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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59844 91177308-0d34-0410-b5e6-96231b3b80d8
888 lines
32 KiB
C++
888 lines
32 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...
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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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#define DEBUG_TYPE "reassociate"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Function.h"
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#include "llvm/Instructions.h"
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#include "llvm/Pass.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/Statistic.h"
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#include <algorithm>
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#include <map>
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using namespace llvm;
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STATISTIC(NumLinear , "Number of insts linearized");
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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 VISIBILITY_HIDDEN 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 std::vector<ValueEntry> &Ops) {
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Module *M = I->getParent()->getParent()->getParent();
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cerr << Instruction::getOpcodeName(I->getOpcode()) << " "
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<< *Ops[0].Op->getType();
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for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
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WriteAsOperand(*cerr.stream() << " ", Ops[i].Op, false, M);
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cerr << "," << 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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class VISIBILITY_HIDDEN Reassociate : public FunctionPass {
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std::map<BasicBlock*, unsigned> RankMap;
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std::map<Value*, unsigned> ValueRankMap;
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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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bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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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, std::vector<ValueEntry> &Ops,
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unsigned Idx = 0);
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Value *OptimizeExpression(BinaryOperator *I, std::vector<ValueEntry> &Ops);
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void LinearizeExprTree(BinaryOperator *I, std::vector<ValueEntry> &Ops);
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void LinearizeExpr(BinaryOperator *I);
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Value *RemoveFactorFromExpression(Value *V, Value *Factor);
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void ReassociateBB(BasicBlock *BB);
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void RemoveDeadBinaryOp(Value *V);
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};
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}
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char Reassociate::ID = 0;
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static RegisterPass<Reassociate> X("reassociate", "Reassociate expressions");
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// Public interface to the Reassociate pass
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FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
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void Reassociate::RemoveDeadBinaryOp(Value *V) {
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Instruction *Op = dyn_cast<Instruction>(V);
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if (!Op || !isa<BinaryOperator>(Op) || !isa<CmpInst>(Op) || !Op->use_empty())
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return;
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Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
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RemoveDeadBinaryOp(LHS);
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RemoveDeadBinaryOp(RHS);
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}
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static bool isUnmovableInstruction(Instruction *I) {
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if (I->getOpcode() == Instruction::PHI ||
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I->getOpcode() == Instruction::Alloca ||
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I->getOpcode() == Instruction::Load ||
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I->getOpcode() == Instruction::Malloc ||
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I->getOpcode() == Instruction::Invoke ||
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I->getOpcode() == Instruction::Call ||
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I->getOpcode() == Instruction::UDiv ||
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I->getOpcode() == Instruction::SDiv ||
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I->getOpcode() == Instruction::FDiv ||
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I->getOpcode() == Instruction::URem ||
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I->getOpcode() == Instruction::SRem ||
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I->getOpcode() == Instruction::FRem)
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return true;
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return false;
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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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if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument...
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Instruction *I = dyn_cast<Instruction>(V);
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if (I == 0) return 0; // Otherwise it's a global or constant, rank 0.
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unsigned &CachedRank = ValueRankMap[I];
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if (CachedRank) return CachedRank; // 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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if (!I->getType()->isInteger() ||
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(!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I)))
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++Rank;
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//DOUT << "Calculated Rank[" << V->getName() << "] = "
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// << Rank << "\n";
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return CachedRank = Rank;
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}
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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() || V->use_empty()) && 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 0;
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}
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/// LowerNegateToMultiply - Replace 0-X with X*-1.
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///
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static Instruction *LowerNegateToMultiply(Instruction *Neg) {
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Constant *Cst = ConstantInt::getAllOnesValue(Neg->getType());
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Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
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Res->takeName(Neg);
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Neg->replaceAllUsesWith(Res);
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Neg->eraseFromParent();
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return Res;
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}
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// Given an expression of the form '(A+B)+(D+C)', turn it into '(((A+B)+C)+D)'.
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// Note that if D is also part of the expression tree that we recurse to
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// linearize it as well. Besides that case, this does not recurse into A,B, or
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// C.
