[llvm] 1984a27 - [DBG][OPT] Attempt to salvage or undef debug info when removing trivially deletable instructions in the Reassociate Expression pass.
Tom Weaver via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 11 06:02:54 PST 2019
Author: Tom Weaver
Date: 2019-11-11T13:47:13Z
New Revision: 1984a27db58e9053371ab6d6dc288c81c8a071ac
URL: https://github.com/llvm/llvm-project/commit/1984a27db58e9053371ab6d6dc288c81c8a071ac
DIFF: https://github.com/llvm/llvm-project/commit/1984a27db58e9053371ab6d6dc288c81c8a071ac.diff
LOG: [DBG][OPT] Attempt to salvage or undef debug info when removing trivially deletable instructions in the Reassociate Expression pass.
Reviewed By: aprantl, vsk
Differential revision: https://reviews.llvm.org/D69943
Added:
llvm/lib/Transforms/Scalar/Reassociate.cpp.rej
llvm/test/Transforms/Reassociate/reassociate_salvages_debug_info.ll
llvm/test/Transforms/Reassociate/undef_intrinsics_when_deleting_instructions.ll
Modified:
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp.rej b/llvm/lib/Transforms/Scalar/Reassociate.cpp.rej
new file mode 100644
index 000000000000..83c547675403
--- /dev/null
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp.rej
@@ -0,0 +1,2506 @@
+--- llvm/lib/Transforms/Scalar/Reassociate.cpp
++++ llvm/lib/Transforms/Scalar/Reassociate.cpp
+@@ -1,2501 +1,2503 @@
+ //===- Reassociate.cpp - Reassociate binary expressions -------------------===//
+ //
+ // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+ // See https://llvm.org/LICENSE.txt for license information.
+ // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ //
+ //===----------------------------------------------------------------------===//
+ //
+ // This pass reassociates commutative expressions in an order that is designed
+ // to promote better constant propagation, GCSE, LICM, PRE, etc.
+ //
+ // For example: 4 + (x + 5) -> x + (4 + 5)
+ //
+ // In the implementation of this algorithm, constants are assigned rank = 0,
+ // function arguments are rank = 1, and other values are assigned ranks
+ // corresponding to the reverse post order traversal of current function
+ // (starting at 2), which effectively gives values in deep loops higher rank
+ // than values not in loops.
+ //
+ //===----------------------------------------------------------------------===//
+
+ #include "llvm/Transforms/Scalar/Reassociate.h"
+ #include "llvm/ADT/APFloat.h"
+ #include "llvm/ADT/APInt.h"
+ #include "llvm/ADT/DenseMap.h"
+ #include "llvm/ADT/PostOrderIterator.h"
+ #include "llvm/ADT/SetVector.h"
+ #include "llvm/ADT/SmallPtrSet.h"
+ #include "llvm/ADT/SmallSet.h"
+ #include "llvm/ADT/SmallVector.h"
+ #include "llvm/ADT/Statistic.h"
+ #include "llvm/Analysis/GlobalsModRef.h"
+ #include "llvm/Transforms/Utils/Local.h"
+ #include "llvm/Analysis/ValueTracking.h"
+ #include "llvm/IR/Argument.h"
+ #include "llvm/IR/BasicBlock.h"
+ #include "llvm/IR/CFG.h"
+ #include "llvm/IR/Constant.h"
+ #include "llvm/IR/Constants.h"
+ #include "llvm/IR/Function.h"
+ #include "llvm/IR/IRBuilder.h"
+ #include "llvm/IR/InstrTypes.h"
+ #include "llvm/IR/Instruction.h"
+ #include "llvm/IR/Instructions.h"
+ #include "llvm/IR/IntrinsicInst.h"
+ #include "llvm/IR/Operator.h"
+ #include "llvm/IR/PassManager.h"
+ #include "llvm/IR/PatternMatch.h"
+ #include "llvm/IR/Type.h"
+ #include "llvm/IR/User.h"
+ #include "llvm/IR/Value.h"
+ #include "llvm/IR/ValueHandle.h"
+ #include "llvm/Pass.h"
+ #include "llvm/Support/Casting.h"
+ #include "llvm/Support/Debug.h"
+ #include "llvm/Support/ErrorHandling.h"
+ #include "llvm/Support/raw_ostream.h"
+ #include "llvm/Transforms/Scalar.h"
+ #include <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::getNullValue(V->getType()->getScalarSizeInBits());
+ isOr = true;
+ }
+
+ /// Return true if V is an instruction of the specified opcode and if it
+ /// only has one use.
