mirror of
https://github.com/c64scene-ar/llvm-6502.git
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0edc5e8391
This does not require -ffast-math, and it gives CSE/GVN more options to eliminate duplicate expressions in, e.g.: return ((x + 0.1234 * y) * (x - 0.1234 * y)); Differential Revision: http://reviews.llvm.org/D4904 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216169 91177308-0d34-0410-b5e6-96231b3b80d8
2204 lines
83 KiB
C++
2204 lines
83 KiB
C++
//===- Reassociate.cpp - Reassociate binary expressions -------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass reassociates commutative expressions in an order that is designed
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// to promote better constant propagation, GCSE, LICM, PRE, etc.
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//
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// For example: 4 + (x + 5) -> x + (4 + 5)
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//
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// In the implementation of this algorithm, constants are assigned rank = 0,
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// function arguments are rank = 1, and other values are assigned ranks
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// corresponding to the reverse post order traversal of current function
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// (starting at 2), which effectively gives values in deep loops higher rank
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// than values not in loops.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DerivedTypes.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <algorithm>
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using namespace llvm;
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#define DEBUG_TYPE "reassociate"
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STATISTIC(NumChanged, "Number of insts reassociated");
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STATISTIC(NumAnnihil, "Number of expr tree annihilated");
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STATISTIC(NumFactor , "Number of multiplies factored");
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namespace {
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struct ValueEntry {
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unsigned Rank;
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Value *Op;
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ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {}
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};
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inline bool operator<(const ValueEntry &LHS, const ValueEntry &RHS) {
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return LHS.Rank > RHS.Rank; // Sort so that highest rank goes to start.
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}
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}
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#ifndef NDEBUG
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/// PrintOps - Print out the expression identified in the Ops list.
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///
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static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
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Module *M = I->getParent()->getParent()->getParent();
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dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
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<< *Ops[0].Op->getType() << '\t';
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for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
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dbgs() << "[ ";
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Ops[i].Op->printAsOperand(dbgs(), false, M);
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dbgs() << ", #" << Ops[i].Rank << "] ";
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}
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}
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#endif
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namespace {
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/// \brief Utility class representing a base and exponent pair which form one
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/// factor of some product.
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struct Factor {
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Value *Base;
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unsigned Power;
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Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {}
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/// \brief Sort factors by their Base.
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struct BaseSorter {
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bool operator()(const Factor &LHS, const Factor &RHS) {
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return LHS.Base < RHS.Base;
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}
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};
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/// \brief Compare factors for equal bases.
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struct BaseEqual {
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bool operator()(const Factor &LHS, const Factor &RHS) {
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return LHS.Base == RHS.Base;
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}
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};
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/// \brief Sort factors in descending order by their power.
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struct PowerDescendingSorter {
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bool operator()(const Factor &LHS, const Factor &RHS) {
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return LHS.Power > RHS.Power;
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}
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};
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/// \brief Compare factors for equal powers.
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struct PowerEqual {
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bool operator()(const Factor &LHS, const Factor &RHS) {
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return LHS.Power == RHS.Power;
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}
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};
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};
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/// Utility class representing a non-constant Xor-operand. We classify
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/// non-constant Xor-Operands into two categories:
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/// C1) The operand is in the form "X & C", where C is a constant and C != ~0
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/// C2)
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/// C2.1) The operand is in the form of "X | C", where C is a non-zero
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/// constant.
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/// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
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/// operand as "E | 0"
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class XorOpnd {
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public:
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XorOpnd(Value *V);
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bool isInvalid() const { return SymbolicPart == nullptr; }
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bool isOrExpr() const { return isOr; }
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Value *getValue() const { return OrigVal; }
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Value *getSymbolicPart() const { return SymbolicPart; }
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unsigned getSymbolicRank() const { return SymbolicRank; }
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const APInt &getConstPart() const { return ConstPart; }
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void Invalidate() { SymbolicPart = OrigVal = nullptr; }
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void setSymbolicRank(unsigned R) { SymbolicRank = R; }
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// Sort the XorOpnd-Pointer in ascending order of symbolic-value-rank.
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// The purpose is twofold:
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// 1) Cluster together the operands sharing the same symbolic-value.
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// 2) Operand having smaller symbolic-value-rank is permuted earlier, which
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// could potentially shorten crital path, and expose more loop-invariants.
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// Note that values' rank are basically defined in RPO order (FIXME).
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// So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
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// than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
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// "z" in the order of X-Y-Z is better than any other orders.