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void Reassociate::LinearizeExpr(BinaryOperator *I) {
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BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
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BinaryOperator *RHS = cast<BinaryOperator>(I->getOperand(1));
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assert(isReassociableOp(LHS, I->getOpcode()) &&
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isReassociableOp(RHS, I->getOpcode()) &&
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"Not an expression that needs linearization?");
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DOUT << "Linear" << *LHS << *RHS << *I;
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// Move the RHS instruction to live immediately before I, avoiding breaking
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// dominator properties.
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RHS->moveBefore(I);
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// Move operands around to do the linearization.
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I->setOperand(1, RHS->getOperand(0));
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RHS->setOperand(0, LHS);
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I->setOperand(0, RHS);
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++NumLinear;
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MadeChange = true;
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DOUT << "Linearized: " << *I;
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// If D is part of this expression tree, tail recurse.
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if (isReassociableOp(I->getOperand(1), I->getOpcode()))
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LinearizeExpr(I);
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}
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/// LinearizeExprTree - Given an associative binary expression tree, traverse
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/// all of the uses putting it into canonical form. This forces a left-linear
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/// form of the the expression (((a+b)+c)+d), and collects information about the
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/// rank of the non-tree operands.
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///
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/// NOTE: These intentionally destroys the expression tree operands (turning
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/// them into undef values) to reduce #uses of the values. This means that the
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/// caller MUST use something like RewriteExprTree to put the values back in.
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///
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void Reassociate::LinearizeExprTree(BinaryOperator *I,
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std::vector<ValueEntry> &Ops) {
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Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
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unsigned Opcode = I->getOpcode();
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// First step, linearize the expression if it is in ((A+B)+(C+D)) form.
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BinaryOperator *LHSBO = isReassociableOp(LHS, Opcode);
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BinaryOperator *RHSBO = isReassociableOp(RHS, Opcode);
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// If this is a multiply expression tree and it contains internal negations,
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// transform them into multiplies by -1 so they can be reassociated.
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if (I->getOpcode() == Instruction::Mul) {
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if (!LHSBO && LHS->hasOneUse() && BinaryOperator::isNeg(LHS)) {
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LHS = LowerNegateToMultiply(cast<Instruction>(LHS));
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LHSBO = isReassociableOp(LHS, Opcode);
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}
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if (!RHSBO && RHS->hasOneUse() && BinaryOperator::isNeg(RHS)) {
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RHS = LowerNegateToMultiply(cast<Instruction>(RHS));
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RHSBO = isReassociableOp(RHS, Opcode);
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}
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}
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if (!LHSBO) {
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if (!RHSBO) {
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// Neither the LHS or RHS as part of the tree, thus this is a leaf. As
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// such, just remember these operands and their rank.
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Ops.push_back(ValueEntry(getRank(LHS), LHS));
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Ops.push_back(ValueEntry(getRank(RHS), RHS));
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// Clear the leaves out.
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I->setOperand(0, UndefValue::get(I->getType()));
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I->setOperand(1, UndefValue::get(I->getType()));
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return;
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} else {
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// Turn X+(Y+Z) -> (Y+Z)+X
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std::swap(LHSBO, RHSBO);
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std::swap(LHS, RHS);
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bool Success = !I->swapOperands();
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assert(Success && "swapOperands failed");
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Success = false;
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MadeChange = true;
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}
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} else if (RHSBO) {
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// Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the the RHS is not
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// part of the expression tree.
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LinearizeExpr(I);
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LHS = LHSBO = cast<BinaryOperator>(I->getOperand(0));
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RHS = I->getOperand(1);
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RHSBO = 0;
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}
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// Okay, now we know that the LHS is a nested expression and that the RHS is
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// not. Perform reassociation.
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assert(!isReassociableOp(RHS, Opcode) && "LinearizeExpr failed!");
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// Move LHS right before I to make sure that the tree expression dominates all
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// values.
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LHSBO->moveBefore(I);
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// Linearize the expression tree on the LHS.
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LinearizeExprTree(LHSBO, Ops);
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// Remember the RHS operand and its rank.