+ static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
+ auto *I = dyn_cast<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
diff erent 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 BinaryOperator *CreateNeg(Value *S1, const Twine &Name,
+ Instruction *InsertBefore, Value *FlagsOp) {
+ if (S1->getType()->isIntOrIntVectorTy())
+ return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
+ else {
+ BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore);
+ Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
+ return Res;
+ }
+ }
+
+ /// 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
diff erent. 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
diff erent
+ /// 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 sanity 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
diff erent 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
diff ers 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
diff ers 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.
+ BinaryOperator *NewNeg = CreateNeg(V, V->getName() + ".neg", BI, BI);
+ ToRedo.insert(NewNeg);
+ return NewNeg;
+ }
+
+ /// Return true if we should break up this subtract of X-Y into (X + -Y).
+ static bool ShouldBreakUpSubtract(Instruction *Sub) {
+ // If this is a negation, we can't split it up!
+ if (match(Sub, m_Neg(m_Value())) || match(Sub, m_FNeg(m_Value())))
+ return false;
+
+ // Don't breakup X - undef.
+ if (isa<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);
+ MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
+
+ BinaryOperator *Mul =
+ BinaryOperator::CreateMul(Shl->getOperand(0), MulCst, "", Shl);
+ Shl->setOperand(0, UndefValue::get(Shl->getType())); // Drop use of op.
+ Mul->takeName(Shl);
+
+ // Everyone now refers to the mul instruction.
+ Shl->replaceAllUsesWith(Mul);
+ Mul->setDebugLoc(Shl->getDebugLoc());
+
+ // We can safely preserve the nuw flag in all cases. It's also safe to turn a
+ // nuw nsw shl into a nuw nsw mul. However, nsw in isolation requires special
+ // handling.
+ bool NSW = cast<BinaryOperator>(Shl)->hasNoSignedWrap();
+ bool NUW = cast<BinaryOperator>(Shl)->hasNoUnsignedWrap();
+ if (NSW && NUW)
+ Mul->setHasNoSignedWrap(true);
+ Mul->setHasNoUnsignedWrap(NUW);
+ return Mul;
+ }
+
+ /// Scan backwards and forwards among values with the same rank as element i
+ /// to see if X exists. If X does not exist, return i. This is useful when
+ /// scanning for 'x' when we see '-x' because they both get the same rank.
+ static unsigned FindInOperandList(const SmallVectorImpl<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.back();
+ Ops.pop_back();
+ Value *V2 = EmitAddTreeOfValues(I, Ops);
+ return CreateAdd(V2, V1, "reass.add", I, I);
+ }
+
+ /// If V is an expression tree that is a multiplication sequence,
+ /// and if this sequence contains a multiply by Factor,
+ /// remove Factor from the tree and return the new tree.
+ Value *ReassociatePass::RemoveFactorFromExpression(Value *V, Value *Factor) {
+ BinaryOperator *BO = isReassociableOp(V, Instruction::Mul, Instruction::FMul);
+ if (!BO)
+ return nullptr;
+
+ SmallVector<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.compare(F2) == APFloat::cmpEqual) {
+ FoundFactor = NeedsNegate = true;
+ Factors.erase(Factors.begin() + i);
+ break;
+ }
+ }
+ }
+ }
+
+ if (!FoundFactor) {
+ // Make sure to restore the operands to the expression tree.
+ RewriteExprTree(BO, Factors);
+ return nullptr;
+ }
+
+ BasicBlock::iterator InsertPt = ++BO->getIterator();
+
+ // If this was just a single multiply, remove the multiply and return the only
+ // remaining operand.
