134 lines
4.6 KiB
C++
134 lines
4.6 KiB
C++
//===- Reassociate.h - Reassociate binary expressions -----------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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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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#ifndef LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H
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#define LLVM_TRANSFORMS_SCALAR_REASSOCIATE_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/SetVector.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/IR/ValueHandle.h"
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#include <deque>
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namespace llvm {
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class APInt;
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class BasicBlock;
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class BinaryOperator;
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class Function;
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class Instruction;
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class IRBuilderBase;
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class Value;
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/// A private "module" namespace for types and utilities used by Reassociate.
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/// These are implementation details and should not be used by clients.
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namespace reassociate {
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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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/// 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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};
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class XorOpnd;
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} // end namespace reassociate
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/// Reassociate commutative expressions.
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class ReassociatePass : public PassInfoMixin<ReassociatePass> {
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public:
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using OrderedSet =
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SetVector<AssertingVH<Instruction>, std::deque<AssertingVH<Instruction>>>;
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protected:
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DenseMap<BasicBlock *, unsigned> RankMap;
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DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
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OrderedSet RedoInsts;
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// Arbitrary, but prevents quadratic behavior.
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static const unsigned GlobalReassociateLimit = 10;
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static const unsigned NumBinaryOps =
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Instruction::BinaryOpsEnd - Instruction::BinaryOpsBegin;
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struct PairMapValue {
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WeakVH Value1;
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WeakVH Value2;
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unsigned Score;
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bool isValid() const { return Value1 && Value2; }
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};
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DenseMap<std::pair<Value *, Value *>, PairMapValue> PairMap[NumBinaryOps];
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bool MadeChange;
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public:
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PreservedAnalyses run(Function &F, FunctionAnalysisManager &);
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private:
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void BuildRankMap(Function &F, ReversePostOrderTraversal<Function *> &RPOT);
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unsigned getRank(Value *V);
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void canonicalizeOperands(Instruction *I);
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void ReassociateExpression(BinaryOperator *I);
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void RewriteExprTree(BinaryOperator *I,
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SmallVectorImpl<reassociate::ValueEntry> &Ops);
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Value *OptimizeExpression(BinaryOperator *I,
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SmallVectorImpl<reassociate::ValueEntry> &Ops);
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Value *OptimizeAdd(Instruction *I,
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SmallVectorImpl<reassociate::ValueEntry> &Ops);
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Value *OptimizeXor(Instruction *I,
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SmallVectorImpl<reassociate::ValueEntry> &Ops);
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bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1,
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APInt &ConstOpnd, Value *&Res);
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bool CombineXorOpnd(Instruction *I, reassociate::XorOpnd *Opnd1,
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reassociate::XorOpnd *Opnd2, APInt &ConstOpnd,
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Value *&Res);
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Value *buildMinimalMultiplyDAG(IRBuilderBase &Builder,
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SmallVectorImpl<reassociate::Factor> &Factors);
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Value *OptimizeMul(BinaryOperator *I,
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SmallVectorImpl<reassociate::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 RecursivelyEraseDeadInsts(Instruction *I, OrderedSet &Insts);
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void OptimizeInst(Instruction *I);
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Instruction *canonicalizeNegFPConstantsForOp(Instruction *I, Instruction *Op,
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Value *OtherOp);
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Instruction *canonicalizeNegFPConstants(Instruction *I);
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void BuildPairMap(ReversePostOrderTraversal<Function *> &RPOT);
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};
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} // end namespace llvm
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#endif // LLVM_TRANSFORMS_SCALAR_REASSOCIATE_H
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