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Ops.push_back(ValueEntry(getRank(RHS), RHS));
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// Clear the RHS leaf out.
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I->setOperand(1, UndefValue::get(I->getType()));
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}
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// RewriteExprTree - Now that the operands for this expression tree are
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// linearized and optimized, emit them in-order. This function is written to be
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// tail recursive.
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void Reassociate::RewriteExprTree(BinaryOperator *I,
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std::vector<ValueEntry> &Ops,
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unsigned i) {
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if (i+2 == Ops.size()) {
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if (I->getOperand(0) != Ops[i].Op ||
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I->getOperand(1) != Ops[i+1].Op) {
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Value *OldLHS = I->getOperand(0);
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DOUT << "RA: " << *I;
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I->setOperand(0, Ops[i].Op);
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I->setOperand(1, Ops[i+1].Op);
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DOUT << "TO: " << *I;
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MadeChange = true;
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++NumChanged;
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// If we reassociated a tree to fewer operands (e.g. (1+a+2) -> (a+3)
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// delete the extra, now dead, nodes.
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RemoveDeadBinaryOp(OldLHS);
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}
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return;
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}
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assert(i+2 < Ops.size() && "Ops index out of range!");
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if (I->getOperand(1) != Ops[i].Op) {
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DOUT << "RA: " << *I;
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I->setOperand(1, Ops[i].Op);
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DOUT << "TO: " << *I;
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MadeChange = true;
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++NumChanged;
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}
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BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
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assert(LHS->getOpcode() == I->getOpcode() &&
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"Improper expression tree!");
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// Compactify the tree instructions together with each other to guarantee
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// that the expression tree is dominated by all of Ops.
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LHS->moveBefore(I);
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RewriteExprTree(LHS, Ops, i+1);
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}
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// NegateValue - Insert instructions before the instruction pointed to by BI,
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// that computes the negative version of the value specified. The negative
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// version of the value is returned, and BI is left pointing at the instruction
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// that should be processed next by the reassociation pass.
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//
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static Value *NegateValue(Value *V, Instruction *BI) {
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// We are trying to expose opportunity for reassociation. One of the things
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// that we want to do to achieve this is to push a negation as deep into an
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// expression chain as possible, to expose the add instructions. In practice,
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// this means that we turn this:
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// X = -(A+12+C+D) into X = -A + -12 + -C + -D = -12 + -A + -C + -D
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// so that later, a: Y = 12+X could get reassociated with the -12 to eliminate
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// the constants. We assume that instcombine will clean up the mess later if
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// we introduce tons of unnecessary negation instructions...
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//
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if (Instruction *I = dyn_cast<Instruction>(V))
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if (I->getOpcode() == Instruction::Add && I->hasOneUse()) {
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// Push the negates through the add.
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I->setOperand(0, NegateValue(I->getOperand(0), BI));
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I->setOperand(1, NegateValue(I->getOperand(1), BI));
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// We must move the add instruction here, because the neg instructions do
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// not dominate the old add instruction in general. By moving it, we are
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// assured that the neg instructions we just inserted dominate the
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// instruction we are about to insert after them.
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//
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I->moveBefore(BI);
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I->setName(I->getName()+".neg");
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return I;
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}
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// Insert a 'neg' instruction that subtracts the value from zero to get the
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// negation.
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//
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return BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI);
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}
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/// ShouldBreakUpSubtract - Return true if we should break up this subtract of
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/// X-Y into (X + -Y).
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static bool ShouldBreakUpSubtract(Instruction *Sub) {
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// If this is a negation, we can't split it up!
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if (BinaryOperator::isNeg(Sub))
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return false;
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// Don't bother to break this up unless either the LHS is an associable add or
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// subtract or if this is only used by one.
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if (isReassociableOp(Sub->getOperand(0), Instruction::Add) ||
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isReassociableOp(Sub->getOperand(0), Instruction::Sub))
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return true;
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if (isReassociableOp(Sub->getOperand(1), Instruction::Add) ||
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isReassociableOp(Sub->getOperand(1), Instruction::Sub))
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return true;
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if (Sub->hasOneUse() &&
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(isReassociableOp(Sub->use_back(), Instruction::Add) ||
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isReassociableOp(Sub->use_back(), Instruction::Sub)))
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return true;
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return false;
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}
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/// BreakUpSubtract - If we have (X-Y), and if either X is an add, or if this is
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/// only used by an add, transform this into (X+(0-Y)) to promote better
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/// reassociation.