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struct PtrSortFunctor {
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bool operator()(XorOpnd * const &LHS, XorOpnd * const &RHS) {
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return LHS->getSymbolicRank() < RHS->getSymbolicRank();
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}
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};
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private:
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Value *OrigVal;
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Value *SymbolicPart;
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APInt ConstPart;
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unsigned SymbolicRank;
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bool isOr;
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};
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}
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namespace {
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class Reassociate : public FunctionPass {
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DenseMap<BasicBlock*, unsigned> RankMap;
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DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
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SetVector<AssertingVH<Instruction> > RedoInsts;
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bool MadeChange;
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public:
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static char ID; // Pass identification, replacement for typeid
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Reassociate() : FunctionPass(ID) {
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initializeReassociatePass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesCFG();
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}
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private:
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void BuildRankMap(Function &F);
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unsigned getRank(Value *V);
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void ReassociateExpression(BinaryOperator *I);
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void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
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Value *OptimizeExpression(BinaryOperator *I,
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SmallVectorImpl<ValueEntry> &Ops);
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Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
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Value *OptimizeXor(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
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bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, APInt &ConstOpnd,
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Value *&Res);
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bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
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APInt &ConstOpnd, Value *&Res);
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bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
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SmallVectorImpl<Factor> &Factors);
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Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
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SmallVectorImpl<Factor> &Factors);
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Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
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Value *RemoveFactorFromExpression(Value *V, Value *Factor);
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void EraseInst(Instruction *I);
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void optimizeFAddNegExpr(ConstantFP *ConstOperand, Instruction *I,
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int OperandNr);
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void OptimizeInst(Instruction *I);
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};
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}
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XorOpnd::XorOpnd(Value *V) {
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assert(!isa<ConstantInt>(V) && "No ConstantInt");
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OrigVal = V;
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Instruction *I = dyn_cast<Instruction>(V);
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SymbolicRank = 0;
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if (I && (I->getOpcode() == Instruction::Or ||
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I->getOpcode() == Instruction::And)) {
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Value *V0 = I->getOperand(0);
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Value *V1 = I->getOperand(1);
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if (isa<ConstantInt>(V0))
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std::swap(V0, V1);
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if (ConstantInt *C = dyn_cast<ConstantInt>(V1)) {
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ConstPart = C->getValue();
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SymbolicPart = V0;
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isOr = (I->getOpcode() == Instruction::Or);
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return;
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}
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}
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// view the operand as "V | 0"
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SymbolicPart = V;
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ConstPart = APInt::getNullValue(V->getType()->getIntegerBitWidth());
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isOr = true;
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}
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char Reassociate::ID = 0;
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INITIALIZE_PASS(Reassociate, "reassociate",
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"Reassociate expressions", false, false)
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// Public interface to the Reassociate pass
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FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
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/// isReassociableOp - Return true if V is an instruction of the specified
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/// opcode and if it only has one use.
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static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
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if (V->hasOneUse() && isa<Instruction>(V) &&
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cast<Instruction>(V)->getOpcode() == Opcode)
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return cast<BinaryOperator>(V);
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return nullptr;
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}
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static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode1,
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unsigned Opcode2) {
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if (V->hasOneUse() && isa<Instruction>(V) &&
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(cast<Instruction>(V)->getOpcode() == Opcode1 ||
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cast<Instruction>(V)->getOpcode() == Opcode2))
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return cast<BinaryOperator>(V);
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return nullptr;
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}
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static bool isUnmovableInstruction(Instruction *I) {
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switch (I->getOpcode()) {
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case Instruction::PHI:
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case Instruction::LandingPad:
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case Instruction::Alloca:
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case Instruction::Load:
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case Instruction::Invoke:
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case Instruction::UDiv:
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case Instruction::SDiv:
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case Instruction::FDiv:
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case Instruction::URem:
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case Instruction::SRem:
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case Instruction::FRem:
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return true;
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case Instruction::Call:
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return !isa<DbgInfoIntrinsic>(I);
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default:
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return false;
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}
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}
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void Reassociate::BuildRankMap(Function &F) {
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unsigned i = 2;
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// Assign distinct ranks to function arguments
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for (Function::arg_iterator I = F.arg_begin(), E = F.arg_end(); I != E; ++I)
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ValueRankMap[&*I] = ++i;
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ReversePostOrderTraversal<Function*> RPOT(&F);
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for (ReversePostOrderTraversal<Function*>::rpo_iterator I = RPOT.begin(),
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E = RPOT.end(); I != E; ++I) {
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BasicBlock *BB = *I;
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unsigned BBRank = RankMap[BB] = ++i << 16;
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// Walk the basic block, adding precomputed ranks for any instructions that
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// we cannot move. This ensures that the ranks for these instructions are
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// all different in the block.
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
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if (isUnmovableInstruction(I))
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ValueRankMap[&*I] = ++BBRank;
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}
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}
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unsigned Reassociate::getRank(Value *V) {
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Instruction *I = dyn_cast<Instruction>(V);
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if (!I) {
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if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
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return 0; // Otherwise it's a global or constant, rank 0.
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}
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if (unsigned Rank = ValueRankMap[I])
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return Rank; // Rank already known?
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// If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
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// we can reassociate expressions for code motion! Since we do not recurse
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// for PHI nodes, we cannot have infinite recursion here, because there
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// cannot be loops in the value graph that do not go through PHI nodes.
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unsigned Rank = 0, MaxRank = RankMap[I->getParent()];
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for (unsigned i = 0, e = I->getNumOperands();
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i != e && Rank != MaxRank; ++i)
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Rank = std::max(Rank, getRank(I->getOperand(i)));
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// If this is a not or neg instruction, do not count it for rank. This
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// assures us that X and ~X will have the same rank.
