'lshr x, CI2' produces [0, UINT_MAX >> CI2]. APInt NegOne = APInt::getAllOnesValue(Width); if (CI2->getValue().ult(Width)) Upper = NegOne.lshr(CI2->getValue()) + 1; } else if (match(LHS, m_LShr(m_ConstantInt(CI2), m_Value()))) { // 'lshr CI2, x' produces [CI2 >> (Width-1), CI2]. unsigned ShiftAmount = Width - 1; if (!CI2->isZero() && cast(LHS)->isExact()) ShiftAmount = CI2->getValue().countTrailingZeros(); Lower = CI2->getValue().lshr(ShiftAmount); Upper = CI2->getValue() + 1; } else if (match(LHS, m_AShr(m_Value(), m_ConstantInt(CI2)))) { // 'ashr x, CI2' produces [INT_MIN >> CI2, INT_MAX >> CI2]. APInt IntMin = APInt::getSignedMinValue(Width); APInt IntMax = APInt::getSignedMaxValue(Width); if (CI2->getValue().ult(Width)) { Lower = IntMin.ashr(CI2->getValue()); Upper = IntMax.ashr(CI2->getValue()) + 1; } } else if (match(LHS, m_AShr(m_ConstantInt(CI2), m_Value()))) { unsigned ShiftAmount = Width - 1; if (!CI2->isZero() && cast(LHS)->isExact()) ShiftAmount = CI2->getValue().countTrailingZeros(); if (CI2->isNegative()) { // 'ashr CI2, x' produces [CI2, CI2 >> (Width-1)] Lower = CI2->getValue(); Upper = CI2->getValue().ashr(ShiftAmount) + 1; } else { // 'ashr CI2, x' produces [CI2 >> (Width-1), CI2] Lower = CI2->getValue().ashr(ShiftAmount); Upper = CI2->getValue() + 1; } } else if (match(LHS, m_Or(m_Value(), m_ConstantInt(CI2)))) { // 'or x, CI2' produces [CI2, UINT_MAX]. Lower = CI2->getValue(); } else if (match(LHS, m_And(m_Value(), m_ConstantInt(CI2)))) { // 'and x, CI2' produces [0, CI2]. Upper = CI2->getValue() + 1; } if (Lower != Upper) { ConstantRange LHS_CR = ConstantRange(Lower, Upper); if (RHS_CR.contains(LHS_CR)) return ConstantInt::getTrue(RHS->getContext()); if (RHS_CR.inverse().contains(LHS_CR)) return ConstantInt::getFalse(RHS->getContext()); } } // Compare of cast, for example (zext X) != 0 -> X != 0 if (isa(LHS) && (isa(RHS) || isa(RHS))) { Instruction *LI = cast(LHS); Value *SrcOp = LI->getOperand(0); Type *SrcTy = SrcOp->getType(); Type *DstTy = LI->getType(); // Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input // if the integer type is the same size as the pointer type. if (MaxRecurse && Q.DL && isa(LI) && Q.DL->getTypeSizeInBits(SrcTy) == DstTy->getPrimitiveSizeInBits()) { if (Constant *RHSC = dyn_cast(RHS)) { // Transfer the cast to the constant. if (Value *V = SimplifyICmpInst(Pred, SrcOp, ConstantExpr::getIntToPtr(RHSC, SrcTy), Q, MaxRecurse-1)) return V; } else if (PtrToIntInst *RI = dyn_cast(RHS)) { if (RI->getOperand(0)->getType() == SrcTy) // Compare without the cast. if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), Q, MaxRecurse-1)) return V; } } if (isa(LHS)) { // Turn icmp (zext X), (zext Y) into a compare of X and Y if they have the // same type. if (ZExtInst *RI = dyn_cast(RHS)) { if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) // Compare X and Y. Note that signed predicates become unsigned. if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), SrcOp, RI->getOperand(0), Q, MaxRecurse-1)) return V; } // Turn icmp (zext X), Cst into a compare of X and Cst if Cst is extended // too. If not, then try to deduce the result of the comparison. else if (ConstantInt *CI = dyn_cast(RHS)) { // Compute the constant that would happen if we truncated to SrcTy then // reextended to DstTy. Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); Constant *RExt = ConstantExpr::getCast(CastInst::ZExt, Trunc, DstTy); // If the re-extended constant didn't change then this is effectively // also a case of comparing two zero-extended values. if (RExt == CI && MaxRecurse) if (Value *V = SimplifyICmpInst(ICmpInst::getUnsignedPredicate(Pred), SrcOp, Trunc, Q, MaxRecurse-1)) return V; // Otherwise the upper bits of LHS are zero while RHS has a non-zero bit // there. Use this to work out the result of the comparison. if (RExt != CI) { switch (Pred) { default: llvm_unreachable("Unknown ICmp predicate!"); // LHS getContext()); case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_ULE: return ConstantInt::getTrue(CI->getContext()); // LHS is non-negative. If RHS is negative then LHS >s LHS. If RHS // is non-negative then LHS getValue().isNegative() ? ConstantInt::getTrue(CI->getContext()) : ConstantInt::getFalse(CI->getContext()); case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_SLE: return CI->getValue().isNegative() ? ConstantInt::getFalse(CI->getContext()) : ConstantInt::getTrue(CI->getContext()); } } } } if (isa(LHS)) { // Turn icmp (sext X), (sext Y) into a compare of X and Y if they have the // same type. if (SExtInst *RI = dyn_cast(RHS)) { if (MaxRecurse && SrcTy == RI->getOperand(0)->getType()) // Compare X and Y. Note that the predicate does not change. if (Value *V = SimplifyICmpInst(Pred, SrcOp, RI->getOperand(0), Q, MaxRecurse-1)) return V; } // Turn icmp (sext X), Cst into a compare of X and Cst if Cst is extended // too. If not, then try to deduce the result of the comparison. else if (ConstantInt *CI = dyn_cast(RHS)) { // Compute the constant that would happen if we truncated to SrcTy then // reextended to DstTy. Constant *Trunc = ConstantExpr::getTrunc(CI, SrcTy); Constant *RExt = ConstantExpr::getCast(CastInst::SExt, Trunc, DstTy); // If the re-extended constant didn't change then this is effectively // also a case of comparing two sign-extended values. if (RExt == CI && MaxRecurse) if (Value *V = SimplifyICmpInst(Pred, SrcOp, Trunc, Q, MaxRecurse-1)) return V; // Otherwise the upper bits of LHS are all equal, while RHS has varying // bits there. Use this to work out the result of the comparison. if (RExt != CI) { switch (Pred) { default: llvm_unreachable("Unknown ICmp predicate!"); case ICmpInst::ICMP_EQ: return ConstantInt::getFalse(CI->getContext()); case ICmpInst::ICMP_NE: return ConstantInt::getTrue(CI->getContext()); // If RHS is non-negative then LHS s RHS. case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_SGE: return CI->getValue().isNegative() ? ConstantInt::getTrue(CI->getContext()) : ConstantInt::getFalse(CI->getContext()); case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_SLE: return CI->getValue().isNegative() ? ConstantInt::getFalse(CI->getContext()) : ConstantInt::getTrue(CI->getContext()); // If LHS is non-negative then LHS u RHS. case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_UGE: // Comparison is true iff the LHS =s 0. if (MaxRecurse) if (Value *V = SimplifyICmpInst(ICmpInst::ICMP_SGE, SrcOp, Constant::getNullValue(SrcTy), Q, MaxRecurse-1)) return V; break; } } } } } // Special logic for binary operators. BinaryOperator *LBO = dyn_cast(LHS); BinaryOperator *RBO = dyn_cast(RHS); if (MaxRecurse && (LBO || RBO)) { // Analyze the case when either LHS or RHS is an add instruction. Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr; // LHS = A + B (or A and B are null); RHS = C + D (or C and D are null). bool NoLHSWrapProblem = false, NoRHSWrapProblem = false; if (LBO && LBO->getOpcode() == Instruction::Add) { A = LBO->getOperand(0); B = LBO->getOperand(1); NoLHSWrapProblem = ICmpInst::isEquality(Pred) || (CmpInst::isUnsigned(Pred) && LBO->hasNoUnsignedWrap()) || (CmpInst::isSigned(Pred) && LBO->hasNoSignedWrap()); } if (RBO && RBO->getOpcode() == Instruction::Add) { C = RBO->getOperand(0); D = RBO->getOperand(1); NoRHSWrapProblem = ICmpInst::isEquality(Pred) || (CmpInst::isUnsigned(Pred) && RBO->hasNoUnsignedWrap()) || (CmpInst::isSigned(Pred) && RBO->hasNoSignedWrap()); } // icmp (X+Y), X -> icmp Y, 0 for equalities or if there is no overflow. if ((A == RHS || B == RHS) && NoLHSWrapProblem) if (Value *V = SimplifyICmpInst(Pred, A == RHS ? B : A, Constant::getNullValue(RHS->getType()), Q, MaxRecurse-1)) return V; // icmp X, (X+Y) -> icmp 0, Y for equalities or if there is no overflow. if ((C == LHS || D == LHS) && NoRHSWrapProblem) if (Value *V = SimplifyICmpInst(Pred, Constant::getNullValue(LHS->getType()), C == LHS ? D : C, Q, MaxRecurse-1)) return V; // icmp (X+Y), (X+Z) -> icmp Y,Z for equalities or if there is no overflow. if (A && C && (A == C || A == D || B == C || B == D) && NoLHSWrapProblem && NoRHSWrapProblem) { // Determine Y and Z in the form icmp (X+Y), (X+Z). Value *Y, *Z; if (A == C) { // C + B == C + D -> B == D Y = B; Z = D; } else if (A == D) { // D + B == C + D -> B == C Y = B; Z = C; } else if (B == C) { // A + C == C + D -> A == D Y = A; Z = D; } else { assert(B == D); // A + D == C + D -> A == C Y = A; Z = C; } if (Value *V = SimplifyICmpInst(Pred, Y, Z, Q, MaxRecurse-1)) return V; } } // icmp pred (or X, Y), X if (LBO && match(LBO, m_CombineOr(m_Or(m_Value(), m_Specific(RHS)), m_Or(m_Specific(RHS), m_Value())))) { if (Pred == ICmpInst::ICMP_ULT) return getFalse(ITy); if (Pred == ICmpInst::ICMP_UGE) return getTrue(ITy); } // icmp pred X, (or X, Y) if (RBO && match(RBO, m_CombineOr(m_Or(m_Value(), m_Specific(LHS)), m_Or(m_Specific(LHS), m_Value())))) { if (Pred == ICmpInst::ICMP_ULE) return getTrue(ITy); if (Pred == ICmpInst::ICMP_UGT) return getFalse(ITy); } // icmp pred (and X, Y), X if (LBO && match(LBO, m_CombineOr(m_And(m_Value(), m_Specific(RHS)), m_And(m_Specific(RHS), m_Value())))) { if (Pred == ICmpInst::ICMP_UGT) return getFalse(ITy); if (Pred == ICmpInst::ICMP_ULE) return getTrue(ITy); } // icmp pred X, (and X, Y) if (RBO && match(RBO, m_CombineOr(m_And(m_Value(), m_Specific(LHS)), m_And(m_Specific(LHS), m_Value())))) { if (Pred == ICmpInst::ICMP_UGE) return getTrue(ITy); if (Pred == ICmpInst::ICMP_ULT) return getFalse(ITy); } // 0 - (zext X) pred C if (!CmpInst::isUnsigned(Pred) && match(LHS, m_Neg(m_ZExt(m_Value())))) { if (ConstantInt *RHSC = dyn_cast(RHS)) { if (RHSC->getValue().isStrictlyPositive()) { if (Pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue(RHSC->getContext()); if (Pred == ICmpInst::ICMP_SGE) return ConstantInt::getFalse(RHSC->getContext()); if (Pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(RHSC->getContext()); if (Pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(RHSC->getContext()); } if (RHSC->getValue().isNonNegative()) { if (Pred == ICmpInst::ICMP_SLE) return ConstantInt::getTrue(RHSC->getContext()); if (Pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse(RHSC->getContext()); } } } // icmp pred (urem X, Y), Y if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) { bool KnownNonNegative, KnownNegative; switch (Pred) { default: break; case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_SGE: ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (!KnownNonNegative) break; // fall-through case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_UGE: return getFalse(ITy); case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_SLE: ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (!KnownNonNegative) break; // fall-through case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_ULE: return getTrue(ITy); } } // icmp pred X, (urem Y, X) if (RBO && match(RBO, m_URem(m_Value(), m_Specific(LHS)))) { bool KnownNonNegative, KnownNegative; switch (Pred) { default: break; case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_SGE: ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (!KnownNonNegative) break; // fall-through case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_UGE: return getTrue(ITy); case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_SLE: ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.DL, 0, Q.AC, Q.CxtI, Q.DT); if (!KnownNonNegative) break; // fall-through case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_ULE: return getFalse(ITy); } } // x udiv y <=u x. if (LBO && match(LBO, m_UDiv(m_Specific(RHS), m_Value()))) { // icmp pred (X /u Y), X if (Pred == ICmpInst::ICMP_UGT) return getFalse(ITy); if (Pred == ICmpInst::ICMP_ULE) return getTrue(ITy); } // handle: // CI2 << X == CI // CI2 << X != CI // // where CI2 is a power of 2 and CI isn't if (auto *CI = dyn_cast(RHS)) { const APInt *CI2Val, *CIVal = &CI->getValue(); if (LBO && match(LBO, m_Shl(m_APInt(CI2Val), m_Value())) && CI2Val->isPowerOf2()) { if (!CIVal->isPowerOf2()) { // CI2 << X can equal zero in some circumstances, // this simplification is unsafe if CI is zero. // // We know it is safe if: // - The shift is nsw, we can't shift out the one bit. // - The shift is nuw, we can't shift out the one bit. // - CI2 is one // - CI isn't zero if (LBO->hasNoSignedWrap() || LBO->hasNoUnsignedWrap() || *CI2Val == 1 || !CI->isZero()) { if (Pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(RHS->getContext()); if (Pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(RHS->getContext()); } } if (CIVal->isSignBit() && *CI2Val == 1) { if (Pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse(RHS->getContext()); if (Pred == ICmpInst::ICMP_ULE) return ConstantInt::getTrue(RHS->getContext()); } } } if (MaxRecurse && LBO && RBO && LBO->getOpcode() == RBO->getOpcode() && LBO->getOperand(1) == RBO->getOperand(1)) { switch (LBO->getOpcode()) { default: break; case Instruction::UDiv: case Instruction::LShr: if (ICmpInst::isSigned(Pred)) break; // fall-through case Instruction::SDiv: case Instruction::AShr: if (!LBO->isExact() || !RBO->isExact()) break; if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), RBO->getOperand(0), Q, MaxRecurse-1)) return V; break; case Instruction::Shl: { bool NUW = LBO->hasNoUnsignedWrap() && RBO->hasNoUnsignedWrap(); bool NSW = LBO->hasNoSignedWrap() && RBO->hasNoSignedWrap(); if (!NUW && !NSW) break; if (!NSW && ICmpInst::isSigned(Pred)) break; if (Value *V = SimplifyICmpInst(Pred, LBO->getOperand(0), RBO->getOperand(0), Q, MaxRecurse-1)) return V; break; } } } // Simplify comparisons involving max/min. Value *A, *B; CmpInst::Predicate P = CmpInst::BAD_ICMP_PREDICATE; CmpInst::Predicate EqP; // Chosen so that "A == max/min(A,B)" iff "A EqP B". // Signed variants on "max(a,b)>=a -> true". if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { if (A != RHS) std::swap(A, B); // smax(A, B) pred A. EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B". // We analyze this as smax(A, B) pred A. P = Pred; } else if (match(RHS, m_SMax(m_Value(A), m_Value(B))) && (A == LHS || B == LHS)) { if (A != LHS) std::swap(A, B); // A pred smax(A, B). EqP = CmpInst::ICMP_SGE; // "A == smax(A, B)" iff "A sge B". // We analyze this as smax(A, B) swapped-pred A. P = CmpInst::getSwappedPredicate(Pred); } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { if (A != RHS) std::swap(A, B); // smin(A, B) pred A. EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B". // We analyze this as smax(-A, -B) swapped-pred -A. // Note that we do not need to actually form -A or -B thanks to EqP. P = CmpInst::getSwappedPredicate(Pred); } else if (match(RHS, m_SMin(m_Value(A), m_Value(B))) && (A == LHS || B == LHS)) { if (A != LHS) std::swap(A, B); // A pred smin(A, B). EqP = CmpInst::ICMP_SLE; // "A == smin(A, B)" iff "A sle B". // We analyze this as smax(-A, -B) pred -A. // Note that we do not need to actually form -A or -B thanks to EqP. P = Pred; } if (P != CmpInst::BAD_ICMP_PREDICATE) { // Cases correspond to "max(A, B) p A". switch (P) { default: break; case CmpInst::ICMP_EQ: case CmpInst::ICMP_SLE: // Equivalent to "A EqP B". This may be the same as the condition tested // in the max/min; if so, we can just return that. if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B)) return V; if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B)) return V; // Otherwise, see if "A EqP B" simplifies. if (MaxRecurse) if (Value *V = SimplifyICmpInst(EqP, A, B, Q, MaxRecurse-1)) return V; break; case CmpInst::ICMP_NE: case CmpInst::ICMP_SGT: { CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP); // Equivalent to "A InvEqP B". This may be the same as the condition // tested in the max/min; if so, we can just return that. if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B)) return V; if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B)) return V; // Otherwise, see if "A InvEqP B" simplifies. if (MaxRecurse) if (Value *V = SimplifyICmpInst(InvEqP, A, B, Q, MaxRecurse-1)) return V; break; } case CmpInst::ICMP_SGE: // Always true. return getTrue(ITy); case CmpInst::ICMP_SLT: // Always false. return getFalse(ITy); } } // Unsigned variants on "max(a,b)>=a -> true". P = CmpInst::BAD_ICMP_PREDICATE; if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { if (A != RHS) std::swap(A, B); // umax(A, B) pred A. EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B". // We analyze this as umax(A, B) pred A. P = Pred; } else if (match(RHS, m_UMax(m_Value(A), m_Value(B))) && (A == LHS || B == LHS)) { if (A != LHS) std::swap(A, B); // A pred umax(A, B). EqP = CmpInst::ICMP_UGE; // "A == umax(A, B)" iff "A uge B". // We analyze this as umax(A, B) swapped-pred A. P = CmpInst::getSwappedPredicate(Pred); } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) && (A == RHS || B == RHS)) { if (A != RHS) std::swap(A, B); // umin(A, B) pred A. EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B". // We analyze this as umax(-A, -B) swapped-pred -A. // Note that we do not need to actually form -A or -B thanks to EqP. P = CmpInst::getSwappedPredicate(Pred); } else if (match(RHS, m_UMin(m_Value(A), m_Value(B))) && (A == LHS || B == LHS)) { if (A != LHS) std::swap(A, B); // A pred umin(A, B). EqP = CmpInst::ICMP_ULE; // "A == umin(A, B)" iff "A ule B". // We analyze this as umax(-A, -B) pred -A. // Note that we do not need to actually form -A or -B thanks to EqP. P = Pred; } if (P != CmpInst::BAD_ICMP_PREDICATE) { // Cases correspond to "max(A, B) p A". switch (P) { default: break; case CmpInst::ICMP_EQ: case CmpInst::ICMP_ULE: // Equivalent to "A EqP B". This may be the same as the condition tested // in the max/min; if so, we can just return that. if (Value *V = ExtractEquivalentCondition(LHS, EqP, A, B)) return V; if (Value *V = ExtractEquivalentCondition(RHS, EqP, A, B)) return V; // Otherwise, see if "A EqP B" simplifies. if (MaxRecurse) if (Value *V = SimplifyICmpInst(EqP, A, B, Q, MaxRecurse-1)) return V; break; case CmpInst::ICMP_NE: case CmpInst::ICMP_UGT: { CmpInst::Predicate InvEqP = CmpInst::getInversePredicate(EqP); // Equivalent to "A InvEqP B". This may be the same as the condition // tested in the max/min; if so, we can just return that. if (Value *V = ExtractEquivalentCondition(LHS, InvEqP, A, B)) return V; if (Value *V = ExtractEquivalentCondition(RHS, InvEqP, A, B)) return V; // Otherwise, see if "A InvEqP B" simplifies. if (MaxRecurse) if (Value *V = SimplifyICmpInst(InvEqP, A, B, Q, MaxRecurse-1)) return V; break; } case CmpInst::ICMP_UGE: // Always true. return getTrue(ITy); case CmpInst::ICMP_ULT: // Always false. return getFalse(ITy); } } // Variants on "max(x,y) >= min(x,z)". Value *C, *D; if (match(LHS, m_SMax(m_Value(A), m_Value(B))) && match(RHS, m_SMin(m_Value(C), m_Value(D))) && (A == C || A == D || B == C || B == D)) { // max(x, ?) pred min(x, ?). if (Pred == CmpInst::ICMP_SGE) // Always true. return getTrue(ITy); if (Pred == CmpInst::ICMP_SLT) // Always false. return getFalse(ITy); } else if (match(LHS, m_SMin(m_Value(A), m_Value(B))) && match(RHS, m_SMax(m_Value(C), m_Value(D))) && (A == C || A == D || B == C || B == D)) { // min(x, ?) pred max(x, ?). if (Pred == CmpInst::ICMP_SLE) // Always true. return getTrue(ITy); if (Pred == CmpInst::ICMP_SGT) // Always false. return getFalse(ITy); } else if (match(LHS, m_UMax(m_Value(A), m_Value(B))) && match(RHS, m_UMin(m_Value(C), m_Value(D))) && (A == C || A == D || B == C || B == D)) { // max(x, ?) pred min(x, ?). if (Pred == CmpInst::ICMP_UGE) // Always true. return getTrue(ITy); if (Pred == CmpInst::ICMP_ULT) // Always false. return getFalse(ITy); } else if (match(LHS, m_UMin(m_Value(A), m_Value(B))) && match(RHS, m_UMax(m_Value(C), m_Value(D))) && (A == C || A == D || B == C || B == D)) { // min(x, ?) pred max(x, ?). if (Pred == CmpInst::ICMP_ULE) // Always true. return getTrue(ITy); if (Pred == CmpInst::ICMP_UGT) // Always false. return getFalse(ITy); } // Simplify comparisons of related pointers using a powerful, recursive // GEP-walk when we have target data available.. if (LHS->getType()->isPointerTy()) if (Constant *C = computePointerICmp(Q.DL, Q.TLI, Pred, LHS, RHS)) return C; if (GetElementPtrInst *GLHS = dyn_cast(LHS)) { if (GEPOperator *GRHS = dyn_cast(RHS)) { if (GLHS->getPointerOperand() == GRHS->getPointerOperand() && GLHS->hasAllConstantIndices() && GRHS->hasAllConstantIndices() && (ICmpInst::isEquality(Pred) || (GLHS->isInBounds() && GRHS->isInBounds() && Pred == ICmpInst::getSignedPredicate(Pred)))) { // The bases are equal and the indices are constant. Build a constant // expression GEP with the same indices and a null base pointer to see // what constant folding can make out of it. Constant *Null = Constant::getNullValue(GLHS->getPointerOperandType()); SmallVector IndicesLHS(GLHS->idx_begin(), GLHS->idx_end()); Constant *NewLHS = ConstantExpr::getGetElementPtr(Null, IndicesLHS); SmallVector IndicesRHS(GRHS->idx_begin(), GRHS->idx_end()); Constant *NewRHS = ConstantExpr::getGetElementPtr(Null, IndicesRHS); return ConstantExpr::getICmp(Pred, NewLHS, NewRHS); } } } // If a bit is known to be zero for A and known to be one for B, // then A and B cannot be equal. if (ICmpInst::isEquality(Pred)) { if (ConstantInt *CI = dyn_cast(RHS)) { uint32_t BitWidth = CI->getBitWidth(); APInt LHSKnownZero(BitWidth, 0); APInt LHSKnownOne(BitWidth, 0); computeKnownBits(LHS, LHSKnownZero, LHSKnownOne, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT); const APInt &RHSVal = CI->getValue(); if (((LHSKnownZero & RHSVal) != 0) || ((LHSKnownOne & ~RHSVal) != 0)) return Pred == ICmpInst::ICMP_EQ ? ConstantInt::getFalse(CI->getContext()) : ConstantInt::getTrue(CI->getContext()); } } // If the comparison is with the result of a select instruction, check whether // comparing with either branch of the select always yields the same value. if (isa(LHS) || isa(RHS)) if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, Q, MaxRecurse)) return V; // If the comparison is with the result of a phi instruction, check whether // doing the compare with each incoming phi value yields a common result. if (isa(LHS) || isa(RHS)) if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, Instruction *CxtI) { return ::SimplifyICmpInst(Predicate, LHS, RHS, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyFCmpInst - Given operands for an FCmpInst, see if we can /// fold