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static Instruction *BreakUpSubtract(Instruction *Sub) {
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// Convert a subtract into an add and a neg instruction... so that sub
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// instructions can be commuted with other add instructions...
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//
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// Calculate the negative value of Operand 1 of the sub instruction...
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// and set it as the RHS of the add instruction we just made...
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//
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Value *NegVal = NegateValue(Sub->getOperand(1), Sub);
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Instruction *New =
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BinaryOperator::CreateAdd(Sub->getOperand(0), NegVal, "", Sub);
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New->takeName(Sub);
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// Everyone now refers to the add instruction.
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Sub->replaceAllUsesWith(New);
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Sub->eraseFromParent();
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DOUT << "Negated: " << *New;
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return New;
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}
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/// ConvertShiftToMul - If this is a shift of a reassociable multiply or is used
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/// by one, change this into a multiply by a constant to assist with further
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/// reassociation.
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static Instruction *ConvertShiftToMul(Instruction *Shl) {
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// If an operand of this shift is a reassociable multiply, or if the shift
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// is used by a reassociable multiply or add, turn into a multiply.
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if (isReassociableOp(Shl->getOperand(0), Instruction::Mul) ||
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(Shl->hasOneUse() &&
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(isReassociableOp(Shl->use_back(), Instruction::Mul) ||
|
|
isReassociableOp(Shl->use_back(), Instruction::Add)))) {
|
|
Constant *MulCst = ConstantInt::get(Shl->getType(), 1);
|
|
MulCst = ConstantExpr::getShl(MulCst, cast<Constant>(Shl->getOperand(1)));
|
|
|
|
Instruction *Mul = BinaryOperator::CreateMul(Shl->getOperand(0), MulCst,
|
|
"", Shl);
|
|
Mul->takeName(Shl);
|
|
Shl->replaceAllUsesWith(Mul);
|
|
Shl->eraseFromParent();
|
|
return Mul;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
// 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.
|
|
static unsigned FindInOperandList(std::vector<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, std::vector<Value*> &Ops) {
|
|
if (Ops.size() == 1) return Ops.back();
|
|
|
|
Value *V1 = Ops.back();
|
|
Ops.pop_back();
|
|
Value *V2 = EmitAddTreeOfValues(I, Ops);
|
|
return BinaryOperator::CreateAdd(V2, V1, "tmp", 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);
|
|
if (!BO) return 0;
|
|
|
|
std::vector<ValueEntry> Factors;
|
|
LinearizeExprTree(BO, Factors);
|
|
|
|
bool FoundFactor = 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 (!FoundFactor) {
|
|
// Make sure to restore the operands to the expression tree.
|
|
RewriteExprTree(BO, Factors);
|
|
return 0;
|
|
}
|
|
|
|
if (Factors.size() == 1) return Factors[0].Op;
|
|
|
|
RewriteExprTree(BO, Factors);
|
|
return BO;
|
|
}
|
|
|
|
/// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
|
|
/// add its operands as factors, otherwise add V to the list of factors.
|
|
static void FindSingleUseMultiplyFactors(Value *V,
|
|
std::vector<Value*> &Factors) {
|
|
BinaryOperator *BO;
|
|
if ((!V->hasOneUse() && !V->use_empty()) ||
|
|
!(BO = dyn_cast<BinaryOperator>(V)) ||
|
|
BO->getOpcode() != Instruction::Mul) {
|
|
Factors.push_back(V);
|
|
return;
|
|
}
|
|
|
|
// Otherwise, add the LHS and RHS to the list of factors.
|
|
FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
|
|
FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
|
|
}
|
|
|
|
|
|
|
|
Value *Reassociate::OptimizeExpression(BinaryOperator *I,
|
|
std::vector<ValueEntry> &Ops) {
|
|
// Now that we have the linearized expression tree, try to optimize it.