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Type *Ty = V->getType();
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if ((!Ty->isIntegerTy() && !Ty->isFloatingPointTy()) ||
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(!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I) &&
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!BinaryOperator::isFNeg(I)))
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++Rank;
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//DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = "
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// << Rank << "\n");
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return ValueRankMap[I] = Rank;
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}
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static BinaryOperator *CreateAdd(Value *S1, Value *S2, const Twine &Name,
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Instruction *InsertBefore, Value *FlagsOp) {
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if (S1->getType()->isIntegerTy())
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return BinaryOperator::CreateAdd(S1, S2, Name, InsertBefore);
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else {
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BinaryOperator *Res =
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BinaryOperator::CreateFAdd(S1, S2, Name, InsertBefore);
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Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
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return Res;
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}
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}
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static BinaryOperator *CreateMul(Value *S1, Value *S2, const Twine &Name,
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Instruction *InsertBefore, Value *FlagsOp) {
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if (S1->getType()->isIntegerTy())
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return BinaryOperator::CreateMul(S1, S2, Name, InsertBefore);
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else {
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BinaryOperator *Res =
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BinaryOperator::CreateFMul(S1, S2, Name, InsertBefore);
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Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
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return Res;
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}
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}
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static BinaryOperator *CreateNeg(Value *S1, const Twine &Name,
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Instruction *InsertBefore, Value *FlagsOp) {
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if (S1->getType()->isIntegerTy())
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return BinaryOperator::CreateNeg(S1, Name, InsertBefore);
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else {
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BinaryOperator *Res = BinaryOperator::CreateFNeg(S1, Name, InsertBefore);
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Res->setFastMathFlags(cast<FPMathOperator>(FlagsOp)->getFastMathFlags());
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return Res;
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}
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}
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/// LowerNegateToMultiply - Replace 0-X with X*-1.
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///
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static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
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Type *Ty = Neg->getType();
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Constant *NegOne = Ty->isIntegerTy() ? ConstantInt::getAllOnesValue(Ty)
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: ConstantFP::get(Ty, -1.0);
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BinaryOperator *Res = CreateMul(Neg->getOperand(1), NegOne, "", Neg, Neg);
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Neg->setOperand(1, Constant::getNullValue(Ty)); // Drop use of op.
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Res->takeName(Neg);
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Neg->replaceAllUsesWith(Res);
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Res->setDebugLoc(Neg->getDebugLoc());
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return Res;
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}
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/// CarmichaelShift - Returns k such that lambda(2^Bitwidth) = 2^k, where lambda
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/// is the Carmichael function. This means that x^(2^k) === 1 mod 2^Bitwidth for
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/// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
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/// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
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/// even x in Bitwidth-bit arithmetic.
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static unsigned CarmichaelShift(unsigned Bitwidth) {
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if (Bitwidth < 3)
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return Bitwidth - 1;
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return Bitwidth - 2;
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}
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/// IncorporateWeight - Add the extra weight 'RHS' to the existing weight 'LHS',
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/// reducing the combined weight using any special properties of the operation.
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/// The existing weight LHS represents the computation X op X op ... op X where
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/// X occurs LHS times. The combined weight represents X op X op ... op X with
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/// X occurring LHS + RHS times. If op is "Xor" for example then the combined
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/// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
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/// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
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static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
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// If we were working with infinite precision arithmetic then the combined
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// weight would be LHS + RHS. But we are using finite precision arithmetic,
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// and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
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// for nilpotent operations and addition, but not for idempotent operations
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// and multiplication), so it is important to correctly reduce the combined
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// weight back into range if wrapping would be wrong.
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// If RHS is zero then the weight didn't change.
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if (RHS.isMinValue())
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return;
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// If LHS is zero then the combined weight is RHS.
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if (LHS.isMinValue()) {
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LHS = RHS;
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return;
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}
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// From this point on we know that neither LHS nor RHS is zero.
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if (Instruction::isIdempotent(Opcode)) {
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// Idempotent means X op X === X, so any non-zero weight is equivalent to a
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// weight of 1. Keeping weights at zero or one also means that wrapping is
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// not a problem.
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assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
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return; // Return a weight of 1.
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}
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if (Instruction::isNilpotent(Opcode)) {
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// Nilpotent means X op X === 0, so reduce weights modulo 2.
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assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
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LHS = 0; // 1 + 1 === 0 modulo 2.
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return;
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}
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if (Opcode == Instruction::Add || Opcode == Instruction::FAdd) {
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// TODO: Reduce the weight by exploiting nsw/nuw?
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LHS += RHS;
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return;
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}
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assert((Opcode == Instruction::Mul || Opcode == Instruction::FMul) &&
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"Unknown associative operation!");
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unsigned Bitwidth = LHS.getBitWidth();
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// If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
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// can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
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// bit number x, since either x is odd in which case x^CM = 1, or x is even in
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// which case both x^W and x^(W - CM) are zero. By subtracting off multiples
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// of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
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// which by a happy accident means that they can always be represented using
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// Bitwidth bits.
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// TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
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// the Carmichael number).
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if (Bitwidth > 3) {
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/// CM - The value of Carmichael's lambda function.
