| //===- 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/BasicAliasAnalysis.h" |
| #include "llvm/Analysis/GlobalsModRef.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/InitializePasses.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 "llvm/Transforms/Utils/Local.h" |
| #include <algorithm> |
| #include <cassert> |
| #include <utility> |
| |
| 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<ValueEntry> &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<ConstantInt>(V) && "No ConstantInt"); |
| OrigVal = V; |
| Instruction *I = dyn_cast<Instruction>(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::getZero(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<Instruction>(V); |
| if (I && I->hasOneUse() && I->getOpcode() == Opcode) |
| if (!isa<FPMathOperator>(I) || I->isFast()) |
| return cast<BinaryOperator>(I); |
| return nullptr; |
| } |
| |
| static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1, |
| unsigned Opcode2) { |
| auto *I = dyn_cast<Instruction>(V); |
| if (I && I->hasOneUse() && |
| (I->getOpcode() == Opcode1 || I->getOpcode() == Opcode2)) |
| if (!isa<FPMathOperator>(I) || I->isFast()) |
| return cast<BinaryOperator>(I); |
| return nullptr; |
| } |
| |
| void ReassociatePass::BuildRankMap(Function &F, |
| ReversePostOrderTraversal<Function*> &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<Instruction>(V); |
| if (!I) { |
| if (isa<Argument>(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<BinaryOperator>(I) && "Expected binary operator."); |
| assert(I->isCommutative() && "Expected commutative operator."); |
| |
| Value *LHS = I->getOperand(0); |
| Value *RHS = I->getOperand(1); |
| if (LHS == RHS || isa<Constant>(RHS)) |
| return; |
| if (isa<Constant>(LHS) || getRank(RHS) < getRank(LHS)) |
| cast<BinaryOperator>(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<FPMathOperator>(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<FPMathOperator>(FlagsOp)->getFastMathFlags()); |
| return Res; |
| } |
| } |
| |
| static Instruction *CreateNeg(Value *S1, const Twine &Name, |
| Instruction *InsertBefore, Value *FlagsOp) { |
| if (S1->getType()->isIntOrIntVectorTy()) |
| return BinaryOperator::CreateNeg(S1, Name, InsertBefore); |
| |
| if (auto *FMFSource = dyn_cast<Instruction>(FlagsOp)) |
| return UnaryOperator::CreateFNegFMF(S1, FMFSource, Name, InsertBefore); |
| |
| return UnaryOperator::CreateFNeg(S1, Name, InsertBefore); |
| } |
| |
| /// Replace 0-X with X*-1. |
| static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) { |
| assert((isa<UnaryOperator>(Neg) || isa<BinaryOperator>(Neg)) && |
| "Expected a Negate!"); |
| // FIXME: It's not safe to lower a unary FNeg into a FMul by -1.0. |
| unsigned OpNo = isa<BinaryOperator>(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<Value*, APInt>; |
| |
| /// 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<RepeatedValue> &Ops) { |
| assert((isa<UnaryOperator>(I) || isa<BinaryOperator>(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<std::pair<Instruction*, APInt>, 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<Value *, APInt>; |
| LeafMap Leaves; // Leaf -> Total weight so far. |
| SmallVector<Value *, 8> LeafOrder; // Ensure deterministic leaf output order. |
| |
| #ifndef NDEBUG |
| SmallPtrSet<Value *, 8> Visited; // For checking the iteration scheme. |
| #endif |
| while (!Worklist.empty()) { |
| std::pair<Instruction*, APInt> 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<Instruction>(Op) || |
| cast<Instruction>(Op)->getOpcode() != Opcode |
| || (isa<FPMathOperator>(Op) && |
| !cast<Instruction>(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<Instruction>(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<ValueEntry> &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<BinaryOperator*, 8> 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<Value*, 8> 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<FPMathOperator>(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<BinaryOperator>(*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<Constant>(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<Instruction>(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<Instruction>(V)) { |
| if (InvokeInst *II = dyn_cast<InvokeInst>(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<PHINode>(InsertPt) || |
| InsertPt->isEHPad())) { |
| if (isa<CatchSwitchInst>(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. |
| Instruction *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI); |
| ToRedo.insert(NewNeg); |
| return NewNeg; |
| } |
| |
| // See if this `or` looks like an load widening reduction, i.e. that it |
| // consists of an `or`/`shl`/`zext`/`load` nodes only. Note that we don't |
| // ensure that the pattern is *really* a load widening reduction, |
| // we do not ensure that it can really be replaced with a widened load, |
| // only that it mostly looks like one. |
| static bool isLoadCombineCandidate(Instruction *Or) { |
| SmallVector<Instruction *, 8> Worklist; |
| SmallSet<Instruction *, 8> Visited; |
| |
| auto Enqueue = [&](Value *V) { |
| auto *I = dyn_cast<Instruction>(V); |
| // Each node of an `or` reduction must be an instruction, |
| if (!I) |
| return false; // Node is certainly not part of an `or` load reduction. |
| // Only process instructions we have never processed before. |
| if (Visited.insert(I).second) |
| Worklist.emplace_back(I); |
| return true; // Will need to look at parent nodes. |
| }; |
| |