+ if (Factors.size() == 1) {
+ RedoInsts.insert(BO);
+ V = Factors[0].Op;
+ } else {
+ RewriteExprTree(BO, Factors);
+ V = BO;
+ }
+
+ if (NeedsNegate)
+ V = CreateNeg(V, "neg", &*InsertPt, BO);
+
+ return V;
+ }
+
+ /// If V is a single-use multiply, recursively add its operands as factors,
+ /// otherwise add V to the list of factors.
+ ///
+ /// Ops is the top-level list of add operands we're trying to factor.
+ static void FindSingleUseMultiplyFactors(Value *V,
+ SmallVectorImpl<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.isNullValue())
+ return nullptr;
+
+ if (ConstOpnd.isAllOnesValue())
+ return Opnd;
+
+ Instruction *I = BinaryOperator::CreateAnd(
+ Opnd, ConstantInt::get(Opnd->getType(), ConstOpnd), "and.ra",
+ InsertBefore);
+ I->setDebugLoc(InsertBefore->getDebugLoc());
+ return I;
+ }
+
+ // Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
+ // into "R ^ C", where C would be 0, and R is a symbolic value.
+ //
+ // If it was successful, true is returned, and the "R" and "C" is returned
+ // via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
+ // and both "Res" and "ConstOpnd" remain unchanged.
+ bool ReassociatePass::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
+ APInt &ConstOpnd, Value *&Res) {
+ // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
+ // = ((x | c1) ^ c1) ^ (c1 ^ c2)
+ // = (x & ~c1) ^ (c1 ^ c2)
+ // It is useful only when c1 == c2.
+ if (!Opnd1->isOrExpr() || Opnd1->getConstPart().isNullValue())
+ return false;
+
+ if (!Opnd1->getValue()->hasOneUse())
+ return false;
+
+ const APInt &C1 = Opnd1->getConstPart();
+ if (C1 != ConstOpnd)
+ return false;
+
+ Value *X = Opnd1->getSymbolicPart();
+ Res = createAndInstr(I, X, ~C1);
+ // ConstOpnd was C2, now C1 ^ C2.
+ ConstOpnd ^= C1;
+
+ if (Instruction *T = dyn_cast<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.isNullValue() && !C3.isAllOnesValue()) {
+ int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
+ if (NewInstNum > DeadInstNum)
+ return false;
+ }
+
+ Res = createAndInstr(I, X, C3);
+ ConstOpnd ^= C1;
+ } else if (Opnd1->isOrExpr()) {
+ // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
+ //
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3 = C1 ^ C2;
+
+ // Do not increase code size
+ if (!C3.isNullValue() && !C3.isAllOnesValue()) {
+ int NewInstNum = ConstOpnd.getBoolValue() ? 1 : 2;
+ if (NewInstNum > DeadInstNum)
+ return false;
+ }
+
+ Res = createAndInstr(I, X, C3);
+ ConstOpnd ^= C3;
+ } else {
+ // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
+ //
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3 = C1 ^ C2;
+ Res = createAndInstr(I, X, C3);
+ }
+
+ // Put the original operands in the Redo list; hope they will be deleted
+ // as dead code.