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APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
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// 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;
|
|
}
|
|
}
|
|
|
|
typedef std::pair<Value*, APInt> RepeatedValue;
|
|
|
|
/// LinearizeExprTree - Given an associative binary expression, return the leaf
|
|
/// nodes in Ops along with their weights (how many times the leaf occurs). The
|
|
/// original expression is the same as
|
|
/// (Ops[0].first op Ops[0].first op ... Ops[0].first) <- Ops[0].second times
|
|
/// op
|
|
/// (Ops[1].first op Ops[1].first op ... Ops[1].first) <- Ops[1].second times
|
|
/// op
|
|
/// ...
|
|
/// op
|
|
/// (Ops[N].first op Ops[N].first op ... Ops[N].first) <- Ops[N].second times
|
|
///
|
|
/// Note that the values Ops[0].first, ..., Ops[N].first are all distinct.
|
|
///
|
|
/// This routine may modify the function, in which case it returns 'true'. The
|
|
/// changes it makes may well be destructive, changing the value computed by 'I'
|
|
/// to something completely different. Thus if the routine returns 'true' then
|
|
/// you MUST either replace I with a new expression computed from the Ops array,
|
|
/// or use RewriteExprTree to put the values back in.
|
|
///
|
|
/// A leaf node is either not a binary operation of the same kind as the root
|
|
/// node 'I' (i.e. is not a binary operator at all, or is, but with a different
|
|
/// opcode), or is the same kind of binary operator but has a use which either
|
|
/// does not belong to the expression, or does belong to the expression but is
|
|
/// a leaf node. Every leaf node has at least one use that is a non-leaf node
|
|
/// of the expression, while for non-leaf nodes (except for the root 'I') every
|
|
/// use is a non-leaf node of the expression.
|
|
///
|
|
/// For example:
|
|
/// expression graph node names
|
|
///
|
|
/// + | I
|
|
/// / \ |
|
|
/// + + | A, B
|
|
/// / \ / \ |
|
|
/// * + * | C, D, E
|
|
/// / \ / \ / \ |
|
|
/// + * | F, G
|
|
///
|
|
/// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
|
|
/// that order) (C, 1), (E, 1), (F, 2), (G, 2).
|
|
///
|
|
/// The expression is maximal: if some instruction is a binary operator of the
|
|
/// same kind as 'I', and all of its uses are non-leaf nodes of the expression,
|
|
/// then the instruction also belongs to the expression, is not a leaf node of
|
|
/// it, and its operands also belong to the expression (but may be leaf nodes).
|
|
///
|
|
/// NOTE: This routine will set operands of non-leaf non-root nodes to undef in
|
|
/// order to ensure that every non-root node in the expression has *exactly one*
|
|
/// use by a non-leaf node of the expression. This destruction means that the
|
|
/// caller MUST either replace 'I' with a new expression or use something like
|
|
/// RewriteExprTree to put the values back in if the routine indicates that it
|
|
/// made a change by returning 'true'.
|
|
///
|
|
/// In the above example either the right operand of A or the left operand of B
|
|
/// will be replaced by undef. If it is B's operand then this gives:
|
|
///
|
|
/// + | I
|
|
/// / \ |
|
|
/// + + | A, B - operand of B replaced with undef
|
|
/// / \ \ |
|
|
/// * + * | C, D, E
|
|
/// / \ / \ / \ |
|
|
/// + * | F, G
|
|
///
|
|
/// Note that such undef operands can only be reached by passing through 'I'.
|
|
/// For example, if you visit operands recursively starting from a leaf node
|
|
/// then you will never see such an undef operand unless you get back to 'I',
|
|
/// which requires passing through a phi node.
|
|
///
|
|
/// Note that this routine may also mutate binary operators of the wrong type
|
|
/// that have all uses inside the expression (i.e. only used by non-leaf nodes
|
|
/// of the expression) if it can turn them into binary operators of the right
|
|
/// type and thus make the expression bigger.
|
|
|
|
static bool LinearizeExprTree(BinaryOperator *I,
|
|
SmallVectorImpl<RepeatedValue> &Ops) {
|
|
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<BinaryOperator*, APInt>, 8> Worklist; // (Op, Weight)
|
|
Worklist.push_back(std::make_pair(I, APInt(Bitwidth, 1)));
|
|
bool MadeChange = 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.
|
|
typedef DenseMap<Value*, APInt> LeafMap;
|
|
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<BinaryOperator*, APInt> P = Worklist.pop_back_val();
|
|
I = P.first; // We examine the operands of this binary operator.
|
|
|
|
for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
|
|
Value *Op = I->getOperand(OpIdx);
|
|
APInt Weight = P.second; // Number of paths to this operand.
|
|
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) && "Not first visit!");
|
|
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) && "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.
|
|
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 if (It != Leaves.end()) {
|
|
// Already in the leaf map.
|
|
assert(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()));
|
|
MadeChange = 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)) {
|
|
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) &&
|
|
"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 (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op))
|
|
if ((Opcode == Instruction::Mul && BinaryOperator::isNeg(BO)) ||
|
|
(Opcode == Instruction::FMul && BinaryOperator::isFNeg(BO))) {
|
|
DEBUG(dbgs() << "MORPH LEAF: " << *Op << " (" << Weight << ") TO ");
|
|
BO = LowerNegateToMultiply(BO);
|
|
DEBUG(dbgs() << *BO << '\n');
|
|
Worklist.push_back(std::make_pair(BO, Weight));
|
|
MadeChange = true;
|
|
continue;
|
|
}
|
|
|
|
// Failed to morph into an expression of the right type. This really is
|
|
// a leaf.
|
|
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.push_back(std::make_pair(Identity, APInt(Bitwidth, 1)));
|
|
}
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
// RewriteExprTree - Now that the operands for this expression tree are
|
|
// linearized and optimized, emit them in-order.
