From: Tom Weaver Date: Mon, 11 Nov 2019 13:47:13 +0000 (+0000) Subject: [DBG][OPT] Attempt to salvage or undef debug info when removing trivially deletable... X-Git-Tag: llvmorg-11-init~4556 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=1984a27db58e9053371ab6d6dc288c81c8a071ac;p=platform%2Fupstream%2Fllvm.git [DBG][OPT] Attempt to salvage or undef debug info when removing trivially deletable instructions in the Reassociate Expression pass. Reviewed By: aprantl, vsk Differential revision: https://reviews.llvm.org/D69943 --- diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp.rej b/llvm/lib/Transforms/Scalar/Reassociate.cpp.rej new file mode 100644 index 000000000000..83c547675403 --- /dev/null +++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp.rej @@ -0,0 +1,2506 @@ +--- llvm/lib/Transforms/Scalar/Reassociate.cpp ++++ llvm/lib/Transforms/Scalar/Reassociate.cpp +@@ -1,2501 +1,2503 @@ + //===- Reassociate.cpp - Reassociate binary expressions -------------------===// + // + // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. + // See https://llvm.org/LICENSE.txt for license information. + // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception + // + //===----------------------------------------------------------------------===// + // + // This pass reassociates commutative expressions in an order that is designed + // to promote better constant propagation, GCSE, LICM, PRE, etc. + // + // For example: 4 + (x + 5) -> x + (4 + 5) + // + // In the implementation of this algorithm, constants are assigned rank = 0, + // function arguments are rank = 1, and other values are assigned ranks + // corresponding to the reverse post order traversal of current function + // (starting at 2), which effectively gives values in deep loops higher rank + // than values not in loops. + // + //===----------------------------------------------------------------------===// + + #include "llvm/Transforms/Scalar/Reassociate.h" + #include "llvm/ADT/APFloat.h" + #include "llvm/ADT/APInt.h" + #include "llvm/ADT/DenseMap.h" + #include "llvm/ADT/PostOrderIterator.h" + #include "llvm/ADT/SetVector.h" + #include "llvm/ADT/SmallPtrSet.h" + #include "llvm/ADT/SmallSet.h" + #include "llvm/ADT/SmallVector.h" + #include "llvm/ADT/Statistic.h" + #include "llvm/Analysis/GlobalsModRef.h" + #include "llvm/Transforms/Utils/Local.h" + #include "llvm/Analysis/ValueTracking.h" + #include "llvm/IR/Argument.h" + #include "llvm/IR/BasicBlock.h" + #include "llvm/IR/CFG.h" + #include "llvm/IR/Constant.h" + #include "llvm/IR/Constants.h" + #include "llvm/IR/Function.h" + #include "llvm/IR/IRBuilder.h" + #include "llvm/IR/InstrTypes.h" + #include "llvm/IR/Instruction.h" + #include "llvm/IR/Instructions.h" + #include "llvm/IR/IntrinsicInst.h" + #include "llvm/IR/Operator.h" + #include "llvm/IR/PassManager.h" + #include "llvm/IR/PatternMatch.h" + #include "llvm/IR/Type.h" + #include "llvm/IR/User.h" + #include "llvm/IR/Value.h" + #include "llvm/IR/ValueHandle.h" + #include "llvm/Pass.h" + #include "llvm/Support/Casting.h" + #include "llvm/Support/Debug.h" + #include "llvm/Support/ErrorHandling.h" + #include "llvm/Support/raw_ostream.h" + #include "llvm/Transforms/Scalar.h" + #include + #include + #include + + using namespace llvm; + using namespace reassociate; + using namespace PatternMatch; + + #define DEBUG_TYPE "reassociate" + + STATISTIC(NumChanged, "Number of insts reassociated"); + STATISTIC(NumAnnihil, "Number of expr tree annihilated"); + STATISTIC(NumFactor , "Number of multiplies factored"); + + #ifndef NDEBUG + /// Print out the expression identified in the Ops list. + static void PrintOps(Instruction *I, const SmallVectorImpl &Ops) { + Module *M = I->getModule(); + dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " " + << *Ops[0].Op->getType() << '\t'; + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + dbgs() << "[ "; + Ops[i].Op->printAsOperand(dbgs(), false, M); + dbgs() << ", #" << Ops[i].Rank << "] "; + } + } + #endif + + /// Utility class representing a non-constant Xor-operand. We classify + /// non-constant Xor-Operands into two categories: + /// C1) The operand is in the form "X & C", where C is a constant and C != ~0 + /// C2) + /// C2.1) The operand is in the form of "X | C", where C is a non-zero + /// constant. + /// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this + /// operand as "E | 0" + class llvm::reassociate::XorOpnd { + public: + XorOpnd(Value *V); + + bool isInvalid() const { return SymbolicPart == nullptr; } + bool isOrExpr() const { return isOr; } + Value *getValue() const { return OrigVal; } + Value *getSymbolicPart() const { return SymbolicPart; } + unsigned getSymbolicRank() const { return SymbolicRank; } + const APInt &getConstPart() const { return ConstPart; } + + void Invalidate() { SymbolicPart = OrigVal = nullptr; } + void setSymbolicRank(unsigned R) { SymbolicRank = R; } + + private: + Value *OrigVal; + Value *SymbolicPart; + APInt ConstPart; + unsigned SymbolicRank; + bool isOr; + }; + + XorOpnd::XorOpnd(Value *V) { + assert(!isa(V) && "No ConstantInt"); + OrigVal = V; + Instruction *I = dyn_cast(V); + SymbolicRank = 0; + + if (I && (I->getOpcode() == Instruction::Or || + I->getOpcode() == Instruction::And)) { + Value *V0 = I->getOperand(0); + Value *V1 = I->getOperand(1); + const APInt *C; + if (match(V0, m_APInt(C))) + std::swap(V0, V1); + + if (match(V1, m_APInt(C))) { + ConstPart = *C; + SymbolicPart = V0; + isOr = (I->getOpcode() == Instruction::Or); + return; + } + } + + // view the operand as "V | 0" + SymbolicPart = V; + ConstPart = APInt::getNullValue(V->getType()->getScalarSizeInBits()); + isOr = true; + } + + /// Return true if V is an instruction of the specified opcode and if it + /// only has one use. + static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) { + auto *I = dyn_cast(V); + if (I && I->hasOneUse() && I->getOpcode() == Opcode) + if (!isa(I) || I->isFast()) + return cast(I); + return nullptr; + } + + static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1, + unsigned Opcode2) { + auto *I = dyn_cast(V); + if (I && I->hasOneUse() && + (I->getOpcode() == Opcode1 || I->getOpcode() == Opcode2)) + if (!isa(I) || I->isFast()) + return cast(I); + return nullptr; + } + + void ReassociatePass::BuildRankMap(Function &F, + ReversePostOrderTraversal &RPOT) { + unsigned Rank = 2; + + // Assign distinct ranks to function arguments. + for (auto &Arg : F.args()) { + ValueRankMap[&Arg] = ++Rank; + LLVM_DEBUG(dbgs() << "Calculated Rank[" << Arg.getName() << "] = " << Rank + << "\n"); + } + + // Traverse basic blocks in ReversePostOrder + for (BasicBlock *BB : RPOT) { + unsigned BBRank = RankMap[BB] = ++Rank << 16; + + // Walk the basic block, adding precomputed ranks for any instructions that + // we cannot move. This ensures that the ranks for these instructions are + // all different in the block. + for (Instruction &I : *BB) + if (mayBeMemoryDependent(I)) + ValueRankMap[&I] = ++BBRank; + } + } + + unsigned ReassociatePass::getRank(Value *V) { + Instruction *I = dyn_cast(V); + if (!I) { + if (isa(V)) return ValueRankMap[V]; // Function argument. + return 0; // Otherwise it's a global or constant, rank 0. + } + + if (unsigned Rank = ValueRankMap[I]) + return Rank; // Rank already known? + + // If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that + // we can reassociate expressions for code motion! Since we do not recurse + // for PHI nodes, we cannot have infinite recursion here, because there + // cannot be loops in the value graph that do not go through PHI nodes. + unsigned Rank = 0, MaxRank = RankMap[I->getParent()]; + for (unsigned i = 0, e = I->getNumOperands(); i != e && Rank != MaxRank; ++i) + Rank = std::max(Rank, getRank(I->getOperand(i))); + + // If this is a 'not' or 'neg' instruction, do not count it for rank. This + // assures us that X and ~X will have the same rank. + if (!match(I, m_Not(m_Value())) && !match(I, m_Neg(m_Value())) && + !match(I, m_FNeg(m_Value()))) + ++Rank; + + LLVM_DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = " << Rank + << "\n"); + + return ValueRankMap[I] = Rank; + } + + // Canonicalize constants to RHS. Otherwise, sort the operands by rank. + void ReassociatePass::canonicalizeOperands(Instruction *I) { + assert(isa(I) && "Expected binary operator."); + assert(I->isCommutative() && "Expected commutative operator."); + + Value *LHS = I->getOperand(0); + Value *RHS = I->getOperand(1); + if (LHS == RHS || isa(RHS)) + return; + if (isa(LHS) || getRank(RHS) < getRank(LHS)) + cast(I)->swapOperands(); + } + + static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name, + Instruction *InsertBefore, Value *FlagsOp) { + if (S1->getType()->isIntOrIntVectorTy()) + return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore); + else { + BinaryOperator *Res = + BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore); + Res->setFastMathFlags(cast(FlagsOp)->getFastMathFlags()); + return Res; + } + } + + static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name, + Instruction *InsertBefore, Value *FlagsOp) { + if (S1->getType()->isIntOrIntVectorTy()) + return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore); + else { + BinaryOperator *Res = + BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore); + Res->setFastMathFlags(cast(FlagsOp)->getFastMathFlags()); + return Res; + } + } + + static BinaryOperator *CreateNeg(Value *S1, const Twine &Name, + Instruction *InsertBefore, Value *FlagsOp) { + if (S1->getType()->isIntOrIntVectorTy()) + return BinaryOperator::CreateNeg(S1, Name, InsertBefore); + else { + BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore); + Res->setFastMathFlags(cast(FlagsOp)->getFastMathFlags()); + return Res; + } + } + + /// Replace 0-X with X*-1. + static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) { + assert((isa(Neg) || isa(Neg)) && + "Expected a Negate!"); + // FIXME: It's not safe to lower a unary FNeg into a FMul by -1.0. + unsigned OpNo = isa(Neg) ? 1 : 0; + Type *Ty = Neg->getType(); + Constant *NegOne = Ty->isIntOrIntVectorTy() ? + ConstantInt::getAllOnesValue(Ty) : ConstantFP::get(Ty, -1.0); + + BinaryOperator *Res = CreateMul(Neg->getOperand(OpNo), NegOne, "", Neg, Neg); + Neg->setOperand(OpNo, Constant::getNullValue(Ty)); // Drop use of op. + Res->takeName(Neg); + Neg->replaceAllUsesWith(Res); + Res->setDebugLoc(Neg->getDebugLoc()); + return Res; + } + + /// Returns k such that lambda(2^Bitwidth) = 2^k, where lambda is the Carmichael + /// function. This means that x^(2^k) === 1 mod 2^Bitwidth for + /// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic. + /// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every + /// even x in Bitwidth-bit arithmetic. + static unsigned CarmichaelShift(unsigned Bitwidth) { + if (Bitwidth < 3) + return Bitwidth - 1; + return Bitwidth - 2; + } + + /// Add the extra weight 'RHS' to the existing weight 'LHS', + /// reducing the combined weight using any special properties of the operation. + /// The existing weight LHS represents the computation X op X op ... op X where + /// X occurs LHS times. The combined weight represents X op X op ... op X with + /// X occurring LHS + RHS times. If op is "Xor" for example then the combined + /// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even; + /// the routine returns 1 in LHS in the first case, and 0 in LHS in the second. + static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) { + // If we were working with infinite precision arithmetic then the combined + // weight would be LHS + RHS. But we are using finite precision arithmetic, + // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct + // for nilpotent operations and addition, but not for idempotent operations + // and multiplication), so it is important to correctly reduce the combined + // weight back into range if wrapping would be wrong. + + // If RHS is zero then the weight didn't change. + if (RHS.isMinValue()) + return; + // If LHS is zero then the combined weight is RHS. + if (LHS.isMinValue()) { + LHS = RHS; + return; + } + // From this point on we know that neither LHS nor RHS is zero. + + if (Instruction::isIdempotent(Opcode)) { + // Idempotent means X op X === X, so any non-zero weight is equivalent to a + // weight