+ if (Instruction *T = dyn_cast<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.isNullValue() &&
+ CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
+ Changed = true;
+ if (CV)
+ *CurrOpnd = XorOpnd(CV);
+ else {
+ CurrOpnd->Invalidate();
+ continue;
+ }
+ }
+
+ if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
+ PrevOpnd = CurrOpnd;
+ continue;
+ }
+
+ // step 3.2: When previous and current operands share the same symbolic
+ // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
+ if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
+ // Remove previous operand
+ PrevOpnd->Invalidate();
+ if (CV) {
+ *CurrOpnd = XorOpnd(CV);
+ PrevOpnd = CurrOpnd;
+ } else {
+ CurrOpnd->Invalidate();
+ PrevOpnd = nullptr;
+ }
+ Changed = true;
+ }
+ }
+
+ // Step 4: Reassemble the Ops
+ if (Changed) {
+ Ops.clear();
+ for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
+ XorOpnd &O = Opnds[i];
+ if (O.isInvalid())
+ continue;
+ ValueEntry VE(getRank(O.getValue()), O.getValue());
+ Ops.push_back(VE);
+ }
+ if (!ConstOpnd.isNullValue()) {
+ Value *C = ConstantInt::get(Ty, ConstOpnd);
+ ValueEntry VE(getRank(C), C);
+ Ops.push_back(VE);
+ }
+ unsigned Sz = Ops.size();
+ if (Sz == 1)
+ return Ops.back().Op;
+ if (Sz == 0) {
+ assert(ConstOpnd.isNullValue());
+ return ConstantInt::get(Ty, ConstOpnd);
+ }
+ }
+
+ return nullptr;
+ }
+
+ /// Optimize a series of operands to an 'add' instruction. This
+ /// optimizes based on identities. If it can be reduced to a single Value, it
+ /// is returned, otherwise the Ops list is mutated as necessary.
+ Value *ReassociatePass::OptimizeAdd(Instruction *I,
+ SmallVectorImpl<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
diff erently.
+ 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(IRBuilder<> &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(IRBuilder<> &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->op_begin(), I->op_end());
+ ValueRankMap.erase(I);
+ Insts.remove(I);
+ RedoInsts.remove(I);
++ llvm::salvageDebugInfoOrMarkUndef(*I);
+ I->eraseFromParent();
+ for (auto Op : Ops)
+ if (Instruction *OpInst = dyn_cast<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->op_begin(), I->op_end());
+ // Erase the dead instruction.
+ ValueRankMap.erase(I);
+ RedoInsts.remove(I);
++ llvm::salvageDebugInfoOrMarkUndef(*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 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 (unsigned i = 0, e = Tree.size(); i != e; ++i) {
+ RepeatedValue E = Tree[i];
+ Ops.append(E.second.getZExtValue(),
+ ValueEntry(getRank(E.first), E.first));
+ }
+
+ LLVM_DEBUG(dbgs() << "RAIn:\t"; PrintOps(I, Ops); dbgs() << '\n');
+
+ // Now that we have linearized the tree to a list and have gathered all of
+ // the operands and their ranks, sort the operands by their rank. Use a
+ // stable_sort so that values with equal ranks will have their relative
+ // positions maintained (and so the compiler is deterministic). Note that
+ // this sorts so that the highest ranking values end up at the beginning of
+ // the vector.
+ llvm::stable_sort(Ops);
+
+ // Now that we have the expression tree in a convenient
+ // sorted form, optimize it globally if possible.
+ if (Value *V = OptimizeExpression(I, Ops)) {
+ if (V == I)
+ // Self-referential expression in unreachable code.
+ return;
+ // This expression tree simplified to something that isn't a tree,
+ // eliminate it.
+ LLVM_DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
+ I->replaceAllUsesWith(V);
+ if (Instruction *VI = dyn_cast<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
diff erent 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>();
+ PA.preserve<GlobalsAA>();
+ 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<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();
+ }
diff --git a/llvm/test/Transforms/Reassociate/reassociate_salvages_debug_info.ll b/llvm/test/Transforms/Reassociate/reassociate_salvages_debug_info.ll
new file mode 100644
index 000000000000..34e0b9a04bb3
--- /dev/null
+++ b/llvm/test/Transforms/Reassociate/reassociate_salvages_debug_info.ll
@@ -0,0 +1,50 @@
+; RUN: opt < %s -reassociate -S | FileCheck %s
+
+; Check that reassociate pass now salvages debug info when dropping instructions.