|
|
void Reassociate::RewriteExprTree(BinaryOperator *I,
|
|
SmallVectorImpl<ValueEntry> &Ops) {
|
|
assert(Ops.size() > 1 && "Single values should be used directly!");
|
|
|
|
// Since our optimizations should never increase the number of operations, the
|
|
// new expression can usually be written reusing the existing binary operators
|
|
// from the original expression tree, without creating any new instructions,
|
|
// though the rewritten expression may have a completely different topology.
|
|
// We take care to not change anything if the new expression will be the same
|
|
// as the original. If more than trivial changes (like commuting operands)
|
|
// were made then we are obliged to clear out any optional subclass data like
|
|
// nsw flags.
|
|
|
|
/// NodesToRewrite - Nodes from the original expression available for writing
|
|
/// the new expression into.
|
|
SmallVector<BinaryOperator*, 8> NodesToRewrite;
|
|
unsigned Opcode = I->getOpcode();
|
|
BinaryOperator *Op = I;
|
|
|
|
/// NotRewritable - The operands being written will be the leaves of the new
|
|
/// expression and must not be used as inner nodes (via NodesToRewrite) by
|
|
/// mistake. Inner nodes are always reassociable, and usually leaves are not
|
|
/// (if they were they would have been incorporated into the expression and so
|
|
/// would not be leaves), so most of the time there is no danger of this. But
|
|
/// in rare cases a leaf may become reassociable if an optimization kills uses
|
|
/// of it, or it may momentarily become reassociable during rewriting (below)
|
|
/// due it being removed as an operand of one of its uses. Ensure that misuse
|
|
/// of leaf nodes as inner nodes cannot occur by remembering all of the future
|
|
/// leaves and refusing to reuse any of them as inner nodes.
|
|
SmallPtrSet<Value*, 8> NotRewritable;
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i)
|
|
NotRewritable.insert(Ops[i].Op);
|
|
|
|
// ExpressionChanged - Non-null if the rewritten expression differs from the
|
|
// original in some non-trivial way, requiring the clearing of optional flags.
|
|
// Flags are cleared from the operator in ExpressionChanged up to I inclusive.
|
|
BinaryOperator *ExpressionChanged = nullptr;
|
|
for (unsigned i = 0; ; ++i) {
|
|
// The last operation (which comes earliest in the IR) is special as both
|
|
// operands will come from Ops, rather than just one with the other being
|
|
// a subexpression.
|
|
if (i+2 == Ops.size()) {
|
|
Value *NewLHS = Ops[i].Op;
|
|
Value *NewRHS = Ops[i+1].Op;
|
|
Value *OldLHS = Op->getOperand(0);
|
|
Value *OldRHS = Op->getOperand(1);
|
|
|
|
if (NewLHS == OldLHS && NewRHS == OldRHS)
|
|
// Nothing changed, leave it alone.
|
|
break;
|
|
|
|
if (NewLHS == OldRHS && NewRHS == OldLHS) {
|
|
// The order of the operands was reversed. Swap them.
|
|
DEBUG(dbgs() << "RA: " << *Op << '\n');
|
|
Op->swapOperands();
|
|
DEBUG(dbgs() << "TO: " << *Op << '\n');
|
|
MadeChange = true;
|
|
++NumChanged;
|
|
break;
|
|
}
|
|
|
|
// The new operation differs non-trivially from the original. Overwrite
|
|
// the old operands with the new ones.
|
|
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);
|
|
}
|
|
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)) {
|
|
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;
|
|
}
|
|
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()->isFloatingPointTy())
|
|
NewOp->setFastMathFlags(I->getFastMathFlags());
|
|
} else {
|
|
NewOp = NodesToRewrite.pop_back_val();
|
|
}
|
|
|
|
DEBUG(dbgs() << "RA: " << *Op << '\n');
|
|
Op->setOperand(0, NewOp);
|
|
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;
|
|
ExpressionChanged->moveBefore(I);
|
|
ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
|
|
} while (1);
|
|
|
|
// Throw away any left over nodes from the original expression.
|
|
for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
|
|
RedoInsts.insert(NodesToRewrite[i]);
|
|
}
|
|
|
|
/// NegateValue - 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.
|
|
static Value *NegateValue(Value *V, Instruction *BI) {
|
|
if (ConstantFP *C = dyn_cast<ConstantFP>(V))
|
|
return ConstantExpr::getFNeg(C);
|
|
if (Constant *C = dyn_cast<Constant>(V))
|
|
return 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));
|
|
I->setOperand(1, NegateValue(I->getOperand(1), BI));
|
|
|
|
// 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");
|
|
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 (!BinaryOperator::isNeg(U) && !BinaryOperator::isFNeg(U))
|
|
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.
|
|
BinaryOperator *TheNeg = cast<BinaryOperator>(U);
|
|
|
|
// Verify that the negate is in this function, V might be a constant expr.