of 1. Keeping weights at zero or one also means that wrapping is + // not a problem. + assert(LHS == 1 && RHS == 1 && "Weights not reduced!"); + return; // Return a weight of 1. + } + if (Instruction::isNilpotent(Opcode)) { + // Nilpotent means X op X === 0, so reduce weights modulo 2. + assert(LHS == 1 && RHS == 1 && "Weights not reduced!"); + LHS = 0; // 1 + 1 === 0 modulo 2. + return; + } + if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) { + // TODO: Reduce the weight by exploiting nsw/nuw? + LHS += RHS; + return; + } + + assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) && + "Unknown associative operation!"); + unsigned Bitwidth = LHS.getBitWidth(); + // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth + // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth + // bit number x, since either x is odd in which case x^CM = 1, or x is even in + // which case both x^W and x^(W - CM) are zero. By subtracting off multiples + // of CM like this weights can always be reduced to the range [0, CM+Bitwidth) + // which by a happy accident means that they can always be represented using + // Bitwidth bits. + // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than + // the Carmichael number). + if (Bitwidth > 3) { + /// CM - The value of Carmichael's lambda function. + APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth)); + // Any weight W >= Threshold can be replaced with W - CM. + APInt Threshold = CM + Bitwidth; + assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!"); + // For Bitwidth 4 or more the following sum does not overflow. + LHS += RHS; + while (LHS.uge(Threshold)) + LHS -= CM; + } else { + // To avoid problems with overflow do everything the same as above but using + // a larger type. + unsigned CM = 1U << CarmichaelShift(Bitwidth); + unsigned Threshold = CM + Bitwidth; + assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold && + "Weights not reduced!"); + unsigned Total = LHS.getZExtValue() + RHS.getZExtValue(); + while (Total >= Threshold) + Total -= CM; + LHS = Total; + } + } + + using RepeatedValue = std::pair; + + /// Given an associative binary expression, return the leaf + /// nodes in Ops along with their weights (how many times the leaf occurs). The + /// original expression is the same as + /// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times + /// op + /// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times + /// op + /// ... + /// op + /// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times + /// + /// Note that the values Ops[0].first, ..., Ops[N].first are all distinct. + /// + /// This routine may modify the function, in which case it returns 'true'. The + /// changes it makes may well be destructive, changing the value computed by 'I' + /// to something completely different. Thus if the routine returns 'true' then + /// you MUST either replace I with a new expression computed from the Ops array, + /// or use RewriteExprTree to put the values back in. + /// + /// A leaf node is either not a binary operation of the same kind as the root + /// node 'I' (i.e. is not a binary operator at all, or is, but with a different + /// opcode), or is the same kind of binary operator but has a use which either + /// does not belong to the expression, or does belong to the expression but is + /// a leaf node. Every leaf node has at least one use that is a non-leaf node + /// of the expression, while for non-leaf nodes (except for the root 'I') every + /// use is a non-leaf node of the expression. + /// + /// For example: + /// expression graph node names + /// + /// + | I + /// / \ | + /// + + | A, B + /// / \ / \ | + /// * + * | C, D, E + /// / \ / \ / \ | + /// + * | F, G + /// + /// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in + /// that order) (C, 1), (E, 1), (F, 2), (G, 2). + /// + /// The expression is maximal: if some instruction is a binary operator of the + /// same kind as 'I', and all of its uses are non-leaf nodes of the expression, + /// then the instruction also belongs to the expression, is not a leaf node of + /// it, and its operands also belong to the expression (but may be leaf nodes). + /// + /// NOTE: This routine will set operands of non-leaf non-root nodes to undef in + /// order to ensure that every non-root node in the expression has *exactly one* + /// use by a non-leaf node of the expression. This destruction means that the + /// caller MUST either replace 'I' with a new expression or use something like + /// RewriteExprTree to put the values back in if the routine indicates that it + /// made a change by returning 'true'. + /// + /// In the above example either the right operand of A or the left operand of B + /// will be replaced by undef. If it is B's operand then this gives: + /// + /// + | I + /// / \ | + /// + + | A, B - operand of B replaced with undef + /// / \ \ | + /// * + * | C, D, E + /// / \ / \ / \ | + /// + * | F, G + /// + /// Note that such undef operands can only be reached by passing through 'I'. + /// For example, if you visit operands recursively starting from a leaf node + /// then you will never see such an undef operand unless you get back to 'I', + /// which requires passing through a phi node. + /// + /// Note that this routine may also mutate binary operators of the wrong type + /// that have all uses inside the expression (i.e. only used by non-leaf nodes + /// of the expression) if it can turn them into binary operators of the right + /// type and thus make the expression bigger. + static bool LinearizeExprTree(Instruction *I, + SmallVectorImpl &Ops) { + assert((isa(I) || isa(I)) && + "Expected a UnaryOperator or BinaryOperator!"); + LLVM_DEBUG(dbgs() << "LINEARIZE: " << *I << '\n'); + unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits(); + unsigned Opcode = I->getOpcode(); + assert(I->isAssociative() && I->isCommutative() && + "Expected an associative and commutative operation!"); + + // Visit all operands of the expression, keeping track of their weight (the + // number of paths from the expression root to the operand, or if you like + // the number of times that operand occurs in the linearized expression). + // For example, if I = X + A, where X = A + B, then I, X and B have weight 1 + // while A has weight two. + + // Worklist of non-leaf nodes (their operands are in the expression too) along + // with their weights, representing a certain number of paths to the operator. + // If an operator occurs in the worklist multiple times then we found multiple + // ways to get to it. + SmallVector, 8> Worklist; // (Op, Weight) + Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1))); + bool Changed = false; + + // Leaves of the expression are values that either aren't the right kind of + // operation (eg: a constant, or a multiply in an add tree), or are, but have + // some uses that are not inside the expression. For example, in I = X + X, + // X = A + B, the value X has two uses (by I) that are in the expression. If + // X has any other uses, for example in a return instruction, then we consider + // X to be a leaf, and won't analyze it further. When we first visit a value, + // if it has more than one use then at first we conservatively consider it to + // be a leaf. Later, as the expression is explored, we may discover some more + // uses of the value from inside the expression. If all uses turn out to be + // from within the expression (and the value is a binary operator of the right + // kind) then the value is no longer considered to be a leaf, and its operands + // are explored. + + // Leaves - Keeps track of the set of putative leaves as well as the number of + // paths to each leaf seen so far. + using LeafMap = DenseMap; + LeafMap Leaves; // Leaf -> Total weight so far. + SmallVector LeafOrder; // Ensure deterministic leaf output order. + + #ifndef NDEBUG + SmallPtrSet Visited; // For sanity checking the iteration scheme. + #endif + while (!Worklist.empty()) { + std::pair P = Worklist.pop_back_val(); + I = P.first; // We examine the operands of this binary operator. + + for (unsigned OpIdx = 0; OpIdx < I->getNumOperands(); ++OpIdx) { // Visit operands. + Value *Op = I->getOperand(OpIdx); + APInt Weight = P.second; // Number of paths to this operand. + LLVM_DEBUG(dbgs() << "OPERAND: " << *Op << " (" << Weight << ")\n"); + assert(!Op->use_empty() && "No uses, so how did we get to it?!"); + + // If this is a binary operation of the right kind with only one use then + // add its operands to the expression. + if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) { + assert(Visited.insert(Op).second && "Not first visit!"); + LLVM_DEBUG(dbgs() << "DIRECT ADD: " << *Op << " (" << Weight << ")\n"); + Worklist.push_back(std::make_pair(BO, Weight)); + continue; + } + + // Appears to be a leaf. Is the operand already in the set of leaves? + LeafMap::iterator It = Leaves.find(Op); + if (It == Leaves.end()) { + // Not in the leaf map. Must be the first time we saw this operand. + assert(Visited.insert(Op).second && "Not first visit!"); + if (!Op->hasOneUse()) { + // This value has uses not accounted for by the expression, so it is + // not safe to modify. Mark it as being a leaf. + LLVM_DEBUG(dbgs() + << "ADD USES LEAF: " << *Op << " (" << Weight << ")\n"); + LeafOrder.push_back(Op); + Leaves[Op] = Weight; + continue; + } + // No uses outside the expression, try morphing it. + } else { + // Already in the leaf map. + assert(It != Leaves.end() && Visited.count(Op) && + "In leaf map but not visited!"); + + // Update the number of paths to the leaf. + IncorporateWeight(It->second, Weight, Opcode); + + #if 0 // TODO: Re-enable once PR13021 is fixed. + // The leaf already has one use from inside the expression. As we want + // exactly one such use, drop this new use of the leaf. + assert(!Op->hasOneUse() && "Only one use, but we got here twice!"); + I->setOperand(OpIdx, UndefValue::get(I->getType())); + Changed = true; + + // If the leaf is a binary operation of the right kind and we now see + // that its multiple original uses were in fact all by nodes belonging + // to the expression, then no longer consider it to be a leaf and add + // its operands to the expression. + if (BinaryOperator *BO = isReassociableOp(Op, Opcode)) { + LLVM_DEBUG(dbgs() << "UNLEAF: " << *Op << " (" << It->second << ")\n"); + Worklist.push_back(std::make_pair(BO, It->second)); + Leaves.erase(It); + continue; + } + #endif + + // If we still have uses that are not accounted for by the expression + // then it is not safe to modify the value. + if (!Op->hasOneUse()) + continue; + + // No uses outside the expression, try morphing it. + Weight = It->second; + Leaves.erase(It); // Since the value may be morphed below. + } + + // At this point we have a value which, first of all, is not a binary + // expression of the right kind, and secondly, is only used inside the + // expression. This means that it can safely be modified. See if we + // can usefully morph it into an expression of the right kind. + assert((!isa(Op) || + cast(Op)->getOpcode() != Opcode + || (isa(Op) && + !cast(Op)->isFast())) && + "Should have been handled above!"); + assert(Op->hasOneUse() && "Has uses outside the expression tree!"); + + // If this is a multiply expression, turn any internal negations into + // multiplies by -1 so they can be reassociated. + if (Instruction *Tmp = dyn_cast(Op)) + if ((Opcode == Instruction::Mul && match(Tmp, m_Neg(m_Value()))) || + (Opcode == Instruction::FMul && match(Tmp, m_FNeg(m_Value())))) { + LLVM_DEBUG(dbgs() + << "MORPH LEAF: " << *Op << " (" << Weight << ") TO "); + Tmp = LowerNegateToMultiply(Tmp); + LLVM_DEBUG(dbgs() << *Tmp << '\n'); + Worklist.push_back(std::make_pair(Tmp, Weight)); + Changed = true; + continue; + } + + // Failed to morph into an expression of the right type. This really is + // a leaf. + LLVM_DEBUG(dbgs() << "ADD LEAF: " << *Op << " (" << Weight << ")\n"); + assert(!isReassociableOp(Op, Opcode) && "Value was morphed?"); + LeafOrder.push_back(Op); + Leaves[Op] = Weight; + } + } + + // The leaves, repeated according to their weights, represent the linearized + // form of the expression. + for (unsigned i = 0, e = LeafOrder.size(); i != e; ++i) { + Value *V = LeafOrder[i]; + LeafMap::iterator It = Leaves.find(V); + if (It == Leaves.end()) + // Node initially thought to be a leaf wasn't. + continue; + assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!"); + APInt Weight = It->second; + if (Weight.isMinValue()) + // Leaf already output or weight reduction eliminated it. + continue; + // Ensure the leaf is only output once. + It->second = 0; + Ops.push_back(std::make_pair(V, Weight)); + } + + // For nilpotent operations or addition there may be no operands, for example + // because the expression was "X xor X" or consisted of 2^Bitwidth additions: + // in both cases the weight reduces to 0 causing the value to be skipped. + if (Ops.empty()) { + Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType()); + assert(Identity && "Associative operation without identity!"); + Ops.emplace_back(Identity, APInt(Bitwidth, 1)); + } + + return Changed; + } + + /// Now that the operands for this expression tree are + /// linearized and optimized, emit them in-order. + void ReassociatePass::RewriteExprTree(BinaryOperator *I, + SmallVectorImpl &Ops) { + assert(Ops.size() > 1 && "Single values should be used directly!"); + + // Since our optimizations should never increase the number of operations, the + // new expression can usually be written reusing the existing binary operators + // from the original expression tree, without creating any new instructions, + // though the rewritten expression may have a completely different topology. + // We take care to not change anything if the new expression will be the same + // as the original. If more than trivial changes (like commuting operands) + // were made then we are obliged to clear out any optional subclass data like + // nsw flags. + + /// NodesToRewrite - Nodes from the original expression available for writing + /// the new expression into. + SmallVector NodesToRewrite; + unsigned Opcode = I->getOpcode(); + BinaryOperator *Op = I; + + /// NotRewritable - The operands being written will be the leaves of the new + /// expression and must not be used as inner nodes (via NodesToRewrite) by + /// mistake. Inner nodes are always reassociable, and usually leaves are not + /// (if they were they would have been incorporated into the expression and so + /// would not be leaves), so most of the time there is no danger of this. But + /// in rare cases a leaf may become reassociable if an optimization kills uses + /// of it, or it may momentarily become reassociable during rewriting (below) + /// due it being removed as an operand of one of its uses. Ensure that misuse + /// of leaf nodes as inner nodes cannot occur by remembering all of the future + /// leaves and refusing to reuse any of them as inner nodes. + SmallPtrSet NotRewritable; + for (unsigned i = 0, e = Ops.size(); i != e; ++i) + NotRewritable.insert(Ops[i].Op); + + // ExpressionChanged - Non-null if the rewritten expression differs from the + // original in some non-trivial way, requiring the clearing of optional flags. + // Flags are cleared from the operator in ExpressionChanged up to I inclusive. + BinaryOperator *ExpressionChanged = nullptr; + for (unsigned i = 0; ; ++i) { + // The last operation (which comes earliest in the IR) is special as both + // operands will come from Ops, rather than just one with the other being + // a subexpression. + if (i+2 == Ops.size()) { + Value *NewLHS = Ops[i].Op; + Value *NewRHS = Ops[i+1].Op; + Value *OldLHS = Op->getOperand(0); + Value *OldRHS = Op->getOperand(1); + + if (NewLHS == OldLHS && NewRHS == OldRHS) + // Nothing changed, leave it alone. + break; + + if (NewLHS == OldRHS && NewRHS == OldLHS) { + // The order of the operands was reversed. Swap them. + LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n'); + Op->swapOperands(); + LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n'); + MadeChange = true; + ++NumChanged; + break; + } + + // The new operation differs non-trivially from the original. Overwrite + // the old operands with the new ones. + LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n'); + if (NewLHS != OldLHS) { + BinaryOperator *BO = isReassociableOp(OldLHS, Opcode); + if (BO && !NotRewritable.count(BO)) + NodesToRewrite.push_back(BO); + Op->setOperand(0, NewLHS); + } + if (NewRHS != OldRHS) { + BinaryOperator *BO = isReassociableOp(OldRHS, Opcode); + if (BO && !NotRewritable.count(BO)) + NodesToRewrite.push_back(BO); + Op->setOperand(1, NewRHS); + } + LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n'); + + ExpressionChanged = Op; + MadeChange = true; + ++NumChanged; + + break; + } + + // Not the last operation. The left-hand side will be a sub-expression + // while the right-hand side will be the current element of Ops. + Value *NewRHS = Ops[i].Op; + if (NewRHS != Op->getOperand(1)) { + LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n'); + if (NewRHS == Op->getOperand(0)) { + // The new right-hand side was already present as the left operand. If + // we are lucky then swapping the operands will sort out both of them. + Op->swapOperands(); + } else { + // Overwrite with the new right-hand side. + BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode); + if (BO && !NotRewritable.count(BO)) + NodesToRewrite.push_back(BO); + Op->setOperand(1, NewRHS); + ExpressionChanged = Op; + } + LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n'); + MadeChange = true; + ++NumChanged; + } + + // Now deal with the left-hand side. If this is already an operation node + // from the original expression then just rewrite the rest of the expression + // into it. + BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode); + if (BO && !NotRewritable.count(BO)) { + Op = BO; + continue; + } + + // Otherwise, grab a spare node from the original expression and use that as + // the left-hand side. If there are no nodes left then the optimizers made + // an expression with more nodes than the original! This usually means that + // they did something stupid but it might mean that the problem was just too + // hard (finding the mimimal number of multiplications needed to realize a + // multiplication expression is NP-complete). Whatever the reason, smart or + // stupid, create a new node if there are none left. + BinaryOperator *NewOp; + if (NodesToRewrite.empty()) { + Constant *Undef = UndefValue::get(I->getType()); + NewOp = BinaryOperator::Create(Instruction::BinaryOps(Opcode), + Undef, Undef, "", I); + if (NewOp->getType()->isFPOrFPVectorTy()) + NewOp->setFastMathFlags(I->getFastMathFlags()); + } else { + NewOp = NodesToRewrite.pop_back_val(); + } + + LLVM_DEBUG(dbgs() << "RA: " << *Op << '\n'); + Op->setOperand(0, NewOp); + LLVM_DEBUG(dbgs() << "TO: " << *Op << '\n'); + ExpressionChanged = Op; + MadeChange = true; + ++NumChanged; + Op = NewOp; + } + + // If the expression changed non-trivially then clear out all subclass data + // starting from the operator specified in ExpressionChanged, and compactify + // the operators to just before the expression root to guarantee that the + // expression tree is dominated by all of Ops. + if (ExpressionChanged) + do { + // Preserve FastMathFlags. + if (isa(I)) { + FastMathFlags Flags = I->getFastMathFlags(); + ExpressionChanged->clearSubclassOptionalData(); + ExpressionChanged->setFastMathFlags(Flags); + } else + ExpressionChanged->clearSubclassOptionalData(); + + if (ExpressionChanged == I) + break; + + // Discard any debug info related to the expressions that has changed (we + // can leave debug infor related to the root, since the result of the + // expression tree should be the same even after reassociation). + replaceDbgUsesWithUndef(ExpressionChanged); + + ExpressionChanged->moveBefore(I); + ExpressionChanged = cast(*ExpressionChanged->user_begin()); + } while (true); + + // Throw away any left over nodes from the original expression. + for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i) + RedoInsts.insert(NodesToRewrite[i]); + } + + /// Insert instructions before the instruction pointed to by BI, + /// that computes the negative version of the value specified. The negative + /// version of the value is returned, and BI is left pointing at the instruction + /// that should be processed next by the reassociation pass. + /// Also add intermediate instructions to the redo list that are modified while + /// pushing the negates through adds. These will be revisited to see if + /// additional opportunities have been exposed. + static Value *NegateValue(Value *V, Instruction *BI, + ReassociatePass::OrderedSet &ToRedo) { + if (auto *C = dyn_cast(V)) + return C->getType()->isFPOrFPVectorTy() ? ConstantExpr::getFNeg(C) : + ConstantExpr::getNeg(C); + + // We are trying to expose opportunity for reassociation. One of the things + // that we want to do to achieve this is to push a negation as deep into an + // expression chain as possible, to expose the add instructions. In practice, + // this means that we turn this: + // X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D + // so that later, a: Y = 12+X could get reassociated with the -12 to eliminate + // the constants. We assume that instcombine will clean up the mess later if + // we introduce tons of unnecessary negation instructions. + // + if (BinaryOperator *I = + isReassociableOp(V, Instruction::Add, Instruction::FAdd)) { + // Push the negates through the add. + I->setOperand(0, NegateValue(I->getOperand(0), BI, ToRedo)); + I->setOperand(1, NegateValue(I->getOperand(1), BI, ToRedo)); + if (I->getOpcode() == Instruction::Add) { + I->setHasNoUnsignedWrap(false); + I->setHasNoSignedWrap(false); + } + + // We must move the add instruction here, because the neg instructions do + // not dominate the old add instruction in general. By moving it, we are + // assured that the neg instructions we just inserted dominate the + // instruction we are about to insert after them. + // + I->moveBefore(BI); + I->setName(I->getName()+".neg"); + + // Add the intermediate negates to the redo list as processing them later + // could expose more reassociating opportunities. + ToRedo.insert(I); + return I; + } + + // Okay, we need to materialize a negated version of V with an instruction. + // Scan the use lists of V to see if we have one already. + for (User *U : V->users()) { + if (!match(U, m_Neg(m_Value())) && !match(U, m_FNeg(m_Value()))) + continue; + + // We found one! Now we have to make sure that the definition dominates + // this use. We do this by moving it to the entry block (if it is a + // non-instruction value) or right after the definition. These negates will + // be zapped by reassociate later, so we don't need much finesse here. + Instruction *TheNeg = cast(U); + + // Verify that the negate is in this function, V might be a constant expr. + if (TheNeg->getParent()->getParent() != BI->getParent()->getParent()) + continue; + + bool FoundCatchSwitch = false; + + BasicBlock::iterator InsertPt; + if (Instruction *InstInput = dyn_cast(V)) { + if (InvokeInst *II = dyn_cast(InstInput)) { + InsertPt = II->getNormalDest()->begin(); + } else { + InsertPt = ++InstInput->getIterator(); + } + + const BasicBlock *BB = InsertPt->getParent(); + + // Make sure we don't move anything before PHIs or exception + // handling pads. + while (InsertPt != BB->end() && (isa(InsertPt) || + InsertPt->isEHPad())) { + if (isa(InsertPt)) + // A catchswitch cannot have anything in the block except + // itself and PHIs. We'll bail out below. + FoundCatchSwitch = true; + ++InsertPt; + } + } else { + InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin(); + } + + // We found a catchswitch in the block where we want to move the + // neg. We cannot move anything into that block. Bail and just + // create the neg before BI, as if we hadn't found an existing + // neg. + if (FoundCatchSwitch) + break; + + TheNeg->moveBefore(&*InsertPt); + if (TheNeg->getOpcode() == Instruction::Sub) { + TheNeg->setHasNoUnsignedWrap(false); + TheNeg->setHasNoSignedWrap(false); + } else { + TheNeg->andIRFlags(BI); + } + ToRedo.insert(TheNeg); + return TheNeg; + } + + // Insert a 'neg' instruction that subtracts the value from zero to get the + // negation. + BinaryOperator *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI); + ToRedo.insert(NewNeg); + return NewNeg; + } + + /// Return true if we should break up