| if (!Enqueue(Or)) |
| return false; // Not an `or` reduction pattern. |
| |
| while (!Worklist.empty()) { |
| auto *I = Worklist.pop_back_val(); |
| |
| // Okay, which instruction is this node? |
| switch (I->getOpcode()) { |
| case Instruction::Or: |
| // Got an `or` node. That's fine, just recurse into it's operands. |
| for (Value *Op : I->operands()) |
| if (!Enqueue(Op)) |
| return false; // Not an `or` reduction pattern. |
| continue; |
| |
| case Instruction::Shl: |
| case Instruction::ZExt: |
| // `shl`/`zext` nodes are fine, just recurse into their base operand. |
| if (!Enqueue(I->getOperand(0))) |
| return false; // Not an `or` reduction pattern. |
| continue; |
| |
| case Instruction::Load: |
| // Perfect, `load` node means we've reached an edge of the graph. |
| continue; |
| |
| default: // Unknown node. |
| return false; // Not an `or` reduction pattern. |
| } |
| } |
| |
| return true; |
| } |
| |
| /// Return true if it may be profitable to convert this (X|Y) into (X+Y). |
| static bool shouldConvertOrWithNoCommonBitsToAdd(Instruction *Or) { |
| // Don't bother to convert this up unless either the LHS is an associable add |
| // or subtract or mul or if this is only used by one of the above. |
| // This is only a compile-time improvement, it is not needed for correctness! |
| auto isInteresting = [](Value *V) { |
| for (auto Op : {Instruction::Add, Instruction::Sub, Instruction::Mul, |
| Instruction::Shl}) |
| if (isReassociableOp(V, Op)) |
| return true; |
| return false; |
| }; |
| |
| if (any_of(Or->operands(), isInteresting)) |
| return true; |
| |
| Value *VB = Or->user_back(); |
| if (Or->hasOneUse() && isInteresting(VB)) |
| return true; |
| |
| return false; |
| } |
| |
| /// If we have (X|Y), and iff X and Y have no common bits set, |
| /// transform this into (X+Y) to allow arithmetics reassociation. |
| static BinaryOperator *convertOrWithNoCommonBitsToAdd(Instruction *Or) { |
| // Convert an or into an add. |
| BinaryOperator *New = |
| CreateAdd(Or->getOperand(0), Or->getOperand(1), "", Or, Or); |
| New->setHasNoSignedWrap(); |
| New->setHasNoUnsignedWrap(); |
| New->takeName(Or); |
| |
| // Everyone now refers to the add instruction. |
| Or->replaceAllUsesWith(New); |
| New->setDebugLoc(Or->getDebugLoc()); |
| |
| LLVM_DEBUG(dbgs() << "Converted or into an add: " << *New << '\n'); |
| return New; |
| } |
| |
| /// 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<UndefValue>(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); |
| auto *SA = cast<ConstantInt>(Shl->getOperand(1)); |
| MulCst = ConstantExpr::getShl(MulCst, SA); |
| |
| 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. It can be preserved as long as we're not left shifting by |
| // bitwidth - 1. |
| bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap(); |
| bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap(); |
| unsigned BitWidth = Shl->getType()->getIntegerBitWidth(); |
| if (NSW && (NUW || SA->getValue().ult(BitWidth - 1))) |
| 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<ValueEntry> &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<Instruction>(Ops[j].Op)) |
| if (Instruction *I2 = dyn_cast<Instruction>(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<Instruction>(Ops[j].Op)) |
| if (Instruction *I2 = dyn_cast<Instruction>(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<WeakTrackingVH> &Ops) { |
| if (Ops.size() == 1) return Ops.back(); |
| |
| Value *V1 = Ops.pop_back_val(); |
| 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<RepeatedValue, 8> Tree; |
| MadeChange |= LinearizeExprTree(BO, Tree); |
| SmallVector<ValueEntry, 8> 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<ConstantInt>(Factor)) { |
| if (ConstantInt *FC2 = dyn_cast<ConstantInt>(Factors[i].Op)) |
| if (FC1->getValue() == -FC2->getValue()) { |
| FoundFactor = NeedsNegate = true; |
| Factors.erase(Factors.begin()+i); |
| break; |
| } |
| } else if (ConstantFP *FC1 = dyn_cast<ConstantFP>(Factor)) { |
| if (ConstantFP *FC2 = dyn_cast<ConstantFP>(Factors[i].Op)) { |
| const APFloat &F1 = FC1->getValueAPF(); |
| APFloat F2(FC2->getValueAPF()); |
| F2.changeSign(); |
| if (F1 == F2) { |
| 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<Value*> &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<ValueEntry> &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.isZero()) |
| return nullptr; |
| |
| if (ConstOpnd.isAllOnes()) |
| 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().isZero()) |
| 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<Instruction>(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.isZero() && !C3.isAllOnes()) { |
| 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.isZero() && !C3.isAllOnes()) { |
| 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<Instruction>(Opnd1->getValue())) |
| RedoInsts.insert(T); |
| if (Instruction *T = dyn_cast<Instruction>(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<ValueEntry> &Ops) { |
| if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops)) |
| return V; |
| |
| if (Ops.size() == 1) |
| return nullptr; |
| |
| SmallVector<XorOpnd, 8> Opnds; |
| SmallVector<XorOpnd*, 8> 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.isZero() && 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.isZero()) { |
| 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.isZero()); |
| 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<ValueEntry> &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<Value*, unsigned> 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<Value*, 8> Factors; |