|
|
if (TheNeg->getParent()->getParent() != BI->getParent()->getParent())
|
|
continue;
|
|
|
|
BasicBlock::iterator InsertPt;
|
|
if (Instruction *InstInput = dyn_cast<Instruction>(V)) {
|
|
if (InvokeInst *II = dyn_cast<InvokeInst>(InstInput)) {
|
|
InsertPt = II->getNormalDest()->begin();
|
|
} else {
|
|
InsertPt = InstInput;
|
|
++InsertPt;
|
|
}
|
|
while (isa<PHINode>(InsertPt)) ++InsertPt;
|
|
} else {
|
|
InsertPt = TheNeg->getParent()->getParent()->getEntryBlock().begin();
|
|
}
|
|
TheNeg->moveBefore(InsertPt);
|
|
return TheNeg;
|
|
}
|
|
|
|
// Insert a 'neg' instruction that subtracts the value from zero to get the
|
|
// negation.
|
|
return CreateNeg(V, V->getName() + ".neg", BI, BI);
|
|
}
|
|
|
|
/// ShouldBreakUpSubtract - 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 (BinaryOperator::isNeg(Sub) || BinaryOperator::isFNeg(Sub))
|
|
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;
|
|
}
|
|
|
|
/// BreakUpSubtract - 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) {
|
|
// 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);
|
|
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());
|
|
|
|
DEBUG(dbgs() << "Negated: " << *New << '\n');
|
|
return New;
|
|
}
|
|
|
|
/// ConvertShiftToMul - 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);
|
|
Shl->replaceAllUsesWith(Mul);
|
|
Mul->setDebugLoc(Shl->getDebugLoc());
|
|
return Mul;
|
|
}
|
|
|
|
/// FindInOperandList - 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(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;
|
|
// Scan backwards.
|
|
for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j)
|
|
if (Ops[j].Op == X)
|
|
return j;
|
|
return i;
|
|
}
|
|
|
|
/// EmitAddTreeOfValues - Emit a tree of add instructions, summing Ops together
|
|
/// and returning the result. Insert the tree before I.
|
|
static Value *EmitAddTreeOfValues(Instruction *I,
|
|
SmallVectorImpl<WeakVH> &Ops){
|
|
if (Ops.size() == 1) return Ops.back();
|
|
|
|
Value *V1 = Ops.back();
|
|
Ops.pop_back();
|
|
Value *V2 = EmitAddTreeOfValues(I, Ops);
|
|
return CreateAdd(V2, V1, "tmp", I, I);
|
|
}
|
|
|
|
/// RemoveFactorFromExpression - 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 *Reassociate::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)) {
|
|
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; ++InsertPt;
|
|
|
|
// 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;
|
|
}
|
|
|
|
/// FindSingleUseMultiplyFactors - 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,
|
|
const SmallVectorImpl<ValueEntry> &Ops) {
|
|
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, Ops);
|
|
FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops);
|
|
}
|
|
|
|
/// OptimizeAndOrXor - 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());
|
|
if (BinaryOperator::isNot(Ops[i].Op)) { // Cannot occur for ^.
|
|
Value *X = BinaryOperator::getNotArgument(Ops[i].Op);
|
|
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 funciton 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 != 0) {
|
|
if (!ConstOpnd.isAllOnesValue()) {
|
|
LLVMContext &Ctx = Opnd->getType()->getContext();
|
|
Instruction *I;
|
|
I = BinaryOperator::CreateAnd(Opnd, ConstantInt::get(Ctx, ConstOpnd),
|
|
"and.ra", InsertBefore);
|
|
I->setDebugLoc(InsertBefore->getDebugLoc());
|
|
return I;
|
|
}
|
|
return Opnd;
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
// 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 Reassociate::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() != 0) {
|
|
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;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
|
|
// 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 Reassociate::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 != 0 && !C3.isAllOnesValue()) {
|
|
int NewInstNum = ConstOpnd != 0 ? 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 != 0 && !C3.isAllOnesValue()) {
|
|
int NewInstNum = ConstOpnd != 0 ? 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 *Reassociate::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->getIntegerBitWidth(), 0);
|
|
|
|
// Step 1: Convert ValueEntry to XorOpnd
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
Value *V = Ops[i].Op;
|
|
if (!isa<ConstantInt>(V)) {
|
|
XorOpnd O(V);
|
|
O.setSymbolicRank(getRank(O.getSymbolicPart()));
|
|
Opnds.push_back(O);
|
|
} else
|
|
ConstOpnd ^= cast<ConstantInt>(V)->getValue();
|
|
}
|
|
|
|
// 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").
|
|
std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(), XorOpnd::PtrSortFunctor());
|
|
|
|
// 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 != 0 && 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 != 0) {
|
|
Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
|
|
ValueEntry VE(getRank(C), C);
|
|
Ops.push_back(VE);
|
|
}
|
|
int Sz = Ops.size();
|
|
if (Sz == 1)
|
|
return Ops.back().Op;
|
|
else if (Sz == 0) {
|
|
assert(ConstOpnd == 0);
|
|
return ConstantInt::get(Ty->getContext(), ConstOpnd);
|
|
}
|
|
}
|
|
|
|
return nullptr;
|
|
}
|
|
|
|
/// OptimizeAdd - 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 *Reassociate::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);
|
|
|
|
DEBUG(errs() << "\nFACTORING [" << NumFound << "]: " << *TheOp << '\n');
|
|
++NumFactor;
|
|
|
|
// Insert a new multiply.
|
|
Type *Ty = TheOp->getType();
|
|
Constant *C = Ty->isIntegerTy() ? 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.