this subtract of X-Y into (X + -Y). + static bool ShouldBreakUpSubtract(Instruction *Sub) { + // If this is a negation, we can't split it up! + if (match(Sub, m_Neg(m_Value())) || match(Sub, m_FNeg(m_Value()))) + return false; + + // Don't breakup X - undef. + if (isa(Sub->getOperand(1))) + return false; + + // Don't bother to break this up unless either the LHS is an associable add or + // subtract or if this is only used by one. + Value *V0 = Sub->getOperand(0); + if (isReassociableOp(V0, Instruction::Add, Instruction::FAdd) || + isReassociableOp(V0, Instruction::Sub, Instruction::FSub)) + return true; + Value *V1 = Sub->getOperand(1); + if (isReassociableOp(V1, Instruction::Add, Instruction::FAdd) || + isReassociableOp(V1, Instruction::Sub, Instruction::FSub)) + return true; + Value *VB = Sub->user_back(); + if (Sub->hasOneUse() && + (isReassociableOp(VB, Instruction::Add, Instruction::FAdd) || + isReassociableOp(VB, Instruction::Sub, Instruction::FSub))) + return true; + + return false; + } + + /// If we have (X-Y), and if either X is an add, or if this is only used by an + /// add, transform this into (X+(0-Y)) to promote better reassociation. + static BinaryOperator *BreakUpSubtract(Instruction *Sub, + ReassociatePass::OrderedSet &ToRedo) { + // Convert a subtract into an add and a neg instruction. This allows sub + // instructions to be commuted with other add instructions. + // + // Calculate the negative value of Operand 1 of the sub instruction, + // and set it as the RHS of the add instruction we just made. + Value *NegVal = NegateValue(Sub->getOperand(1), Sub, ToRedo); + BinaryOperator *New = CreateAdd(Sub->getOperand(0), NegVal, "", Sub, Sub); + Sub->setOperand(0, Constant::getNullValue(Sub->getType())); // Drop use of op. + Sub->setOperand(1, Constant::getNullValue(Sub->getType())); // Drop use of op. + New->takeName(Sub); + + // Everyone now refers to the add instruction. + Sub->replaceAllUsesWith(New); + New->setDebugLoc(Sub->getDebugLoc()); + + LLVM_DEBUG(dbgs() << "Negated: " << *New << '\n'); + return New; + } + + /// If this is a shift of a reassociable multiply or is used by one, change + /// this into a multiply by a constant to assist with further reassociation. + static BinaryOperator *ConvertShiftToMul(Instruction *Shl) { + Constant *MulCst = ConstantInt::get(Shl->getType(), 1); + MulCst = ConstantExpr::getShl(MulCst, cast(Shl->getOperand(1))); + + BinaryOperator *Mul = + BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl); + Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op. + Mul->takeName(Shl); + + // Everyone now refers to the mul instruction. + Shl->replaceAllUsesWith(Mul); + Mul->setDebugLoc(Shl->getDebugLoc()); + + // We can safely preserve the nuw flag in all cases. It's also safe to turn a + // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special + // handling. + bool NSW = cast(Shl)->hasNoSignedWrap(); + bool NUW = cast(Shl)->hasNoUnsignedWrap(); + if (NSW && NUW) + Mul->setHasNoSignedWrap(true); + Mul->setHasNoUnsignedWrap(NUW); + return Mul; + } + + /// Scan backwards and forwards among values with the same rank as element i + /// to see if X exists. If X does not exist, return i. This is useful when + /// scanning for 'x' when we see '-x' because they both get the same rank. + static unsigned FindInOperandList(const SmallVectorImpl &Ops, + unsigned i, Value *X) { + unsigned XRank = Ops[i].Rank; + unsigned e = Ops.size(); + for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) { + if (Ops[j].Op == X) + return j; + if (Instruction *I1 = dyn_cast(Ops[j].Op)) + if (Instruction *I2 = dyn_cast(X)) + if (I1->isIdenticalTo(I2)) + return j; + } + // Scan backwards. + for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) { + if (Ops[j].Op == X) + return j; + if (Instruction *I1 = dyn_cast(Ops[j].Op)) + if (Instruction *I2 = dyn_cast(X)) + if (I1->isIdenticalTo(I2)) + return j; + } + return i; + } + + /// Emit a tree of add instructions, summing Ops together + /// and returning the result. Insert the tree before I. + static Value *EmitAddTreeOfValues(Instruction *I, + SmallVectorImpl &Ops) { + if (Ops.size() == 1) return Ops.back(); + + Value *V1 = Ops.back(); + Ops.pop_back(); + Value *V2 = EmitAddTreeOfValues(I, Ops); + return CreateAdd(V2, V1, "reass.add", I, I); + } + + /// If V is an expression tree that is a multiplication sequence, + /// and if this sequence contains a multiply by Factor, + /// remove Factor from the tree and return the new tree. + Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor) { + BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul); + if (!BO) + return nullptr; + + SmallVector Tree; + MadeChange |= LinearizeExprTree(BO, Tree); + SmallVector Factors; + Factors.reserve(Tree.size()); + for (unsigned i = 0, e = Tree.size(); i != e; ++i) { + RepeatedValue E = Tree[i]; + Factors.append(E.second.getZExtValue(), + ValueEntry(getRank(E.first), E.first)); + } + + bool FoundFactor = false; + bool NeedsNegate = false; + for (unsigned i = 0, e = Factors.size(); i != e; ++i) { + if (Factors[i].Op == Factor) { + FoundFactor = true; + Factors.erase(Factors.begin()+i); + break; + } + + // If this is a negative version of this factor, remove it. + if (ConstantInt *FC1 = dyn_cast(Factor)) { + if (ConstantInt *FC2 = dyn_cast(Factors[i].Op)) + if (FC1->getValue() == -FC2->getValue()) { + FoundFactor = NeedsNegate = true; + Factors.erase(Factors.begin()+i); + break; + } + } else if (ConstantFP *FC1 = dyn_cast(Factor)) { + if (ConstantFP *FC2 = dyn_cast(Factors[i].Op)) { + const APFloat &F1 = FC1->getValueAPF(); + APFloat F2(FC2->getValueAPF()); + F2.changeSign(); + if (F1.compare(F2) == APFloat::cmpEqual) { + FoundFactor = NeedsNegate = true; + Factors.erase(Factors.begin() + i); + break; + } + } + } + } + + if (!FoundFactor) { + // Make sure to restore the operands to the expression tree. + RewriteExprTree(BO, Factors); + return nullptr; + } + + BasicBlock::iterator InsertPt = ++BO->getIterator(); + + // If this was just a single multiply, remove the multiply and return the only + // remaining operand. + if (Factors.size() == 1) { + RedoInsts.insert(BO); + V = Factors[0].Op; + } else { + RewriteExprTree(BO, Factors); + V = BO; + } + + if (NeedsNegate) + V = CreateNeg(V, "neg", &*InsertPt, BO); + + return V; + } + + /// If V is a single-use multiply, recursively add its operands as factors, + /// otherwise add V to the list of factors. + /// + /// Ops is the top-level list of add operands we're trying to factor. + static void FindSingleUseMultiplyFactors(Value *V, + SmallVectorImpl &Factors) { + BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul); + if (!BO) { + Factors.push_back(V); + return; + } + + // Otherwise, add the LHS and RHS to the list of factors. + FindSingleUseMultiplyFactors(BO->getOperand(1), Factors); + FindSingleUseMultiplyFactors(BO->getOperand(0), Factors); + } + + /// Optimize a series of operands to an 'and', 'or', or 'xor' instruction. + /// This optimizes based on identities. If it can be reduced to a single Value, + /// it is returned, otherwise the Ops list is mutated as necessary. + static Value *OptimizeAndOrXor(unsigned Opcode, + SmallVectorImpl &Ops) { + // Scan the operand lists looking for X and ~X pairs, along with X,X pairs. + // If we find any, we can simplify the expression. X&~X == 0, X|~X == -1. + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + // First, check for X and ~X in the operand list. + assert(i < Ops.size()); + Value *X; + if (match(Ops[i].Op, m_Not(m_Value(X)))) { // Cannot occur for ^. + unsigned FoundX = FindInOperandList(Ops, i, X); + if (FoundX != i) { + if (Opcode == Instruction::And) // ...&X&~X = 0 + return Constant::getNullValue(X->getType()); + + if (Opcode == Instruction::Or) // ...|X|~X = -1 + return Constant::getAllOnesValue(X->getType()); + } + } + + // Next, check for duplicate pairs of values, which we assume are next to + // each other, due to our sorting criteria. + assert(i < Ops.size()); + if (i+1 != Ops.size() && Ops[i+1].Op == Ops[i].Op) { + if (Opcode == Instruction::And || Opcode == Instruction::Or) { + // Drop duplicate values for And and Or. + Ops.erase(Ops.begin()+i); + --i; --e; + ++NumAnnihil; + continue; + } + + // Drop pairs of values for Xor. + assert(Opcode == Instruction::Xor); + if (e == 2) + return Constant::getNullValue(Ops[0].Op->getType()); + + // Y ^ X^X -> Y + Ops.erase(Ops.begin()+i, Ops.begin()+i+2); + i -= 1; e -= 2; + ++NumAnnihil; + } + } + return nullptr; + } + + /// Helper function of CombineXorOpnd(). It creates a bitwise-and + /// instruction with the given two operands, and return the resulting + /// instruction. There are two special cases: 1) if the constant operand is 0, + /// it will return NULL. 2) if the constant is ~0, the symbolic operand will + /// be returned. + static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd, + const APInt &ConstOpnd) { + if (ConstOpnd.isNullValue()) + return nullptr; + + if (ConstOpnd.isAllOnesValue()) + return Opnd; + + Instruction *I = BinaryOperator::CreateAnd( + Opnd, ConstantInt::get(Opnd->getType(), ConstOpnd), "and.ra", + InsertBefore); + I->setDebugLoc(InsertBefore->getDebugLoc()); + return I; + } + + // Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd" + // into "R ^ C", where C would be 0, and R is a symbolic value. + // + // If it was successful, true is returned, and the "R" and "C" is returned + // via "Res" and "ConstOpnd", respectively; otherwise, false is returned, + // and both "Res" and "ConstOpnd" remain unchanged. + bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, + APInt &ConstOpnd, Value *&Res) { + // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2 + // = ((x | c1) ^ c1) ^ (c1 ^ c2) + // = (x & ~c1) ^ (c1 ^ c2) + // It is useful only when c1 == c2. + if (!Opnd1->isOrExpr() || Opnd1->getConstPart().isNullValue()) + return false; + + if (!Opnd1->getValue()->hasOneUse()) + return false; + + const APInt &C1 = Opnd1->getConstPart(); + if (C1 != ConstOpnd) + return false; + + Value *X = Opnd1->getSymbolicPart(); + Res = createAndInstr(I, X, ~C1); + // ConstOpnd was C2, now C1 ^ C2. + ConstOpnd ^= C1; + + if (Instruction *T = dyn_cast(Opnd1->getValue())) + RedoInsts.insert(T); + return true; + } + + // Helper function of OptimizeXor(). It tries to simplify + // "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a + // symbolic value. + // + // If it was successful, true is returned, and the "R" and "C" is returned + // via "Res" and "ConstOpnd", respectively (If the entire expression is + // evaluated to a constant, the Res is set to NULL); otherwise, false is + // returned, and both "Res" and "ConstOpnd" remain unchanged. + bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, + XorOpnd *Opnd2, APInt &ConstOpnd, + Value *&Res) { + Value *X = Opnd1->getSymbolicPart(); + if (X != Opnd2->getSymbolicPart()) + return false; + + // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.) + int DeadInstNum = 1; + if (Opnd1->getValue()->hasOneUse()) + DeadInstNum++; + if (Opnd2->getValue()->hasOneUse()) + DeadInstNum++; + + // Xor-Rule 2: + // (x | c1) ^ (x & c2) + // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1 + // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1 + // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3 + // + if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) { + if (Opnd2->isOrExpr()) + std::swap(Opnd1, Opnd2); + + const APInt &C1 = Opnd1->getConstPart(); + const APInt &C2 = Opnd2->getConstPart(); + APInt C3((~C1) ^ C2); + + // Do not increase code size! + if (!C3.isNullValue() && !C3.isAllOnesValue()) { + int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2; + if (NewInstNum > DeadInstNum) + return false; + } + + Res = createAndInstr(I, X, C3); + ConstOpnd ^= C1; + } else if (Opnd1->isOrExpr()) { + // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2 + // + const APInt &C1 = Opnd1->getConstPart(); + const APInt &C2 = Opnd2->getConstPart(); + APInt C3 = C1 ^ C2; + + // Do not increase code size + if (!C3.isNullValue() && !C3.isAllOnesValue()) { + int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2; + if (NewInstNum > DeadInstNum) + return false; + } + + Res = createAndInstr(I, X, C3); + ConstOpnd ^= C3; + } else { + // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2)) + // + const APInt &C1 = Opnd1->getConstPart(); + const APInt &C2 = Opnd2->getConstPart(); + APInt C3 = C1 ^ C2; + Res = createAndInstr(I, X, C3); + } + + // Put the original operands in the Redo list; hope they will be deleted + // as dead code. + if (Instruction *T = dyn_cast(Opnd1->getValue())) + RedoInsts.insert(T); + if (Instruction *T = dyn_cast(Opnd2->getValue())) + RedoInsts.insert(T); + + return true; + } + + /// Optimize a series of operands to an 'xor' instruction. If it can be reduced + /// to a single Value, it is returned, otherwise the Ops list is mutated as + /// necessary. + Value *ReassociatePass::OptimizeXor(Instruction *I, + SmallVectorImpl &Ops) { + if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops)) + return V; + + if (Ops.size() == 1) + return nullptr; + + SmallVector Opnds; + SmallVector OpndPtrs; + Type *Ty = Ops[0].Op->getType(); + APInt ConstOpnd(Ty->getScalarSizeInBits(), 0); + + // Step 1: Convert ValueEntry to XorOpnd + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + Value *V = Ops[i].Op; + const APInt *C; + // TODO: Support non-splat vectors. + if (match(V, m_APInt(C))) { + ConstOpnd ^= *C; + } else { + XorOpnd O(V); + O.setSymbolicRank(getRank(O.getSymbolicPart())); + Opnds.push_back(O); + } + } + + // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds". + // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate + // the "OpndPtrs" as well. For the similar reason, do not fuse this loop + // with the previous loop --- the iterator of the "Opnds" may be invalidated + // when new elements are added to the vector. + for (unsigned i = 0, e = Opnds.size(); i != e; ++i) + OpndPtrs.push_back(&Opnds[i]); + + // Step 2: Sort the Xor-Operands in a way such that the operands containing + // the same symbolic value cluster together. For instance, the input operand + // sequence ("x | 123", "y & 456", "x & 789") will be sorted into: + // ("x | 123", "x & 789", "y & 456"). + // + // The purpose is twofold: + // 1) Cluster together the operands sharing the same symbolic-value. + // 2) Operand having smaller symbolic-value-rank is permuted earlier, which + // could potentially shorten crital path, and expose more loop-invariants. + // Note that values' rank are basically defined in RPO order (FIXME). + // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier + // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2", + // "z" in the order of X-Y-Z is better than any other orders. + llvm::stable_sort(OpndPtrs, [](XorOpnd *LHS, XorOpnd *RHS) { + return LHS->getSymbolicRank() < RHS->getSymbolicRank(); + }); + + // Step 3: Combine adjacent operands + XorOpnd *PrevOpnd = nullptr; + bool Changed = false; + for (unsigned i = 0, e = Opnds.size(); i < e; i++) { + XorOpnd *CurrOpnd = OpndPtrs[i]; + // The combined value + Value *CV; + + // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd" + if (!ConstOpnd.isNullValue() && + CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) { + Changed = true; + if (CV) + *CurrOpnd = XorOpnd(CV); + else { + CurrOpnd->Invalidate(); + continue; + } + } + + if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) { + PrevOpnd = CurrOpnd; + continue; + } + + // step 3.2: When previous and current operands share the same symbolic + // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd" + if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) { + // Remove previous operand + PrevOpnd->Invalidate(); + if (CV) { + *CurrOpnd = XorOpnd(CV); + PrevOpnd = CurrOpnd; + } else { + CurrOpnd->Invalidate(); + PrevOpnd = nullptr; + } + Changed = true; + } + } + + // Step 4: Reassemble the Ops + if (Changed) { + Ops.clear(); + for (unsigned int i = 0, e = Opnds.size(); i < e; i++) { + XorOpnd &O = Opnds[i]; + if (O.isInvalid()) + continue; + ValueEntry VE(getRank(O.getValue()), O.getValue()); + Ops.push_back(VE); + } + if (!ConstOpnd.isNullValue()) { + Value *C = ConstantInt::get(Ty, ConstOpnd); + ValueEntry VE(getRank(C), C); + Ops.push_back(VE); + } + unsigned Sz = Ops.size(); + if (Sz == 1) + return Ops.back().Op; + if (Sz == 0) { + assert(ConstOpnd.isNullValue()); + return ConstantInt::get(Ty, ConstOpnd); + } + } + + return nullptr; + } + + /// Optimize a series of operands to an 'add' instruction. This + /// optimizes based on identities. If it can be reduced to a single Value, it + /// is returned, otherwise the Ops list is mutated as necessary. + Value *ReassociatePass::OptimizeAdd(Instruction *I, + SmallVectorImpl &Ops) { + // Scan the operand lists looking for X and -X pairs. If we find any, we + // can simplify expressions like X+-X == 0 and X+~X ==-1. While we're at it, + // scan for any + // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z. + + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + Value *TheOp = Ops[i].Op; + // Check to see if we've seen this operand before. If so, we factor all + // instances of the operand together. Due to our sorting criteria, we know + // that these need to be next to each other in the vector. + if (i+1 != Ops.size() && Ops[i+1].Op == TheOp) { + // Rescan the list, remove all instances of this operand from the expr. + unsigned NumFound = 0; + do { + Ops.erase(Ops.begin()+i); + ++NumFound; + } while (i != Ops.size() && Ops[i].Op == TheOp); + + LLVM_DEBUG(dbgs() << "\nFACTORING [" << NumFound << "]: " << *TheOp + << '\n'); + ++NumFactor; + + // Insert a new multiply. + Type *Ty = TheOp->getType(); + Constant *C = Ty->isIntOrIntVectorTy() ? + ConstantInt::get(Ty, NumFound) : ConstantFP::get(Ty, NumFound); + Instruction *Mul = CreateMul(TheOp, C, "factor", I, I); + + // Now that we have inserted a multiply, optimize it. This allows us to + // handle cases that require multiple factoring steps, such as this: + // (X*2) + (X*2) + (X*2) -> (X*2)*3 -> X*6 + RedoInsts.insert(Mul); + + // If every add operand was a duplicate, return the multiply. + if (Ops.empty()) + return Mul; + + // Otherwise, we had some input that didn't have the dupe, such as + // "A + A + B" -> "A*2 + B". Add the new multiply to the list of + // things being added by this operation. + Ops.insert(Ops.begin(), ValueEntry(getRank(Mul), Mul)); + + --i; + e = Ops.size(); + continue; + } + + // Check for X and -X or X and ~X in the operand list. + Value *X; + if (!match(TheOp, m_Neg(m_Value(X))) && !match(TheOp, m_Not(m_Value(X))) && + !match(TheOp, m_FNeg(m_Value(X)))) + continue; + + unsigned FoundX = FindInOperandList(Ops, i, X); + if (FoundX == i) + continue; + + // Remove X and -X from the operand list. + if (Ops.size() == 2 && + (match(TheOp, m_Neg(m_Value())) || match(TheOp, m_FNeg(m_Value())))) + return Constant::getNullValue(X->getType()); + + // Remove X and ~X from the operand list. + if (Ops.size() == 2 && match(TheOp, m_Not(m_Value()))) + return Constant::getAllOnesValue(X->getType()); + + Ops.erase(Ops.begin()+i); + if (i < FoundX) + --FoundX; + else + --i; // Need to back up an extra one. + Ops.erase(Ops.begin()+FoundX); + ++NumAnnihil; + --i; // Revisit element. + e -= 2; // Removed two elements. + + // if X and ~X we append -1 to the operand list. + if (match(TheOp, m_Not(m_Value()))) { + Value *V = Constant::getAllOnesValue(X->getType()); + Ops.insert(Ops.end(), ValueEntry(getRank(V), V)); + e += 1; + } + } + + // Scan the operand list, checking to see if there are any common factors + // between operands. Consider something like A*A+A*B*C+D. We would like to + // reassociate this to A*(A+B*C)+D, which reduces the number of multiplies. + // To efficiently find this, we count the number of times a factor occurs + // for any ADD operands that are MULs. + DenseMap FactorOccurrences; + + // Keep track of each multiply we see, to avoid triggering on (X*4)+(X*4) + // where they are actually the same multiply. + unsigned MaxOcc = 0; + Value *MaxOccVal = nullptr; + for (unsigned i = 0, e = Ops.size(); i != e; ++i) { + BinaryOperator *BOp = + isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul); + if (!BOp) + continue; + + // Compute all of the factors of this added value. + SmallVector Factors; + FindSingleUseMultiplyFactors(BOp, Factors); + assert(Factors.size() > 1 && "Bad linearize!"); + + // Add one to FactorOccurrences for each unique factor in this op. + SmallPtrSet Duplicates; + for (unsigned i = 0, e = Factors.size(); i != e; ++i) { + Value *Factor = Factors[i]; + if (!Duplicates.insert(Factor).second) + continue; + + unsigned Occ = ++FactorOccurrences[Factor]; + if (Occ > MaxOcc) { + MaxOcc = Occ; + MaxOccVal = Factor; + } + + // If Factor is a negative constant, add the negated value as a factor + // because we can percolate the negate out. Watch for minint, which + // cannot be positivified. + if (ConstantInt *CI = dyn_cast(Factor)) { + if (CI->isNegative() && !CI->isMinValue(true)) { + Factor = ConstantInt::get(CI->getContext(), -CI->getValue()); + if (!Duplicates.insert(Factor).second) + continue; + unsigned Occ = ++FactorOccurrences[Factor]; + if (Occ > MaxOcc) { + MaxOcc = Occ; + MaxOccVal = Factor; + } + } + } else if (ConstantFP *CF = dyn_cast(Factor)) { + if (CF->isNegative()) { + APFloat F(CF->getValueAPF()); + F.changeSign(); + Factor = ConstantFP::get(CF->getContext(), F); + if (!Duplicates.insert(Factor).second) + continue; + unsigned Occ = ++FactorOccurrences[Factor]; + if (Occ > MaxOcc) { + MaxOcc = Occ; + MaxOccVal = Factor; + } + } + } + } + } + + // If any factor occurred more than one time, we can pull it out. + if (MaxOcc > 1) { + LLVM_DEBUG(dbgs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal + << '\n'); + ++NumFactor; + + // Create a new instruction that uses the MaxOccVal twice. If we don't do + // this, we could otherwise run into situations where removing a factor + // from an expression will drop a use of maxocc, and this can cause + // RemoveFactorFromExpression on successive values to behave differently. + Instruction *DummyInst = + I->getType()->isIntOrIntVectorTy() + ? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal) + : BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal); + + SmallVector NewMulOps; + for (unsigned i = 0; i != Ops.size(); ++i) { + // Only try to remove factors from expressions we're allowed to. + BinaryOperator *BOp = + isReassociableOp(Ops[i].Op, Instruction::Mul, Instruction::FMul); + if (!BOp) + continue; + + if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) { + // The factorized operand may occur several times. Convert them all in + // one fell swoop. + for (unsigned j = Ops.size(); j != i;) { + --j; + if (Ops[j].Op == Ops[i].Op) { + NewMulOps.push_back(V); + Ops.erase(Ops.begin()+j); + } + } + --i; + } + } + + // No need for extra uses anymore. + DummyInst->deleteValue(); + + unsigned NumAddedValues = NewMulOps.size(); + Value *V = EmitAddTreeOfValues(I, NewMulOps); + + // Now that we have inserted the add tree, optimize it. This allows us to + // handle cases that require multiple factoring steps, such as this: + // A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C)) + assert(NumAddedValues > 1 && "Each occurrence should contribute a value"); + (void)NumAddedValues; + if (Instruction *VI = dyn_cast(V)) + RedoInsts.insert(VI); + + // Create the multiply. + Instruction *V2 = CreateMul(V, MaxOccVal, "reass.mul", I, I); + + // Rerun associate on the multiply in case the inner expression turned into + // a multiply. We want to make sure that we keep things in canonical form. + RedoInsts.insert(V2); + + // If every add operand included the factor (e.g. "A*B + A*C"), then the + // entire result expression is just the multiply "A*(B+C)". + if (Ops.empty()) + return V2; + + // Otherwise, we had some input that didn't have the factor, such as + // "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of + // things being added by this operation. + Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2)); + } + + return nullptr; + } + + /// Build up a vector of value/power pairs factoring a product. + /// + /// Given a series of multiplication operands, build a vector of factors and + /// the powers each is raised to when forming the final product. Sort them in + /// the order of descending power. + /// + /// (x*x) -> [(x, 2)] + /// ((x*x)*x) -> [(x, 3)] + /// ((((x*y)*x)*y)*x) -> [(x, 3), (y, 2)] + /// + /// \returns Whether any