+
+define hidden i32 @main(i32 %argc, i8** %argv) {
+entry:
+ ; CHECK: call void @llvm.dbg.value(metadata i32 %argc, metadata [[VAR_B:![0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 1, DW_OP_stack_value))
+ %add = add nsw i32 %argc, 1, !dbg !26
+ call void @llvm.dbg.value(metadata i32 %add, metadata !22, metadata !DIExpression()), !dbg !25
+ %add1 = add nsw i32 %argc, %add, !dbg !27
+ ret i32 %add1, !dbg !28
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, debugInfoForProfiling: true, nameTableKind: None)
+!1 = !DIFile(filename: "test2.cpp", directory: "C:\")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 10.0.0"}
+!8 = distinct !DISubprogram(name: "main", scope: !9, file: !9, line: 1, type: !10, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !18)
+!9 = !DIFile(filename: "./test2.cpp", directory: "C:\")
+!10 = !DISubroutineType(types: !11)
+!11 = !{!12, !13, !14}
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !12)
+!14 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !15, size: 64)
+!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64)
+!16 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !17)
+!17 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
+!18 = !{!19, !20, !21, !22, !23, !24}
+!19 = !DILocalVariable(name: "argc", arg: 1, scope: !8, file: !9, line: 1, type: !13)
+!20 = !DILocalVariable(name: "argv", arg: 2, scope: !8, file: !9, line: 1, type: !14)
+!21 = !DILocalVariable(name: "a", scope: !8, file: !9, line: 2, type: !12)
+; CHECK: [[VAR_B]] = !DILocalVariable(name: "b"
+!22 = !DILocalVariable(name: "b", scope: !8, file: !9, line: 3, type: !12)
+!23 = !DILocalVariable(name: "to_return", scope: !8, file: !9, line: 4, type: !12)
+!24 = !DILocalVariable(name: "result", scope: !8, file: !9, line: 5, type: !12)
+!25 = !DILocation(line: 0, scope: !8)
+!26 = !DILocation(line: 3, scope: !8)
+!27 = !DILocation(line: 4, scope: !8)
+!28 = !DILocation(line: 6, scope: !8)
diff --git a/llvm/test/Transforms/Reassociate/undef_intrinsics_when_deleting_instructions.ll b/llvm/test/Transforms/Reassociate/undef_intrinsics_when_deleting_instructions.ll
new file mode 100644
index 000000000000..98c51c5cf8bb
--- /dev/null
+++ b/llvm/test/Transforms/Reassociate/undef_intrinsics_when_deleting_instructions.ll
@@ -0,0 +1,95 @@
+; RUN: opt < %s -reassociate -S | FileCheck %s
+
+; Check that reassociate pass now undefs debug intrinsics that reference a value
+; that gets dropped and cannot be salvaged.
+
+define hidden i32 @main() local_unnamed_addr {
+entry:
+ %foo = alloca i32, align 4, !dbg !20
+ %foo.0.foo.0..sroa_cast = bitcast i32* %foo to i8*, !dbg !20
+ call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %foo.0.foo.0..sroa_cast), !dbg !20
+ store volatile i32 4, i32* %foo, align 4, !dbg !20, !tbaa !21
+ %foo.0.foo.0. = load volatile i32, i32* %foo, align 4, !dbg !25, !tbaa !21
+ %foo.0.foo.0.15 = load volatile i32, i32* %foo, align 4, !dbg !27, !tbaa !21
+ %foo.0.foo.0.16 = load volatile i32, i32* %foo, align 4, !dbg !28, !tbaa !21
+ ; CHECK-NOT: %add = add nsw i32 %foo.0.foo.0., %foo.0.foo.0.15
+ %add = add nsw i32 %foo.0.foo.0., %foo.0.foo.0.15, !dbg !29
+ ; CHECK: call void @llvm.dbg.value(metadata i32 undef, metadata [[VAR_A:![0-9]+]], metadata !DIExpression())
+ call void @llvm.dbg.value(metadata i32 %add, metadata !19, metadata !DIExpression()), !dbg !26