|
|
if (!BinaryOperator::isNeg(TheOp) && !BinaryOperator::isFNeg(TheOp) &&
|
|
!BinaryOperator::isNot(TheOp))
|
|
continue;
|
|
|
|
Value *X = nullptr;
|
|
if (BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp))
|
|
X = BinaryOperator::getNegArgument(TheOp);
|
|
else if (BinaryOperator::isNot(TheOp))
|
|
X = BinaryOperator::getNotArgument(TheOp);
|
|
|
|
unsigned FoundX = FindInOperandList(Ops, i, X);
|
|
if (FoundX == i)
|
|
continue;
|
|
|
|
// Remove X and -X from the operand list.
|
|
if (Ops.size() == 2 &&
|
|
(BinaryOperator::isNeg(TheOp) || BinaryOperator::isFNeg(TheOp)))
|
|
return Constant::getNullValue(X->getType());
|
|
|
|
// Remove X and ~X from the operand list.
|
|
if (Ops.size() == 2 && BinaryOperator::isNot(TheOp))
|
|
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 (BinaryOperator::isNot(TheOp)) {
|
|
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, Ops);
|
|
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))
|
|
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());
|
|
assert(!Duplicates.count(Factor) &&
|
|
"Shouldn't have two constant factors, missed a canonicalize");
|
|
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);
|
|
assert(!Duplicates.count(Factor) &&
|
|
"Shouldn't have two constant factors, missed a canonicalize");
|
|
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) {
|
|
DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
|
|
++NumFactor;
|
|
|
|
// Create a new instruction that uses the MaxOccVal twice. If we don't do
|
|
// this, we could otherwise run into situations where removing a factor
|
|
// from an expression will drop a use of maxocc, and this can cause
|
|
// RemoveFactorFromExpression on successive values to behave differently.
|
|
Instruction *DummyInst =
|
|
I->getType()->isIntegerTy()
|
|
? BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal)
|
|
: BinaryOperator::CreateFAdd(MaxOccVal, MaxOccVal);
|
|
|
|
SmallVector<WeakVH, 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.
|
|
delete DummyInst;
|
|
|
|
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, "tmp", 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;
|
|
}
|
|
|
|
/// \brief 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.
|
|
bool Reassociate::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);
|
|
|
|
std::stable_sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
|
|
return true;
|
|
}
|
|
|
|
/// \brief 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()->isIntegerTy())
|
|
LHS = Builder.CreateMul(LHS, Ops.pop_back_val());
|
|
else
|
|
LHS = Builder.CreateFMul(LHS, Ops.pop_back_val());
|
|
} while (!Ops.empty());
|
|
|
|
return LHS;
|
|
}
|
|
|
|
/// \brief 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 *Reassociate::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(),
|
|
Factor::PowerEqual()),
|
|
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 *Reassociate::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);
|
|
Value *V = buildMinimalMultiplyDAG(Builder, Factors);
|
|
if (Ops.empty())
|
|
return V;
|
|
|
|
ValueEntry NewEntry = ValueEntry(getRank(V), V);
|
|
Ops.insert(std::lower_bound(Ops.begin(), Ops.end(), NewEntry), NewEntry);
|
|
return nullptr;
|
|
}
|
|
|
|
Value *Reassociate::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;
|
|
}
|
|
|
|
/// EraseInst - Zap the given instruction, adding interesting operands to the
|
|
/// work list.
|
|
void Reassociate::EraseInst(Instruction *I) {
|
|
assert(isInstructionTriviallyDead(I) && "Trivially dead instructions only!");
|
|
SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
|
|
// Erase the dead instruction.
|
|
ValueRankMap.erase(I);
|
|
RedoInsts.remove(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))
|
|
Op = Op->user_back();
|
|
RedoInsts.insert(Op);
|
|
}
|
|
}
|
|
|
|
void Reassociate::optimizeFAddNegExpr(ConstantFP *ConstOperand, Instruction *I,
|
|
int OperandNr) {
|
|
// Change the sign of the constant.
|
|
APFloat Val = ConstOperand->getValueAPF();
|
|
Val.changeSign();
|
|
I->setOperand(0, ConstantFP::get(ConstOperand->getContext(), Val));
|
|
|
|
assert(I->hasOneUse() && "Only a single use can be replaced.");
|
|
Instruction *Parent = I->user_back();
|
|
|
|
Value *OtherOperand = Parent->getOperand(1 - OperandNr);
|
|
|
|
unsigned Opcode = Parent->getOpcode();
|
|
assert(Opcode == Instruction::FAdd ||
|
|
(Opcode == Instruction::FSub && Parent->getOperand(1) == I));
|
|
|
|
BinaryOperator *NI = Opcode == Instruction::FAdd
|
|
? BinaryOperator::CreateFSub(OtherOperand, I)
|
|
: BinaryOperator::CreateFAdd(OtherOperand, I);
|
|
NI->setFastMathFlags(cast<FPMathOperator>(Parent)->getFastMathFlags());
|
|
NI->insertBefore(Parent);
|
|
NI->setName(Parent->getName() + ".repl");
|
|
Parent->replaceAllUsesWith(NI);
|
|
NI->setDebugLoc(I->getDebugLoc());
|
|
MadeChange = true;
|
|
}
|
|
|
|
/// OptimizeInst - Inspect and optimize the given instruction. Note that erasing
|
|
/// instructions is not allowed.