factors have a power greater than one. + static bool collectMultiplyFactors(SmallVectorImpl &Ops, + SmallVectorImpl &Factors) { + // FIXME: Have Ops be (ValueEntry, Multiplicity) pairs, simplifying this. + // Compute the sum of powers of simplifiable factors. + unsigned FactorPowerSum = 0; + for (unsigned Idx = 1, Size = Ops.size(); Idx < Size; ++Idx) { + Value *Op = Ops[Idx-1].Op; + + // Count the number of occurrences of this value. + unsigned Count = 1; + for (; Idx < Size && Ops[Idx].Op == Op; ++Idx) + ++Count; + // Track for simplification all factors which occur 2 or more times. + if (Count > 1) + FactorPowerSum += Count; + } + + // We can only simplify factors if the sum of the powers of our simplifiable + // factors is 4 or higher. When that is the case, we will *always* have + // a simplification. This is an important invariant to prevent cyclicly + // trying to simplify already minimal formations. + if (FactorPowerSum < 4) + return false; + + // Now gather the simplifiable factors, removing them from Ops. + FactorPowerSum = 0; + for (unsigned Idx = 1; Idx < Ops.size(); ++Idx) { + Value *Op = Ops[Idx-1].Op; + + // Count the number of occurrences of this value. + unsigned Count = 1; + for (; Idx < Ops.size() && Ops[Idx].Op == Op; ++Idx) + ++Count; + if (Count == 1) + continue; + // Move an even number of occurrences to Factors. + Count &= ~1U; + Idx -= Count; + FactorPowerSum += Count; + Factors.push_back(Factor(Op, Count)); + Ops.erase(Ops.begin()+Idx, Ops.begin()+Idx+Count); + } + + // None of the adjustments above should have reduced the sum of factor powers + // below our mininum of '4'. + assert(FactorPowerSum >= 4); + + llvm::stable_sort(Factors, [](const Factor &LHS, const Factor &RHS) { + return LHS.Power > RHS.Power; + }); + return true; + } + + /// Build a tree of multiplies, computing the product of Ops. + static Value *buildMultiplyTree(IRBuilder<> &Builder, + SmallVectorImpl &Ops) { + if (Ops.size() == 1) + return Ops.back(); + + Value *LHS = Ops.pop_back_val(); + do { + if (LHS->getType()->isIntOrIntVectorTy()) + LHS = Builder.CreateMul(LHS, Ops.pop_back_val()); + else + LHS = Builder.CreateFMul(LHS, Ops.pop_back_val()); + } while (!Ops.empty()); + + return LHS; + } + + /// Build a minimal multiplication DAG for (a^x)*(b^y)*(c^z)*... + /// + /// Given a vector of values raised to various powers, where no two values are + /// equal and the powers are sorted in decreasing order, compute the minimal + /// DAG of multiplies to compute the final product, and return that product + /// value. + Value * + ReassociatePass::buildMinimalMultiplyDAG(IRBuilder<> &Builder, + SmallVectorImpl &Factors) { + assert(Factors[0].Power); + SmallVector OuterProduct; + for (unsigned LastIdx = 0, Idx = 1, Size = Factors.size(); + Idx < Size && Factors[Idx].Power > 0; ++Idx) { + if (Factors[Idx].Power != Factors[LastIdx].Power) { + LastIdx = Idx; + continue; + } + + // We want to multiply across all the factors with the same power so that + // we can raise them to that power as a single entity. Build a mini tree + // for that. + SmallVector InnerProduct; + InnerProduct.push_back(Factors[LastIdx].Base); + do { + InnerProduct.push_back(Factors[Idx].Base); + ++Idx; + } while (Idx < Size && Factors[Idx].Power == Factors[LastIdx].Power); + + // Reset the base value of the first factor to the new expression tree. + // We'll remove all the factors with the same power in a second pass. + Value *M = Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct); + if (Instruction *MI = dyn_cast(M)) + RedoInsts.insert(MI); + + LastIdx = Idx; + } + // Unique factors with equal powers -- we've folded them into the first one's + // base. + Factors.erase(std::unique(Factors.begin(), Factors.end(), + [](const Factor &LHS, const Factor &RHS) { + return LHS.Power == RHS.Power; + }), + Factors.end()); + + // Iteratively collect the base of each factor with an add power into the + // outer product, and halve each power in preparation for squaring the + // expression. + for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) { + if (Factors[Idx].Power & 1) + OuterProduct.push_back(Factors[Idx].Base); + Factors[Idx].Power >>= 1; + } + if (Factors[0].Power) { + Value *SquareRoot = buildMinimalMultiplyDAG(Builder, Factors); + OuterProduct.push_back(SquareRoot); + OuterProduct.push_back(SquareRoot); + } + if (OuterProduct.size() == 1) + return OuterProduct.front(); + + Value *V = buildMultiplyTree(Builder, OuterProduct); + return V; + } + + Value *ReassociatePass::OptimizeMul(BinaryOperator *I, + SmallVectorImpl &Ops) { + // We can only optimize the multiplies when there is a chain of more than + // three, such that a balanced tree might require fewer total multiplies. + if (Ops.size() < 4) + return nullptr; + + // Try to turn linear trees of multiplies without other uses of the + // intermediate stages into minimal multiply DAGs with perfect sub-expression + // re-use. + SmallVector Factors; + if (!collectMultiplyFactors(Ops, Factors)) + return nullptr; // All distinct factors, so nothing left for us to do. + + IRBuilder<> Builder(I); + // The reassociate transformation for FP operations is performed only + // if unsafe algebra is permitted by FastMathFlags. Propagate those flags + // to the newly generated operations. + if (auto FPI = dyn_cast(I)) + Builder.setFastMathFlags(FPI->getFastMathFlags()); + + Value *V = buildMinimalMultiplyDAG(Builder, Factors); + if (Ops.empty()) + return V; + + ValueEntry NewEntry = ValueEntry(getRank(V), V); + Ops.insert(llvm::lower_bound(Ops, NewEntry), NewEntry); + return nullptr; + } + + Value *ReassociatePass::OptimizeExpression(BinaryOperator *I, + SmallVectorImpl &Ops) { + // Now that we have the linearized expression tree, try to optimize it. + // Start by folding any constants that we found. + Constant *Cst = nullptr; + unsigned Opcode = I->getOpcode(); + while (!Ops.empty() && isa(Ops.back().Op)) { + Constant *C = cast(Ops.pop_back_val().Op); + Cst = Cst ? ConstantExpr::get(Opcode, C, Cst) : C; + } + // If there was nothing but constants then we are done. + if (Ops.empty()) + return Cst; + + // Put the combined constant back at the end of the operand list, except if + // there is no point. For example, an add of 0 gets dropped here, while a + // multiplication by zero turns the whole expression into zero. + if (Cst && Cst != ConstantExpr::getBinOpIdentity(Opcode, I->getType())) { + if (Cst == ConstantExpr::getBinOpAbsorber(Opcode, I->getType())) + return Cst; + Ops.push_back(ValueEntry(0, Cst)); + } + + if (Ops.size() == 1) return Ops[0].Op; + + // Handle destructive annihilation due to identities between elements in the + // argument list here. + unsigned NumOps = Ops.size(); + switch (Opcode) { + default: break; + case Instruction::And: + case Instruction::Or: + if (Value *Result = OptimizeAndOrXor(Opcode, Ops)) + return Result; + break; + + case Instruction::Xor: + if (Value *Result = OptimizeXor(I, Ops)) + return Result; + break; + + case Instruction::Add: + case Instruction::FAdd: + if (Value *Result = OptimizeAdd(I, Ops)) + return Result; + break; + + case Instruction::Mul: + case Instruction::FMul: + if (Value *Result = OptimizeMul(I, Ops)) + return Result; + break; + } + + if (Ops.size() != NumOps) + return OptimizeExpression(I, Ops); + return nullptr; + } + + // Remove dead instructions and if any operands are trivially dead add them to + // Insts so they will be removed as well. + void ReassociatePass::RecursivelyEraseDeadInsts(Instruction *I, + OrderedSet &Insts) { + assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!"); + SmallVector Ops(I->op_begin(), I->op_end()); + ValueRankMap.erase(I); + Insts.remove(I); + RedoInsts.remove(I); ++ llvm::salvageDebugInfoOrMarkUndef(*I); + I->eraseFromParent(); + for (auto Op : Ops) + if (Instruction *OpInst = dyn_cast(Op)) + if (OpInst->use_empty()) + Insts.insert(OpInst); + } + + /// Zap the given instruction, adding interesting operands to the work list. + void ReassociatePass::EraseInst(Instruction *I) { + assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!"); + LLVM_DEBUG(dbgs() << "Erasing dead inst: "; I->dump()); + + SmallVector Ops(I->op_begin(), I->op_end()); + // Erase the dead instruction. + ValueRankMap.erase(I); + RedoInsts.remove(I); ++ llvm::salvageDebugInfoOrMarkUndef(*I); + I->eraseFromParent(); + // Optimize its operands. + SmallPtrSet Visited; // Detect self-referential nodes. + for (unsigned i = 0, e = Ops.size(); i != e; ++i) + if (Instruction *Op = dyn_cast(Ops[i])) { + // If this is a node in an expression tree, climb to the expression root + // and add that since that's where optimization actually happens. + unsigned Opcode = Op->getOpcode(); + while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode && + Visited.insert(Op).second) + Op = Op->user_back(); + + // The instruction we're going to push may be coming from a + // dead block, and Reassociate skips the processing of unreachable + // blocks because it's a waste of time and also because it can + // lead to infinite loop due to LLVM's non-standard definition + // of dominance. + if (ValueRankMap.find(Op) != ValueRankMap.end()) + RedoInsts.insert(Op); + } + + MadeChange = true; + } + + /// Recursively analyze an expression to build a list of instructions that have + /// negative floating-point constant operands. The caller can then transform + /// the list to create positive constants for better reassociation and CSE. + static void getNegatibleInsts(Value *V, + SmallVectorImpl &Candidates) { + // Handle only one-use instructions. Combining negations does not justify + // replicating instructions. + Instruction *I; + if (!match(V, m_OneUse(m_Instruction(I)))) + return; + + // Handle expressions of multiplications and divisions. + // TODO: This could look through floating-point casts. + const APFloat *C; + switch (I->getOpcode()) { + case Instruction::FMul: + // Not expecting non-canonical code here. Bail out and wait. + if (match(I->getOperand(0), m_Constant())) + break; + + if (match(I->getOperand(1), m_APFloat(C)) && C->isNegative()) { + Candidates.push_back(I); + LLVM_DEBUG(dbgs() << "FMul with negative constant: " << *I << '\n'); + } + getNegatibleInsts(I->getOperand(0), Candidates); + getNegatibleInsts(I->getOperand(1), Candidates); + break; + case Instruction::FDiv: + // Not expecting non-canonical code here. Bail out and wait. + if (match(I->getOperand(0), m_Constant()) && + match(I->getOperand(1), m_Constant())) + break; + + if ((match(I->getOperand(0), m_APFloat(C)) && C->isNegative()) || + (match(I->getOperand(1), m_APFloat(C)) && C->isNegative())) { + Candidates.push_back(I); + LLVM_DEBUG(dbgs() << "FDiv with negative constant: " << *I << '\n'); + } + getNegatibleInsts(I->getOperand(0), Candidates); + getNegatibleInsts(I->getOperand(1), Candidates); + break; + default: + break; + } + } + + /// Given an fadd/fsub with an operand that is a one-use instruction + /// (the fadd/fsub), try to change negative floating-point constants into + /// positive constants to increase potential for reassociation and CSE. + Instruction *ReassociatePass::canonicalizeNegFPConstantsForOp(Instruction *I, + Instruction *Op, + Value *OtherOp) { + assert((I->getOpcode() == Instruction::FAdd || + I->getOpcode() == Instruction::FSub) && "Expected fadd/fsub"); + + // Collect instructions with negative FP constants from the subtree that ends + // in Op. + SmallVector Candidates; + getNegatibleInsts(Op, Candidates); + if (Candidates.empty()) + return nullptr; + + // Don't canonicalize x + (-Constant * y) -> x - (Constant * y), if the + // resulting subtract will be broken up later. This can get us into an + // infinite loop during reassociation. + bool IsFSub = I->getOpcode() == Instruction::FSub; + bool NeedsSubtract = !IsFSub && Candidates.size() % 2 == 1; + if (NeedsSubtract && ShouldBreakUpSubtract(I)) + return nullptr; + + for (Instruction *Negatible : Candidates) { + const APFloat *C; + if (match(Negatible->getOperand(0), m_APFloat(C))) { + assert(!match(Negatible->getOperand(1), m_Constant()) && + "Expecting only 1 constant operand"); + assert(C->isNegative() && "Expected negative FP constant"); + Negatible->setOperand(0, ConstantFP::get(Negatible->getType(), abs(*C))); + MadeChange = true; + } + if (match(Negatible->getOperand(1), m_APFloat(C))) { + assert(!match(Negatible->getOperand(0), m_Constant()) && + "Expecting only 1 constant operand"); + assert(C->isNegative() && "Expected negative FP constant"); + Negatible->setOperand(1, ConstantFP::get(Negatible->getType(), abs(*C))); + MadeChange = true; + } + } + assert(MadeChange == true && "Negative constant candidate was not changed"); + + // Negations cancelled out. + if (Candidates.size() % 2 == 0) + return I; + + // Negate the final operand in the expression by flipping the opcode of this + // fadd/fsub. + assert(Candidates.size() % 2 == 1 && "Expected odd number"); + IRBuilder<> Builder(I); + Value *NewInst = IsFSub ? Builder.CreateFAddFMF(OtherOp, Op, I) + : Builder.CreateFSubFMF(OtherOp, Op, I); + I->replaceAllUsesWith(NewInst); + RedoInsts.insert(I); + return dyn_cast(NewInst); + } + + /// Canonicalize expressions that contain a negative floating-point constant + /// of the following form: + /// OtherOp + (subtree) -> OtherOp {+/-} (canonical subtree) + /// (subtree) + OtherOp -> OtherOp {+/-} (canonical subtree) + /// OtherOp - (subtree) -> OtherOp {+/-} (canonical subtree) + /// + /// The fadd/fsub opcode may be switched to allow folding a negation into the + /// input instruction. + Instruction *ReassociatePass::canonicalizeNegFPConstants(Instruction *I) { + LLVM_DEBUG(dbgs() << "Combine negations for: " << *I << '\n'); + Value *X; + Instruction *Op; + if (match(I, m_FAdd(m_Value(X), m_OneUse(m_Instruction(Op))))) + if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X)) + I = R; + if (match(I, m_FAdd(m_OneUse(m_Instruction(Op)), m_Value(X)))) + if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X)) + I = R; + if (match(I, m_FSub(m_Value(X), m_OneUse(m_Instruction(Op))))) + if (Instruction *R = canonicalizeNegFPConstantsForOp(I, Op, X)) + I = R; + return I; + } + + /// Inspect and optimize the given instruction. Note that erasing + /// instructions is not allowed. + void ReassociatePass::OptimizeInst(Instruction *I) { + // Only consider operations that we understand. + if (!isa(I) && !isa(I)) + return; + + if (I->getOpcode() == Instruction::Shl && isa(I->getOperand(1))) + // If an operand of this shift is a reassociable multiply, or if the shift + // is used by a reassociable multiply or add, turn into a multiply. + if (isReassociableOp(I->getOperand(0), Instruction::Mul) || + (I->hasOneUse() && + (isReassociableOp(I->user_back(), Instruction::Mul) || + isReassociableOp(I->user_back(), Instruction::Add)))) { + Instruction *NI = ConvertShiftToMul(I); + RedoInsts.insert(I); + MadeChange = true; + I = NI; + } + + // Commute binary operators, to canonicalize the order of their operands. + // This can potentially expose more CSE opportunities, and makes writing other + // transformations simpler. + if (I->isCommutative()) + canonicalizeOperands(I); + + // Canonicalize negative constants out of expressions. + if (Instruction *Res = canonicalizeNegFPConstants(I)) + I = Res; + + // Don't optimize floating-point instructions unless they are 'fast'. + if (I->getType()->isFPOrFPVectorTy() && !I->isFast()) + return; + + // Do not reassociate boolean (i1) expressions. We want to preserve the + // original order of evaluation for short-circuited comparisons that + // SimplifyCFG has folded to AND/OR expressions. If the expression + // is not further optimized, it is likely to be transformed back to a + // short-circuited form for code gen, and the source order may have been + // optimized for the most likely conditions. + if (I->getType()->isIntegerTy(1)) + return; + + // If this is a subtract instruction which is not already in negate form, + // see if we can convert it to X+-Y. + if (I->getOpcode() == Instruction::Sub) { + if (ShouldBreakUpSubtract(I)) { + Instruction *NI = BreakUpSubtract(I, RedoInsts); + RedoInsts.insert(I); + MadeChange = true; + I = NI; + } else if (match(I, m_Neg(m_Value()))) { + // Otherwise, this is a negation. See if the operand is a multiply tree + // and if this is not an inner node of a multiply tree. + if (isReassociableOp(I->getOperand(1), Instruction::Mul) && + (!I->hasOneUse() || + !isReassociableOp(I->user_back(), Instruction::Mul))) { + Instruction *NI = LowerNegateToMultiply(I); + // If the negate was simplified, revisit the users to see if we can + // reassociate further. + for (User *U : NI->users()) { + if (BinaryOperator *Tmp = dyn_cast(U)) + RedoInsts.insert(Tmp); + } + RedoInsts.insert(I); + MadeChange = true; + I = NI; + } + } + } else if (I->getOpcode() == Instruction::FNeg || + I->getOpcode() == Instruction::FSub) { + if (ShouldBreakUpSubtract(I)) { + Instruction *NI = BreakUpSubtract(I, RedoInsts); + RedoInsts.insert(I); + MadeChange = true; + I = NI; + } else if (match(I, m_FNeg(m_Value()))) { + // Otherwise, this is a negation. See if the operand is a multiply tree + // and if this is not an inner node of a multiply tree. + Value *Op = isa(I) ? I->getOperand(1) : + I->getOperand(0); + if (isReassociableOp(Op, Instruction::FMul) && + (!I->hasOneUse() || + !isReassociableOp(I->user_back(), Instruction::FMul))) { + // If the negate was simplified, revisit the users to see if we can + // reassociate further. + Instruction *NI = LowerNegateToMultiply(I); + for (User *U : NI->users()) { + if (BinaryOperator *Tmp = dyn_cast(U)) + RedoInsts.insert(Tmp); + } + RedoInsts.insert(I); + MadeChange = true; + I = NI; + } + } + } + + // If this instruction is an associative binary operator, process it. + if (!I->isAssociative()) return; + BinaryOperator *BO = cast(I); + + // If this is an interior node of a reassociable tree, ignore it until we + // get to the root of the tree, to avoid N^2 analysis. + unsigned Opcode = BO->getOpcode(); + if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode) { + // During the initial run we will get to the root of the tree. + // But if we get here while we are redoing instructions, there is no + // guarantee that the root will be visited. So Redo later + if (BO->user_back() != BO && + BO->getParent() == BO->user_back()->getParent()) + RedoInsts.insert(BO->user_back()); + return; + } + + // If this is an add tree that is used by a sub instruction, ignore it + // until we process the subtract. + if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add && + cast(BO->user_back())->getOpcode() == Instruction::Sub) + return; + if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd && + cast(BO->user_back())->getOpcode() == Instruction::FSub) + return; + + ReassociateExpression(BO); + } + + void ReassociatePass::ReassociateExpression(BinaryOperator *I) { + // First, walk the expression tree, linearizing the tree, collecting the + // operand information. + SmallVector Tree; + MadeChange |= LinearizeExprTree(I, Tree); + SmallVector Ops; + Ops.reserve(Tree.size()); + for (unsigned i = 0, e = Tree.size(); i != e; ++i) { + RepeatedValue E = Tree[i]; + Ops.append(E.second.getZExtValue(), + ValueEntry(getRank(E.first), E.first)); + } + + LLVM_DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n'); + + // Now that we have linearized the tree to a list and have gathered all of + // the operands and their ranks, sort the operands by their rank. Use a + // stable_sort so that values with equal ranks will have their relative + // positions maintained (and so the compiler is deterministic). Note that + // this sorts so that the highest ranking values end up at the beginning of + // the vector. + llvm::stable_sort(Ops); + + // Now that we have the expression tree in a convenient + // sorted form, optimize it globally if possible. + if (Value *V = OptimizeExpression(I, Ops)) { + if (V == I) + // Self-referential expression in unreachable code. + return; + // This expression tree simplified to something that isn't a tree, + // eliminate it. + LLVM_DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n'); + I->replaceAllUsesWith(V); + if (Instruction *VI = dyn_cast(V)) + if (I->getDebugLoc()) + VI->setDebugLoc(I->getDebugLoc()); + RedoInsts.insert(I); + ++NumAnnihil; + return; + } + + // We want to sink immediates as deeply as possible except in the case where + // this is a multiply tree used only by an add, and the immediate is a -1. + // In this case we reassociate to put the negation on the outside so that we + // can fold the negation into the add: (-X)*Y + Z -> Z-X*Y + if (I->hasOneUse()) { + if (I->getOpcode() == Instruction::Mul && + cast(I->user_back())->getOpcode() == Instruction::Add && + isa(Ops.back().Op) && + cast(Ops.back().Op)->isMinusOne()) { + ValueEntry Tmp = Ops.pop_back_val(); + Ops.insert(Ops.begin(), Tmp); + } else if (I->getOpcode() == Instruction::FMul && + cast(I->user_back())->getOpcode() == + Instruction::FAdd && + isa(Ops.back().Op) && + cast(Ops.back().Op)->isExactlyValue(-1.0)) { + ValueEntry Tmp = Ops.pop_back_val(); + Ops.insert(Ops.begin(), Tmp); + } + } + + LLVM_DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n'); + + if (Ops.size() == 1) { + if (Ops[0].Op == I) + // Self-referential expression in unreachable code. + return; + + // This expression tree simplified to something that isn't a tree, + // eliminate it. + I->replaceAllUsesWith(Ops[0].Op); + if (Instruction *OI = dyn_cast(Ops[0].Op)) + OI->setDebugLoc(I->getDebugLoc()); + RedoInsts.insert(I); + return; + } + + if (Ops.size() > 2 && Ops.size() <= GlobalReassociateLimit) { + // Find the pair with the highest count in the pairmap and move it to the + // back of the list so that it can later be CSE'd. + // example: + // a*b*c*d*e + // if c*e is the most "popular" pair, we can express this as + // (((c*e)*d)*b)*a + unsigned Max = 1; + unsigned BestRank = 0; + std::pair BestPair; + unsigned Idx = I->getOpcode() - Instruction::BinaryOpsBegin; + for (unsigned i = 0; i < Ops.size() - 1; ++i) + for (unsigned j = i + 1; j < Ops.size(); ++j) { + unsigned Score = 0; + Value *Op0 = Ops[i].Op; + Value *Op1 = Ops[j].Op; + if (std::less()(Op1, Op0)) + std::swap(Op0, Op1); + auto it = PairMap[Idx].find({Op0, Op1}); + if (it != PairMap[Idx].end()) { + // Functions like BreakUpSubtract() can erase the Values we're using + // as keys and create new Values after we built the PairMap. There's a + // small chance that the new nodes can have the same address as + // something already in the table. We shouldn't accumulate the stored + // score in that case as it refers to the wrong Value. + if (it->second.isValid()) + Score += it->second.Score; + } + + unsigned MaxRank = std::max(Ops[i].Rank, Ops[j].Rank); + if (Score > Max || (Score == Max && MaxRank < BestRank)) { + BestPair = {i, j}; + Max = Score; + BestRank = MaxRank; + } + } + if (Max > 1) { + auto Op0 = Ops[BestPair.first]; + auto Op1 = Ops[BestPair.second]; + Ops.erase(&Ops[BestPair.second]); + Ops.erase(&Ops[BestPair.first]); + Ops.push_back(Op0); + Ops.push_back(Op1); + } + } + // Now that we ordered and optimized the expressions, splat them back into + // the expression tree, removing any unneeded nodes. + RewriteExprTree(I, Ops); + } + + void + ReassociatePass::BuildPairMap(ReversePostOrderTraversal &RPOT) { + // Make a "pairmap" of how often each operand pair occurs. + for (BasicBlock *BI : RPOT) { + for (Instruction &I : *BI) { + if (!I.isAssociative()) + continue; + + // Ignore nodes that aren't at the root of trees. + if (I.hasOneUse() && I.user_back()->getOpcode() == I.getOpcode()) + continue; + + // Collect all operands in a single reassociable expression. + // Since Reassociate has already been run once, we can assume things + // are already canonical according to Reassociation's regime. + SmallVector Worklist = { I.getOperand(0), I.getOperand(1) }; + SmallVector Ops; + while (!Worklist.empty() && Ops.size() <= GlobalReassociateLimit) { + Value *Op = Worklist.pop_back_val(); + Instruction *OpI = dyn_cast(Op); + if (!OpI || OpI->getOpcode() != I.getOpcode() || !OpI->hasOneUse()) { + Ops.push_back(Op); + continue; + } + // Be paranoid about self-referencing expressions in unreachable code. + if (OpI->getOperand(0) != OpI) + Worklist.push_back(OpI->getOperand(0)); + if (OpI->getOperand(1) != OpI) + Worklist.push_back(OpI->getOperand(1)); + } + // Skip extremely long expressions. + if (Ops.size() > GlobalReassociateLimit) + continue; + + // Add all pairwise combinations of operands