the result. If not, this returns null. static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { CmpInst::Predicate Pred = (CmpInst::Predicate)Predicate; assert(CmpInst::isFPPredicate(Pred) && "Not an FP compare!"); if (Constant *CLHS = dyn_cast(LHS)) { if (Constant *CRHS = dyn_cast(RHS)) return ConstantFoldCompareInstOperands(Pred, CLHS, CRHS, Q.DL, Q.TLI); // If we have a constant, make sure it is on the RHS. std::swap(LHS, RHS); Pred = CmpInst::getSwappedPredicate(Pred); } // Fold trivial predicates. if (Pred == FCmpInst::FCMP_FALSE) return ConstantInt::get(GetCompareTy(LHS), 0); if (Pred == FCmpInst::FCMP_TRUE) return ConstantInt::get(GetCompareTy(LHS), 1); if (isa(RHS)) // fcmp pred X, undef -> undef return UndefValue::get(GetCompareTy(LHS)); // fcmp x,x -> true/false. Not all compares are foldable. if (LHS == RHS) { if (CmpInst::isTrueWhenEqual(Pred)) return ConstantInt::get(GetCompareTy(LHS), 1); if (CmpInst::isFalseWhenEqual(Pred)) return ConstantInt::get(GetCompareTy(LHS), 0); } // Handle fcmp with constant RHS if (Constant *RHSC = dyn_cast(RHS)) { // If the constant is a nan, see if we can fold the comparison based on it. if (ConstantFP *CFP = dyn_cast(RHSC)) { if (CFP->getValueAPF().isNaN()) { if (FCmpInst::isOrdered(Pred)) // True "if ordered and foo" return ConstantInt::getFalse(CFP->getContext()); assert(FCmpInst::isUnordered(Pred) && "Comparison must be either ordered or unordered!"); // True if unordered. return ConstantInt::getTrue(CFP->getContext()); } // Check whether the constant is an infinity. if (CFP->getValueAPF().isInfinity()) { if (CFP->getValueAPF().isNegative()) { switch (Pred) { case FCmpInst::FCMP_OLT: // No value is ordered and less than negative infinity. return ConstantInt::getFalse(CFP->getContext()); case FCmpInst::FCMP_UGE: // All values are unordered with or at least negative infinity. return ConstantInt::getTrue(CFP->getContext()); default: break; } } else { switch (Pred) { case FCmpInst::FCMP_OGT: // No value is ordered and greater than infinity. return ConstantInt::getFalse(CFP->getContext()); case FCmpInst::FCMP_ULE: // All values are unordered with and at most infinity. return ConstantInt::getTrue(CFP->getContext()); default: break; } } } if (CFP->getValueAPF().isZero()) { switch (Pred) { case FCmpInst::FCMP_UGE: if (CannotBeOrderedLessThanZero(LHS)) return ConstantInt::getTrue(CFP->getContext()); break; case FCmpInst::FCMP_OLT: if (CannotBeOrderedLessThanZero(LHS)) return ConstantInt::getFalse(CFP->getContext()); break; default: break; } } } } // If the comparison is with the result of a select instruction, check whether // comparing with either branch of the select always yields the same value. if (isa(LHS) || isa(RHS)) if (Value *V = ThreadCmpOverSelect(Pred, LHS, RHS, Q, MaxRecurse)) return V; // If the comparison is with the result of a phi instruction, check whether // doing the compare with each incoming phi value yields a common result. if (isa(LHS) || isa(RHS)) if (Value *V = ThreadCmpOverPHI(Pred, LHS, RHS, Q, MaxRecurse)) return V; return nullptr; } Value *llvm::SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyFCmpInst(Predicate, LHS, RHS, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifySelectInst - Given operands for a SelectInst, see if we can fold /// the result. If not, this returns null. static Value *SimplifySelectInst(Value *CondVal, Value *TrueVal, Value *FalseVal, const Query &Q, unsigned MaxRecurse) { // select true, X, Y -> X // select false, X, Y -> Y if (Constant *CB = dyn_cast(CondVal)) { if (CB->isAllOnesValue()) return TrueVal; if (CB->isNullValue()) return FalseVal; } // select C, X, X -> X if (TrueVal == FalseVal) return TrueVal; if (isa(CondVal)) { // select undef, X, Y -> X or Y if (isa(TrueVal)) return TrueVal; return FalseVal; } if (isa(TrueVal)) // select C, undef, X -> X return FalseVal; if (isa(FalseVal)) // select C, X, undef -> X return TrueVal; const auto *ICI = dyn_cast(CondVal); unsigned BitWidth = TrueVal->getType()->getScalarSizeInBits(); if (ICI && BitWidth) { ICmpInst::Predicate Pred = ICI->getPredicate(); APInt MinSignedValue = APInt::getSignBit(BitWidth); Value *X; const APInt *Y; bool TrueWhenUnset; bool IsBitTest = false; if (ICmpInst::isEquality(Pred) && match(ICI->getOperand(0), m_And(m_Value(X), m_APInt(Y))) && match(ICI->getOperand(1), m_Zero())) { IsBitTest = true; TrueWhenUnset = Pred == ICmpInst::ICMP_EQ; } else if (Pred == ICmpInst::ICMP_SLT && match(ICI->getOperand(1), m_Zero())) { X = ICI->getOperand(0); Y = &MinSignedValue; IsBitTest = true; TrueWhenUnset = false; } else if (Pred == ICmpInst::ICMP_SGT && match(ICI->getOperand(1), m_AllOnes())) { X = ICI->getOperand(0); Y = &MinSignedValue; IsBitTest = true; TrueWhenUnset = true; } if (IsBitTest) { const APInt *C; // (X & Y) == 0 ? X & ~Y : X --> X // (X & Y) != 0 ? X & ~Y : X --> X & ~Y if (FalseVal == X && match(TrueVal, m_And(m_Specific(X), m_APInt(C))) && *Y == ~*C) return TrueWhenUnset ? FalseVal : TrueVal; // (X & Y) == 0 ? X : X & ~Y --> X & ~Y // (X & Y) != 0 ? X : X & ~Y --> X if (TrueVal == X && match(FalseVal, m_And(m_Specific(X), m_APInt(C))) && *Y == ~*C) return TrueWhenUnset ? FalseVal : TrueVal; if (Y->isPowerOf2()) { // (X & Y) == 0 ? X | Y : X --> X | Y // (X & Y) != 0 ? X | Y : X --> X if (FalseVal == X && match(TrueVal, m_Or(m_Specific(X), m_APInt(C))) && *Y == *C) return TrueWhenUnset ? TrueVal : FalseVal; // (X & Y) == 0 ? X : X | Y --> X // (X & Y) != 0 ? X : X | Y --> X | Y if (TrueVal == X && match(FalseVal, m_Or(m_Specific(X), m_APInt(C))) && *Y == *C) return TrueWhenUnset ? TrueVal : FalseVal; } } } return nullptr; } Value *llvm::SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifySelectInst(Cond, TrueVal, FalseVal, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyGEPInst - Given operands for an GetElementPtrInst, see if we can /// fold the result. If not, this returns null. static Value *SimplifyGEPInst(ArrayRef Ops, const Query &Q, unsigned) { // The type of the GEP pointer operand. PointerType *PtrTy = cast(Ops[0]->getType()->getScalarType()); unsigned AS = PtrTy->getAddressSpace(); // getelementptr P -> P. if (Ops.size() == 1) return Ops[0]; // Compute the (pointer) type returned by the GEP instruction. Type *LastType = GetElementPtrInst::getIndexedType(PtrTy, Ops.slice(1)); Type *GEPTy = PointerType::get(LastType, AS); if (VectorType *VT = dyn_cast(Ops[0]->getType())) GEPTy = VectorType::get(GEPTy, VT->getNumElements()); if (isa(Ops[0])) return UndefValue::get(GEPTy); if (Ops.size() == 2) { // getelementptr P, 0 -> P. if (match(Ops[1], m_Zero())) return Ops[0]; Type *Ty = PtrTy->getElementType(); if (Q.DL && Ty->isSized()) { Value *P; uint64_t C; uint64_t TyAllocSize = Q.DL->getTypeAllocSize(Ty); // getelementptr P, N -> P if P points to a type of zero size. if (TyAllocSize == 0) return Ops[0]; // The following transforms are only safe if the ptrtoint cast // doesn't truncate the pointers. if (Ops[1]->getType()->getScalarSizeInBits() == Q.DL->getPointerSizeInBits(AS)) { auto PtrToIntOrZero = [GEPTy](Value *P) -> Value * { if (match(P, m_Zero())) return Constant::getNullValue(GEPTy); Value *Temp; if (match(P, m_PtrToInt(m_Value(Temp)))) if (Temp->getType() == GEPTy) return Temp; return nullptr; }; // getelementptr V, (sub P, V) -> P if P points to a type of size 1. if (TyAllocSize == 1 && match(Ops[1], m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))))) if (Value *R = PtrToIntOrZero(P)) return R; // getelementptr V, (ashr (sub P, V), C) -> Q // if P points to a type of size 1 << C. if (match(Ops[1], m_AShr(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))), m_ConstantInt(C))) && TyAllocSize == 1ULL << C) if (Value *R = PtrToIntOrZero(P)) return R; // getelementptr V, (sdiv (sub P, V), C) -> Q // if P points to a type of size C. if (match(Ops[1], m_SDiv(m_Sub(m_Value(P), m_PtrToInt(m_Specific(Ops[0]))), m_SpecificInt(TyAllocSize)))) if (Value *R = PtrToIntOrZero(P)) return R; } } } // Check to see if this is constant foldable. for (unsigned i = 0, e = Ops.size(); i != e; ++i) if (!isa(Ops[i])) return nullptr; return ConstantExpr::getGetElementPtr(cast(Ops[0]), Ops.slice(1)); } Value *llvm::SimplifyGEPInst(ArrayRef Ops, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyGEPInst(Ops, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyInsertValueInst - Given operands for an InsertValueInst, see if we /// can fold the result. If not, this returns null. static Value *SimplifyInsertValueInst(Value *Agg, Value *Val, ArrayRef Idxs, const Query &Q, unsigned) { if (Constant *CAgg = dyn_cast(Agg)) if (Constant *CVal = dyn_cast(Val)) return ConstantFoldInsertValueInstruction(CAgg, CVal, Idxs); // insertvalue x, undef, n -> x if (match(Val, m_Undef())) return Agg; // insertvalue x, (extractvalue y, n), n if (ExtractValueInst *EV = dyn_cast(Val)) if (EV->getAggregateOperand()->getType() == Agg->getType() && EV->getIndices() == Idxs) { // insertvalue undef, (extractvalue y, n), n -> y if (match(Agg, m_Undef())) return EV->getAggregateOperand(); // insertvalue y, (extractvalue y, n), n -> y if (Agg == EV->getAggregateOperand()) return Agg; } return nullptr; } Value *llvm::SimplifyInsertValueInst( Value *Agg, Value *Val, ArrayRef Idxs, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyInsertValueInst(Agg, Val, Idxs, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyPHINode - See if we can fold the given phi. If not, returns null. static Value *SimplifyPHINode(PHINode *PN, const Query &Q) { // If all of the PHI's incoming values are the same then replace the PHI node // with the common value. Value *CommonValue = nullptr; bool HasUndefInput = false; for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { Value *Incoming = PN->getIncomingValue(i); // If the incoming value is the phi node itself, it can safely be skipped. if (Incoming == PN) continue; if (isa(Incoming)) { // Remember that we saw an undef value, but otherwise ignore them. HasUndefInput = true; continue; } if (CommonValue && Incoming != CommonValue) return nullptr; // Not the same, bail out. CommonValue = Incoming; } // If CommonValue is null then all of the incoming values were either undef or // equal to the phi node itself. if (!CommonValue) return UndefValue::get(PN->getType()); // If we have a PHI node like phi(X, undef, X), where X is defined by some // instruction, we cannot return X as the result of the PHI node unless it // dominates the PHI block. if (HasUndefInput) return ValueDominatesPHI(CommonValue, PN, Q.DT) ? CommonValue : nullptr; return CommonValue; } static Value *SimplifyTruncInst(Value *Op, Type *Ty, const Query &Q, unsigned) { if (Constant *C = dyn_cast(Op)) return ConstantFoldInstOperands(Instruction::Trunc, Ty, C, Q.DL, Q.TLI); return nullptr; } Value *llvm::SimplifyTruncInst(Value *Op, Type *Ty, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyTruncInst(Op, Ty, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } //=== Helper functions for higher up the class hierarchy. /// SimplifyBinOp - Given operands for a BinaryOperator, see if we can /// fold the result. If not, this returns null. static Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { switch (Opcode) { case Instruction::Add: return SimplifyAddInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, Q, MaxRecurse); case Instruction::FAdd: return SimplifyFAddInst(LHS, RHS, FastMathFlags(), Q, MaxRecurse); case Instruction::Sub: return SimplifySubInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, Q, MaxRecurse); case Instruction::FSub: return SimplifyFSubInst(LHS, RHS, FastMathFlags(), Q, MaxRecurse); case Instruction::Mul: return SimplifyMulInst (LHS, RHS, Q, MaxRecurse); case Instruction::FMul: return SimplifyFMulInst (LHS, RHS, FastMathFlags(), Q, MaxRecurse); case Instruction::SDiv: return SimplifySDivInst(LHS, RHS, Q, MaxRecurse); case Instruction::UDiv: return SimplifyUDivInst(LHS, RHS, Q, MaxRecurse); case Instruction::FDiv: return SimplifyFDivInst(LHS, RHS, Q, MaxRecurse); case Instruction::SRem: return SimplifySRemInst(LHS, RHS, Q, MaxRecurse); case Instruction::URem: return SimplifyURemInst(LHS, RHS, Q, MaxRecurse); case Instruction::FRem: return SimplifyFRemInst(LHS, RHS, Q, MaxRecurse); case Instruction::Shl: return SimplifyShlInst(LHS, RHS, /*isNSW*/false, /*isNUW*/false, Q, MaxRecurse); case Instruction::LShr: return SimplifyLShrInst(LHS, RHS, /*isExact*/false, Q, MaxRecurse); case Instruction::AShr: return SimplifyAShrInst(LHS, RHS, /*isExact*/false, Q, MaxRecurse); case Instruction::And: return SimplifyAndInst(LHS, RHS, Q, MaxRecurse); case Instruction::Or: return SimplifyOrInst (LHS, RHS, Q, MaxRecurse); case Instruction::Xor: return SimplifyXorInst(LHS, RHS, Q, MaxRecurse); default: if (Constant *CLHS = dyn_cast(LHS)) if (Constant *CRHS = dyn_cast(RHS)) { Constant *COps[] = {CLHS, CRHS}; return ConstantFoldInstOperands(Opcode, LHS->getType(), COps, Q.DL, Q.TLI); } // If the operation is associative, try some generic simplifications. if (Instruction::isAssociative(Opcode)) if (Value *V = SimplifyAssociativeBinOp(Opcode, LHS, RHS, Q, MaxRecurse)) return V; // If the operation is with the result of a select instruction check whether // operating on either branch of the select always yields the same value. if (isa(LHS) || isa(RHS)) if (Value *V = ThreadBinOpOverSelect(Opcode, LHS, RHS, Q, MaxRecurse)) return V; // If the operation is with the result of a phi instruction, check whether // operating on all incoming values of the phi always yields the same value. if (isa(LHS) || isa(RHS)) if (Value *V = ThreadBinOpOverPHI(Opcode, LHS, RHS, Q, MaxRecurse)) return V; return nullptr; } } Value *llvm::SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyBinOp(Opcode, LHS, RHS, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyCmpInst - Given operands for a CmpInst, see if we can /// fold the result. static Value *SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, const Query &Q, unsigned MaxRecurse) { if (CmpInst::isIntPredicate((CmpInst::Predicate)Predicate)) return SimplifyICmpInst(Predicate, LHS, RHS, Q, MaxRecurse); return SimplifyFCmpInst(Predicate, LHS, RHS, Q, MaxRecurse); } Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyCmpInst(Predicate, LHS, RHS, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } static bool IsIdempotent(Intrinsic::ID ID) { switch (ID) { default: return false; // Unary idempotent: f(f(x)) = f(x) case Intrinsic::fabs: case Intrinsic::floor: case Intrinsic::ceil: case Intrinsic::trunc: case Intrinsic::rint: case Intrinsic::nearbyint: case Intrinsic::round: return true; } } template static Value *SimplifyIntrinsic(Intrinsic::ID IID, IterTy ArgBegin, IterTy ArgEnd, const Query &Q, unsigned MaxRecurse) { // Perform idempotent optimizations if (!IsIdempotent(IID)) return nullptr; // Unary Ops if (std::distance(ArgBegin, ArgEnd) == 1) if (IntrinsicInst *II = dyn_cast(*ArgBegin)) if (II->getIntrinsicID() == IID) return II; return nullptr; } template static Value *SimplifyCall(Value *V, IterTy ArgBegin, IterTy ArgEnd, const Query &Q, unsigned MaxRecurse) { Type *Ty = V->getType(); if (PointerType *PTy = dyn_cast(Ty)) Ty = PTy->getElementType(); FunctionType *FTy = cast(Ty); // call undef -> undef if (isa(V)) return UndefValue::get(FTy->getReturnType()); Function *F = dyn_cast(V); if (!F) return nullptr; if (unsigned IID = F->getIntrinsicID()) if (Value *Ret = SimplifyIntrinsic((Intrinsic::ID) IID, ArgBegin, ArgEnd, Q, MaxRecurse)) return Ret; if (!canConstantFoldCallTo(F)) return nullptr; SmallVector ConstantArgs; ConstantArgs.reserve(ArgEnd - ArgBegin); for (IterTy I = ArgBegin, E = ArgEnd; I != E; ++I) { Constant *C = dyn_cast(*I); if (!C) return nullptr; ConstantArgs.push_back(C); } return ConstantFoldCall(F, ConstantArgs, Q.TLI); } Value *llvm::SimplifyCall(Value *V, User::op_iterator ArgBegin, User::op_iterator ArgEnd, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyCall(V, ArgBegin, ArgEnd, Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } Value *llvm::SimplifyCall(Value *V, ArrayRef Args, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC, const Instruction *CxtI) { return ::SimplifyCall(V, Args.begin(), Args.end(), Query(DL, TLI, DT, AC, CxtI), RecursionLimit); } /// SimplifyInstruction - See if we can compute a simplified version of this /// instruction. If not, this returns null. Value *llvm::SimplifyInstruction(Instruction *I, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC) { Value *Result; switch (I->getOpcode()) { default: Result = ConstantFoldInstruction(I, DL, TLI); break; case Instruction::FAdd: Result = SimplifyFAddInst(I->getOperand(0), I->getOperand(1), I->getFastMathFlags(), DL, TLI, DT, AC, I); break; case