| FindSingleUseMultiplyFactors(BOp, Factors); |
| assert(Factors.size() > 1 && "Bad linearize!"); |
| |
| // Add one to FactorOccurrences for each unique factor in this op. |
| SmallPtrSet<Value*, 8> 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<ConstantInt>(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<ConstantFP>(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<WeakTrackingVH, 4> 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<Instruction>(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<ValueEntry> &Ops, |
| SmallVectorImpl<Factor> &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(IRBuilderBase &Builder, |
| SmallVectorImpl<Value*> &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(IRBuilderBase &Builder, |
| SmallVectorImpl<Factor> &Factors) { |
| assert(Factors[0].Power); |
| SmallVector<Value *, 4> 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<Value *, 4> 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<Instruction>(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<ValueEntry> &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<Factor, 4> 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<FPMathOperator>(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<ValueEntry> &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<Constant>(Ops.back().Op)) { |
| Constant *C = cast<Constant>(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<Value *, 4> Ops(I->operands()); |
| ValueRankMap.erase(I); |
| Insts.remove(I); |
| RedoInsts.remove(I); |
| llvm::salvageDebugInfo(*I); |
| I->eraseFromParent(); |
| for (auto Op : Ops) |
| if (Instruction *OpInst = dyn_cast<Instruction>(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<Value *, 8> Ops(I->operands()); |
| // Erase the dead instruction. |
| ValueRankMap.erase(I); |
| RedoInsts.remove(I); |
| llvm::salvageDebugInfo(*I); |
| I->eraseFromParent(); |
| // Optimize its operands. |
| SmallPtrSet<Instruction *, 8> Visited; // Detect self-referential nodes. |
| for (unsigned i = 0, e = Ops.size(); i != e; ++i) |
| if (Instruction *Op = dyn_cast<Instruction>(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<Instruction *> &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<Instruction *, 4> 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<Instruction>(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<UnaryOperator>(I) && !isa<BinaryOperator>(I)) |
| return; |
| |
| if (I->getOpcode() == Instruction::Shl && isa<ConstantInt>(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 bitwise or instruction of operands |
| // with no common bits set, convert it to X+Y. |
| if (I->getOpcode() == Instruction::Or && |
| shouldConvertOrWithNoCommonBitsToAdd(I) && !isLoadCombineCandidate(I) && |
| haveNoCommonBitsSet(I->getOperand(0), I->getOperand(1), |
| I->getModule()->getDataLayout(), /*AC=*/nullptr, I, |
| /*DT=*/nullptr)) { |
| Instruction *NI = convertOrWithNoCommonBitsToAdd(I); |
| RedoInsts.insert(I); |
| MadeChange = true; |
| I = NI; |
| } |
| |
| // 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<BinaryOperator>(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<BinaryOperator>(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<BinaryOperator>(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<BinaryOperator>(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<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub) |
| return; |
| if (BO->hasOneUse() && BO->getOpcode() == Instruction::FAdd && |
| cast<Instruction>(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<RepeatedValue, 8> Tree; |
| MadeChange |= LinearizeExprTree(I, Tree); |
| SmallVector<ValueEntry, 8> Ops; |
| Ops.reserve(Tree.size()); |
| for (const RepeatedValue &E : Tree) |
| 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<Instruction>(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<Instruction>(I->user_back())->getOpcode() == Instruction::Add && |
| isa<ConstantInt>(Ops.back().Op) && |
| cast<ConstantInt>(Ops.back().Op)->isMinusOne()) { |
| ValueEntry Tmp = Ops.pop_back_val(); |
| Ops.insert(Ops.begin(), Tmp); |
| } else if (I->getOpcode() == Instruction::FMul && |
| cast<Instruction>(I->user_back())->getOpcode() == |
| Instruction::FAdd && |
| isa<ConstantFP>(Ops.back().Op) && |
| cast<ConstantFP>(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<Instruction>(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<unsigned, unsigned> 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<Value *>()(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<Function *> &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<Value *, 8> Worklist = { I.getOperand(0), I.getOperand(1) }; |
| SmallVector<Value *, 8> Ops; |
| while (!Worklist.empty() && Ops.size() <= GlobalReassociateLimit) { |
| Value *Op = Worklist.pop_back_val(); |
| Instruction *OpI = dyn_cast<Instruction>(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<std::pair<Value *, Value*>, 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<Value *>()(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<Function *> 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<CFGAnalyses>(); |
| 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<AAResultsWrapperPass>(); |
| AU.addPreserved<BasicAAWrapperPass>(); |
| AU.addPreserved<GlobalsAAWrapperPass>(); |
| } |
| }; |
| |
| } // 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(); |
| } |