|
|
void Reassociate::OptimizeInst(Instruction *I) {
|
|
// Only consider operations that we understand.
|
|
if (!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 floating point binary operators, to canonicalize the order of their
|
|
// operands. This can potentially expose more CSE opportunities, and makes
|
|
// writing other transformations simpler.
|
|
if (I->getType()->isFloatingPointTy() || I->getType()->isVectorTy()) {
|
|
|
|
// FAdd and FMul can be commuted.
|
|
unsigned Opcode = I->getOpcode();
|
|
if (Opcode == Instruction::FMul || Opcode == Instruction::FAdd) {
|
|
Value *LHS = I->getOperand(0);
|
|
Value *RHS = I->getOperand(1);
|
|
unsigned LHSRank = getRank(LHS);
|
|
unsigned RHSRank = getRank(RHS);
|
|
|
|
// Sort the operands by rank.
|
|
if (RHSRank < LHSRank) {
|
|
I->setOperand(0, RHS);
|
|
I->setOperand(1, LHS);
|
|
}
|
|
}
|
|
|
|
// Reassociate: x + -ConstantFP * y -> x - ConstantFP * y
|
|
// The FMul can also be an FDiv, and FAdd can be a FSub.
|
|
if (Opcode == Instruction::FMul || Opcode == Instruction::FDiv) {
|
|
if (ConstantFP *LHSConst = dyn_cast<ConstantFP>(I->getOperand(0))) {
|
|
if (LHSConst->isNegative() && I->hasOneUse()) {
|
|
Instruction *Parent = I->user_back();
|
|
if (Parent->getOpcode() == Instruction::FAdd) {
|
|
if (Parent->getOperand(0) == I)
|
|
optimizeFAddNegExpr(LHSConst, I, 0);
|
|
else if (Parent->getOperand(1) == I)
|
|
optimizeFAddNegExpr(LHSConst, I, 1);
|
|
} else if (Parent->getOpcode() == Instruction::FSub)
|
|
if (Parent->getOperand(1) == I)
|
|
optimizeFAddNegExpr(LHSConst, I, 1);
|
|
}
|
|
}
|
|
}
|
|
|
|
// FIXME: We should commute vector instructions as well. However, this
|
|
// requires further analysis to determine the effect on later passes.
|
|
|
|
// Don't try to optimize vector instructions or anything that doesn't have
|
|
// unsafe algebra.
|
|
if (I->getType()->isVectorTy() || !I->hasUnsafeAlgebra())
|
|
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.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
} else if (BinaryOperator::isNeg(I)) {
|
|
// 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);
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
}
|
|
}
|
|
} else if (I->getOpcode() == Instruction::FSub) {
|
|
if (ShouldBreakUpSubtract(I)) {
|
|
Instruction *NI = BreakUpSubtract(I);
|
|
RedoInsts.insert(I);
|
|
MadeChange = true;
|
|
I = NI;
|
|
} else if (BinaryOperator::isFNeg(I)) {
|
|
// 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::FMul) &&
|
|
(!I->hasOneUse() ||
|
|
!isReassociableOp(I->user_back(), Instruction::FMul))) {
|
|
Instruction *NI = LowerNegateToMultiply(I);
|
|
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)
|
|
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 Reassociate::ReassociateExpression(BinaryOperator *I) {
|
|
assert(!I->getType()->isVectorTy() &&
|
|
"Reassociation of vector instructions is not supported.");
|
|
|
|
// 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));
|
|
}
|
|
|
|
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.
|
|
std::stable_sort(Ops.begin(), Ops.end());
|
|
|
|
// OptimizeExpression - 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.
|
|
DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
|
|
I->replaceAllUsesWith(V);
|
|
if (Instruction *VI = dyn_cast<Instruction>(V))
|
|
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)->isAllOnesValue()) {
|
|
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);
|
|
}
|
|
}
|
|
|
|
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;
|
|
}
|
|
|
|
// Now that we ordered and optimized the expressions, splat them back into
|
|
// the expression tree, removing any unneeded nodes.
|
|
RewriteExprTree(I, Ops);
|
|
}
|
|
|
|
bool Reassociate::runOnFunction(Function &F) {
|
|
if (skipOptnoneFunction(F))
|
|
return false;
|
|
|
|
// Calculate the rank map for F
|
|
BuildRankMap(F);
|
|
|
|
MadeChange = false;
|
|
for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
|
|
// Optimize every instruction in the basic block.
|
|
for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE; )
|
|
if (isInstructionTriviallyDead(II)) {
|
|
EraseInst(II++);
|
|
} else {
|
|
OptimizeInst(II);
|
|
assert(II->getParent() == BI && "Moved to a different block!");
|
|
++II;
|
|
}
|
|
|
|
// If this produced extra instructions to optimize, handle them now.
|
|
while (!RedoInsts.empty()) {
|
|
Instruction *I = RedoInsts.pop_back_val();
|
|
if (isInstructionTriviallyDead(I))
|
|
EraseInst(I);
|
|
else
|
|
OptimizeInst(I);
|
|
}
|
|
}
|
|
|
|
// We are done with the rank map.
|
|
RankMap.clear();
|
|
ValueRankMap.clear();
|
|
|
|
return MadeChange;
|
|
}
|