+ %foo.0.foo.0.17 = load volatile i32, i32* %foo, align 4, !dbg !30, !tbaa !21
+ %cmp = icmp eq i32 %foo.0.foo.0.17, 4, !dbg !30
+ br i1 %cmp, label %if.then, label %if.end, !dbg !32
+
+ ; CHECK-LABEL: if.then:
+if.then:
+ ; CHECK-NOT: %add1 = add nsw i32 %add, %foo.0.foo.0.16
+ %add1 = add nsw i32 %add, %foo.0.foo.0.16, !dbg !33
+ ; CHECK: call void @llvm.dbg.value(metadata i32 undef, metadata [[VAR_A]], metadata !DIExpression())
+ call void @llvm.dbg.value(metadata i32 %add1, metadata !19, metadata !DIExpression()), !dbg !26
+ ; CHECK: call void @llvm.dbg.value(metadata i32 undef, metadata [[VAR_CHEESE:![0-9]+]], metadata !DIExpression())
+ call void @llvm.dbg.value(metadata i32 %add, metadata !18, metadata !DIExpression()), !dbg !26
+ %sub = add nsw i32 %add, -12, !dbg !34
+ %sub3 = sub nsw i32 %add1, %sub, !dbg !34
+ %mul = mul nsw i32 %sub3, 20, !dbg !36
+ %div = sdiv i32 %mul, 3, !dbg !37
+ br label %if.end, !dbg !38
+
+if.end:
+ %a.0 = phi i32 [ %div, %if.then ], [ 0, %entry ], !dbg !39
+ call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %foo.0.foo.0..sroa_cast), !dbg !40
+ ret i32 %a.0, !dbg !41
+}
+
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #1
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #2
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #1
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, debugInfoForProfiling: true, nameTableKind: None)
+!1 = !DIFile(filename: "test.cpp", directory: "F:\")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!7 = !{!"clang version 10.0.0"}
+!8 = distinct !DISubprogram(name: "main", scope: !9, file: !9, line: 1, type: !10, scopeLine: 1, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !13)
+!9 = !DIFile(filename: "./test.cpp", directory: "F:\")
+!10 = !DISubroutineType(types: !11)
+!11 = !{!12}
+!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!13 = !{!14, !16, !17, !18, !19}
+!14 = !DILocalVariable(name: "foo", scope: !8, file: !9, line: 2, type: !15)
+!15 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !12)
+!16 = !DILocalVariable(name: "read1", scope: !8, file: !9, line: 3, type: !12)
+!17 = !DILocalVariable(name: "read2", scope: !8, file: !9, line: 4, type: !12)
+; CHECK: [[VAR_CHEESE]] = !DILocalVariable(name: "cheese"
+!18 = !DILocalVariable(name: "cheese", scope: !8, file: !9, line: 6, type: !12)
+; CHECK: [[VAR_A]] = !DILocalVariable(name: "a"
+!19 = !DILocalVariable(name: "a", scope: !8, file: !9, line: 7, type: !12)
+!20 = !DILocation(line: 2, scope: !8)
+!21 = !{!22, !22, i64 0}
+!22 = !{!"int", !23, i64 0}
+!23 = !{!"omnipotent char", !24, i64 0}
+!24 = !{!"Simple C++ TBAA"}
+!25 = !DILocation(line: 3, scope: !8)
+!26 = !DILocation(line: 0, scope: !8)
+!27 = !DILocation(line: 4, scope: !8)
+!28 = !DILocation(line: 6, scope: !8)
+!29 = !DILocation(line: 7, scope: !8)
+!30 = !DILocation(line: 10, scope: !31)
+!31 = distinct !DILexicalBlock(scope: !8, file: !9, line: 10)
+!32 = !DILocation(line: 10, scope: !8)
+!33 = !DILocation(line: 8, scope: !8)
+!34 = !DILocation(line: 12, scope: !35)
+!35 = distinct !DILexicalBlock(scope: !31, file: !9, line: 10)
+!36 = !DILocation(line: 13, scope: !35)
+!37 = !DILocation(line: 14, scope: !35)
+!38 = !DILocation(line: 15, scope: !35)
+!39 = !DILocation(line: 0, scope: !31)
+!40 = !DILocation(line: 20, scope: !8)
+!41 = !DILocation(line: 19, scope: !8)
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