Instruction::Add: Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1), cast(I)->hasNoSignedWrap(), cast(I)->hasNoUnsignedWrap(), DL, TLI, DT, AC, I); break; case Instruction::FSub: Result = SimplifyFSubInst(I->getOperand(0), I->getOperand(1), I->getFastMathFlags(), DL, TLI, DT, AC, I); break; case Instruction::Sub: Result = SimplifySubInst(I->getOperand(0), I->getOperand(1), cast(I)->hasNoSignedWrap(), cast(I)->hasNoUnsignedWrap(), DL, TLI, DT, AC, I); break; case Instruction::FMul: Result = SimplifyFMulInst(I->getOperand(0), I->getOperand(1), I->getFastMathFlags(), DL, TLI, DT, AC, I); break; case Instruction::Mul: Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::SDiv: Result = SimplifySDivInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::UDiv: Result = SimplifyUDivInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::FDiv: Result = SimplifyFDivInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::SRem: Result = SimplifySRemInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::URem: Result = SimplifyURemInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::FRem: Result = SimplifyFRemInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::Shl: Result = SimplifyShlInst(I->getOperand(0), I->getOperand(1), cast(I)->hasNoSignedWrap(), cast(I)->hasNoUnsignedWrap(), DL, TLI, DT, AC, I); break; case Instruction::LShr: Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1), cast(I)->isExact(), DL, TLI, DT, AC, I); break; case Instruction::AShr: Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1), cast(I)->isExact(), DL, TLI, DT, AC, I); break; case Instruction::And: Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::Or: Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::Xor: Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::ICmp: Result = SimplifyICmpInst(cast(I)->getPredicate(), I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::FCmp: Result = SimplifyFCmpInst(cast(I)->getPredicate(), I->getOperand(0), I->getOperand(1), DL, TLI, DT, AC, I); break; case Instruction::Select: Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1), I->getOperand(2), DL, TLI, DT, AC, I); break; case Instruction::GetElementPtr: { SmallVector Ops(I->op_begin(), I->op_end()); Result = SimplifyGEPInst(Ops, DL, TLI, DT, AC, I); break; } case Instruction::InsertValue: { InsertValueInst *IV = cast(I); Result = SimplifyInsertValueInst(IV->getAggregateOperand(), IV->getInsertedValueOperand(), IV->getIndices(), DL, TLI, DT, AC, I); break; } case Instruction::PHI: Result = SimplifyPHINode(cast(I), Query(DL, TLI, DT, AC, I)); break; case Instruction::Call: { CallSite CS(cast(I)); Result = SimplifyCall(CS.getCalledValue(), CS.arg_begin(), CS.arg_end(), DL, TLI, DT, AC, I); break; } case Instruction::Trunc: Result = SimplifyTruncInst(I->getOperand(0), I->getType(), DL, TLI, DT, AC, I); break; } /// If called on unreachable code, the above logic may report that the /// instruction simplified to itself. Make life easier for users by /// detecting that case here, returning a safe value instead. return Result == I ? UndefValue::get(I->getType()) : Result; } /// \brief Implementation of recursive simplification through an instructions /// uses. /// /// This is the common implementation of the recursive simplification routines. /// If we have a pre-simplified value in 'SimpleV', that is forcibly used to /// replace the instruction 'I'. Otherwise, we simply add 'I' to the list of /// instructions to process and attempt to simplify it using /// InstructionSimplify. /// /// This routine returns 'true' only when *it* simplifies something. The passed /// in simplified value does not count toward this. static bool replaceAndRecursivelySimplifyImpl(Instruction *I, Value *SimpleV, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC) { bool Simplified = false; SmallSetVector Worklist; // If we have an explicit value to collapse to, do that round of the // simplification loop by hand initially. if (SimpleV) { for (User *U : I->users()) if (U != I) Worklist.insert(cast(U)); // Replace the instruction with its simplified value. I->replaceAllUsesWith(SimpleV); // Gracefully handle edge cases where the instruction is not wired into any // parent block. if (I->getParent()) I->eraseFromParent(); } else { Worklist.insert(I); } // Note that we must test the size on each iteration, the worklist can grow. for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) { I = Worklist[Idx]; // See if this instruction simplifies. SimpleV = SimplifyInstruction(I, DL, TLI, DT, AC); if (!SimpleV) continue; Simplified = true; // Stash away all the uses of the old instruction so we can check them for // recursive simplifications after a RAUW. This is cheaper than checking all // uses of To on the recursive step in most cases. for (User *U : I->users()) Worklist.insert(cast(U)); // Replace the instruction with its simplified value. I->replaceAllUsesWith(SimpleV); // Gracefully handle edge cases where the instruction is not wired into any // parent block. if (I->getParent()) I->eraseFromParent(); } return Simplified; } bool llvm::recursivelySimplifyInstruction(Instruction *I, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC) { return replaceAndRecursivelySimplifyImpl(I, nullptr, DL, TLI, DT, AC); } bool llvm::replaceAndRecursivelySimplify(Instruction *I, Value *SimpleV, const DataLayout *DL, const TargetLibraryInfo *TLI, const DominatorTree *DT, AssumptionCache *AC) { assert(I != SimpleV && "replaceAndRecursivelySimplify(X,X) is not valid!"); assert(SimpleV && "Must provide a simplified value."); return replaceAndRecursivelySimplifyImpl(I, SimpleV, DL, TLI, DT, AC); }