to the pair map. + unsigned BinaryIdx = I.getOpcode() - Instruction::BinaryOpsBegin; + SmallSet, 32> Visited; + for (unsigned i = 0; i < Ops.size() - 1; ++i) { + for (unsigned j = i + 1; j < Ops.size(); ++j) { + // Canonicalize operand orderings. + Value *Op0 = Ops[i]; + Value *Op1 = Ops[j]; + if (std::less()(Op1, Op0)) + std::swap(Op0, Op1); + if (!Visited.insert({Op0, Op1}).second) + continue; + auto res = PairMap[BinaryIdx].insert({{Op0, Op1}, {Op0, Op1, 1}}); + if (!res.second) { + // If either key value has been erased then we've got the same + // address by coincidence. That can't happen here because nothing is + // erasing values but it can happen by the time we're querying the + // map. + assert(res.first->second.isValid() && "WeakVH invalidated"); + ++res.first->second.Score; + } + } + } + } + } + } + + PreservedAnalyses ReassociatePass::run(Function &F, FunctionAnalysisManager &) { + // Get the functions basic blocks in Reverse Post Order. This order is used by + // BuildRankMap to pre calculate ranks correctly. It also excludes dead basic + // blocks (it has been seen that the analysis in this pass could hang when + // analysing dead basic blocks). + ReversePostOrderTraversal RPOT(&F); + + // Calculate the rank map for F. + BuildRankMap(F, RPOT); + + // Build the pair map before running reassociate. + // Technically this would be more accurate if we did it after one round + // of reassociation, but in practice it doesn't seem to help much on + // real-world code, so don't waste the compile time running reassociate + // twice. + // If a user wants, they could expicitly run reassociate twice in their + // pass pipeline for further potential gains. + // It might also be possible to update the pair map during runtime, but the + // overhead of that may be large if there's many reassociable chains. + BuildPairMap(RPOT); + + MadeChange = false; + + // Traverse the same blocks that were analysed by BuildRankMap. + for (BasicBlock *BI : RPOT) { + assert(RankMap.count(&*BI) && "BB should be ranked."); + // Optimize every instruction in the basic block. + for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;) + if (isInstructionTriviallyDead(&*II)) { + EraseInst(&*II++); + } else { + OptimizeInst(&*II); + assert(II->getParent() == &*BI && "Moved to a different block!"); + ++II; + } + + // Make a copy of all the instructions to be redone so we can remove dead + // instructions. + OrderedSet ToRedo(RedoInsts); + // Iterate over all instructions to be reevaluated and remove trivially dead + // instructions. If any operand of the trivially dead instruction becomes + // dead mark it for deletion as well. Continue this process until all + // trivially dead instructions have been removed. + while (!ToRedo.empty()) { + Instruction *I = ToRedo.pop_back_val(); + if (isInstructionTriviallyDead(I)) { + RecursivelyEraseDeadInsts(I, ToRedo); + MadeChange = true; + } + } + + // Now that we have removed dead instructions, we can reoptimize the + // remaining instructions. + while (!RedoInsts.empty()) { + Instruction *I = RedoInsts.front(); + RedoInsts.erase(RedoInsts.begin()); + if (isInstructionTriviallyDead(I)) + EraseInst(I); + else + OptimizeInst(I); + } + } + + // We are done with the rank map and pair map. + RankMap.clear(); + ValueRankMap.clear(); + for (auto &Entry : PairMap) + Entry.clear(); + + if (MadeChange) { + PreservedAnalyses PA; + PA.preserveSet(); + PA.preserve(); + return PA; + } + + return PreservedAnalyses::all(); + } + + namespace { + + class ReassociateLegacyPass : public FunctionPass { + ReassociatePass Impl; + + public: + static char ID; // Pass identification, replacement for typeid + + ReassociateLegacyPass() : FunctionPass(ID) { + initializeReassociateLegacyPassPass(*PassRegistry::getPassRegistry()); + } + + bool runOnFunction(Function &F) override { + if (skipFunction(F)) + return false; + + FunctionAnalysisManager DummyFAM; + auto PA = Impl.run(F, DummyFAM); + return !PA.areAllPreserved(); + } + + void getAnalysisUsage(AnalysisUsage &AU) const override { + AU.setPreservesCFG(); + AU.addPreserved(); + } + }; + + } // end anonymous namespace + + char ReassociateLegacyPass::ID = 0; + + INITIALIZE_PASS(ReassociateLegacyPass, "reassociate", + "Reassociate expressions", false, false) + + // Public interface to the Reassociate pass + FunctionPass *llvm::createReassociatePass() { + return new ReassociateLegacyPass(); + } diff --git a/llvm/test/Transforms/Reassociate/reassociate_salvages_debug_info.ll b/llvm/test/Transforms/Reassociate/reassociate_salvages_debug_info.ll new file mode 100644 index 000000000000..34e0b9a04bb3 --- /dev/null +++ b/llvm/test/Transforms/Reassociate/reassociate_salvages_debug_info.ll @@ -0,0 +1,50 @@ +; RUN: opt < %s -reassociate -S | FileCheck %s + +; Check that reassociate pass now salvages debug info when dropping instructions. + +define hidden i32 @main(i32 %argc, i8** %argv) { +entry: + ; CHECK: call void @llvm.dbg.value(metadata i32 %argc, metadata [[VAR_B:![0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 1, DW_OP_stack_value)) + %add = add nsw i32 %argc, 1, !dbg !26 + call void @llvm.dbg.value(metadata i32 %add, metadata !22, metadata !DIExpression()), !dbg !25 + %add1 = add nsw i32 %argc, %add, !dbg !27 + ret i32 %add1, !dbg !28 +} + +declare void @llvm.dbg.declare(metadata, metadata, metadata) #1 +declare void @llvm.dbg.value(metadata, metadata, metadata) #1 + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!3, !4, !5, !6} +!llvm.ident = !{!7} + +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, debugInfoForProfiling: true, nameTableKind: None) +!1 = !DIFile(filename: "test2.cpp", directory: "C:\") +!2 = !{} +!3 = !{i32 2, !"Dwarf Version", i32 4} +!4 = !{i32 2, !"Debug Info Version", i32 3} +!5 = !{i32 1, !"wchar_size", i32 2} +!6 = !{i32 7, !"PIC Level", i32 2} +!7 = !{!"clang version 10.0.0"} +!8 = distinct !DISubprogram(name: "main", scope: !9, file: !9, line: 1, type: !10, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !18) +!9 = !DIFile(filename: "./test2.cpp", directory: "C:\") +!10 = !DISubroutineType(types: !11) +!11 = !{!12, !13, !14} +!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!13 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !12) +!14 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !15, size: 64) +!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64) +!16 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !17) +!17 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char) +!18 = !{!19, !20, !21, !22, !23, !24} +!19 = !DILocalVariable(name: "argc", arg: 1, scope: !8, file: !9, line: 1, type: !13) +!20 = !DILocalVariable(name: "argv", arg: 2, scope: !8, file: !9, line: 1, type: !14) +!21 = !DILocalVariable(name: "a", scope: !8, file: !9, line: 2, type: !12) +; CHECK: [[VAR_B]] = !DILocalVariable(name: "b" +!22 = !DILocalVariable(name: "b", scope: !8, file: !9, line: 3, type: !12) +!23 = !DILocalVariable(name: "to_return", scope: !8, file: !9, line: 4, type: !12) +!24 = !DILocalVariable(name: "result", scope: !8, file: !9, line: 5, type: !12) +!25 = !DILocation(line: 0, scope: !8) +!26 = !DILocation(line: 3, scope: !8) +!27 = !DILocation(line: 4, scope: !8) +!28 = !DILocation(line: 6, scope: !8) diff --git a/llvm/test/Transforms/Reassociate/undef_intrinsics_when_deleting_instructions.ll b/llvm/test/Transforms/Reassociate/undef_intrinsics_when_deleting_instructions.ll new file mode 100644 index 000000000000..98c51c5cf8bb --- /dev/null +++ b/llvm/test/Transforms/Reassociate/undef_intrinsics_when_deleting_instructions.ll @@ -0,0 +1,95 @@ +; RUN: opt < %s -reassociate -S | FileCheck %s + +; Check that reassociate pass now undefs debug intrinsics that reference a value +; that gets dropped and cannot be salvaged. + +define hidden i32 @main() local_unnamed_addr { +entry: + %foo = alloca i32, align 4, !dbg !20 + %foo.0.foo.0..sroa_cast = bitcast i32* %foo to i8*, !dbg !20 + call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %foo.0.foo.0..sroa_cast), !dbg !20 + store volatile i32 4, i32* %foo, align 4, !dbg !20, !tbaa !21 + %foo.0.foo.0. = load volatile i32, i32* %foo, align 4, !dbg !25, !tbaa !21 + %foo.0.foo.0.15 = load volatile i32, i32* %foo, align 4, !dbg !27, !tbaa !21 + %foo.0.foo.0.16 = load volatile i32, i32* %foo, align 4, !dbg !28, !tbaa !21 + ; CHECK-NOT: %add = add nsw i32 %foo.0.foo.0., %foo.0.foo.0.15 + %add = add nsw i32 %foo.0.foo.0., %foo.0.foo.0.15, !dbg !29 + ; CHECK: call void @llvm.dbg.value(metadata i32 undef, metadata [[VAR_A:![0-9]+]], metadata !DIExpression()) + call void @llvm.dbg.value(metadata i32 %add, metadata !19, metadata !DIExpression()), !dbg !26 + %foo.0.foo.0.17 = load volatile i32, i32* %foo, align 4, !dbg !30, !tbaa !21 + %cmp = icmp eq i32 %foo.0.foo.0.17, 4, !dbg !30 + br i1 %cmp, label %if.then, label %if.end, !dbg !32 + + ; CHECK-LABEL: if.then: +if.then: + ; CHECK-NOT: %add1 = add nsw i32 %add, %foo.0.foo.0.16 + %add1 = add nsw i32 %add, %foo.0.foo.0.16, !dbg !33 + ; CHECK: call void @llvm.dbg.value(metadata i32 undef, metadata [[VAR_A]], metadata !DIExpression()) + call void @llvm.dbg.value(metadata i32 %add1, metadata !19, metadata !DIExpression()), !dbg !26 + ; CHECK: call void @llvm.dbg.value(metadata i32 undef, metadata [[VAR_CHEESE:![0-9]+]], metadata !DIExpression()) + call void @llvm.dbg.value(metadata i32 %add, metadata !18, metadata !DIExpression()), !dbg !26 + %sub = add nsw i32 %add, -12, !dbg !34 + %sub3 = sub nsw i32 %add1, %sub, !dbg !34 + %mul = mul nsw i32 %sub3, 20, !dbg !36 + %div = sdiv i32 %mul, 3, !dbg !37 + br label %if.end, !dbg !38 + +if.end: + %a.0 = phi i32 [ %div, %if.then ], [ 0, %entry ], !dbg !39 + call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %foo.0.foo.0..sroa_cast), !dbg !40 + ret i32 %a.0, !dbg !41 +} + +declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #1 +declare void @llvm.dbg.declare(metadata, metadata, metadata) #2 +declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #1 +declare void @llvm.dbg.value(metadata, metadata, metadata) #2 + +!llvm.dbg.cu = !{!0} +!llvm.module.flags = !{!3, !4, !5, !6} +!llvm.ident = !{!7} + +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, debugInfoForProfiling: true, nameTableKind: None) +!1 = !DIFile(filename: "test.cpp", directory: "F:\") +!2 = !{} +!3 = !{i32 2, !"Dwarf Version", i32 4} +!4 = !{i32 2, !"Debug Info Version", i32 3} +!5 = !{i32 1, !"wchar_size", i32 2} +!6 = !{i32 7, !"PIC Level", i32 2} +!7 = !{!"clang version 10.0.0"} +!8 = distinct !DISubprogram(name: "main", scope: !9, file: !9, line: 1, type: !10, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !13) +!9 = !DIFile(filename: "./test.cpp", directory: "F:\") +!10 = !DISubroutineType(types: !11) +!11 = !{!12} +!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed) +!13 = !{!14, !16, !17, !18, !19} +!14 = !DILocalVariable(name: "foo", scope: !8, file: !9, line: 2, type: !15) +!15 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !12) +!16 = !DILocalVariable(name: "read1", scope: !8, file: !9, line: 3, type: !12) +!17 = !DILocalVariable(name: "read2", scope: !8, file: !9, line: 4, type: !12) +; CHECK: [[VAR_CHEESE]] = !DILocalVariable(name: "cheese" +!18 = !DILocalVariable(name: "cheese", scope: !8, file: !9, line: 6, type: !12) +; CHECK: [[VAR_A]] = !DILocalVariable(name: "a" +!19 = !DILocalVariable(name: "a", scope: !8, file: !9, line: 7, type: !12) +!20 = !DILocation(line: 2, scope: !8) +!21 = !{!22, !22, i64 0} +!22 = !{!"int", !23, i64 0} +!23 = !{!"omnipotent char", !24, i64 0} +!24 = !{!"Simple C++ TBAA"} +!25 = !DILocation(line: 3, scope: !8) +!26 = !DILocation(line: 0, scope: !8) +!27 = !DILocation(line: 4, scope: !8) +!28 = !DILocation(line: 6, scope: !8) +!29 = !DILocation(line: 7, scope: !8) +!30 = !DILocation(line: 10, scope: !31) +!31 = distinct !DILexicalBlock(scope: !8, file: !9, line: 10) +!32 = !DILocation(line: 10, scope: !8) +!33 = !DILocation(line: 8, scope: !8) +!34 = !DILocation(line: 12, scope: !35) +!35 = distinct !DILexicalBlock(scope: !31, file: !9, line: 10) +!36 = !DILocation(line: 13, scope: !35) +!37 = !DILocation(line: 14, scope: !35) +!38 = !DILocation(line: 15, scope: !35) +!39 = !DILocation(line: 0, scope: !31) +!40 = !DILocation(line: 20, scope: !8) +!41 = !DILocation(line: 19, scope: !8)