|
|
// Start by folding any constants that we found.
|
|
bool IterateOptimization = false;
|
|
if (Ops.size() == 1) return Ops[0].Op;
|
|
|
|
unsigned Opcode = I->getOpcode();
|
|
|
|
if (Constant *V1 = dyn_cast<Constant>(Ops[Ops.size()-2].Op))
|
|
if (Constant *V2 = dyn_cast<Constant>(Ops.back().Op)) {
|
|
Ops.pop_back();
|
|
Ops.back().Op = ConstantExpr::get(Opcode, V1, V2);
|
|
return OptimizeExpression(I, Ops);
|
|
}
|
|
|
|
// Check for destructive annihilation due to a constant being used.
|
|
if (ConstantInt *CstVal = dyn_cast<ConstantInt>(Ops.back().Op))
|
|
switch (Opcode) {
|
|
default: break;
|
|
case Instruction::And:
|
|
if (CstVal->isZero()) { // ... & 0 -> 0
|
|
++NumAnnihil;
|
|
return CstVal;
|
|
} else if (CstVal->isAllOnesValue()) { // ... & -1 -> ...
|
|
Ops.pop_back();
|
|
}
|
|
break;
|
|
case Instruction::Mul:
|
|
if (CstVal->isZero()) { // ... * 0 -> 0
|
|
++NumAnnihil;
|
|
return CstVal;
|
|
} else if (cast<ConstantInt>(CstVal)->isOne()) {
|
|
Ops.pop_back(); // ... * 1 -> ...
|
|
}
|
|
break;
|
|
case Instruction::Or:
|
|
if (CstVal->isAllOnesValue()) { // ... | -1 -> -1
|
|
++NumAnnihil;
|
|
return CstVal;
|
|
}
|
|
// FALLTHROUGH!
|
|
case Instruction::Add:
|
|
case Instruction::Xor:
|
|
if (CstVal->isZero()) // ... [|^+] 0 -> ...
|
|
Ops.pop_back();
|
|
break;
|
|
}
|
|
if (Ops.size() == 1) return Ops[0].Op;
|
|
|
|
// Handle destructive annihilation do to identities between elements in the
|
|
// argument list here.
|
|
switch (Opcode) {
|
|
default: break;
|
|
case Instruction::And:
|
|
case Instruction::Or:
|
|
case Instruction::Xor:
|
|
// 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
|
|
++NumAnnihil;
|
|
return Constant::getNullValue(X->getType());
|
|
} else if (Opcode == Instruction::Or) { // ...|X|~X = -1
|
|
++NumAnnihil;
|
|
return ConstantInt::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.
|
|
Ops.erase(Ops.begin()+i);
|
|
--i; --e;
|
|
IterateOptimization = true;
|
|
++NumAnnihil;
|
|
} else {
|
|
assert(Opcode == Instruction::Xor);
|
|
if (e == 2) {
|
|
++NumAnnihil;
|
|
return Constant::getNullValue(Ops[0].Op->getType());
|
|
}
|
|
// ... X^X -> ...
|
|
Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
|
|
i -= 1; e -= 2;
|
|
IterateOptimization = true;
|
|
++NumAnnihil;
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
|
|
case Instruction::Add:
|
|
// Scan the operand lists looking for X and -X pairs. If we find any, we
|
|
// can simplify the expression. X+-X == 0.
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
assert(i < Ops.size());
|
|
// Check for X and -X in the operand list.
|
|
if (BinaryOperator::isNeg(Ops[i].Op)) {
|
|
Value *X = BinaryOperator::getNegArgument(Ops[i].Op);
|
|
unsigned FoundX = FindInOperandList(Ops, i, X);
|
|
if (FoundX != i) {
|
|
// Remove X and -X from the operand list.
|
|
if (Ops.size() == 2) {
|
|
++NumAnnihil;
|
|
return Constant::getNullValue(X->getType());
|
|
} else {
|
|
Ops.erase(Ops.begin()+i);
|
|
if (i < FoundX)
|
|
--FoundX;
|
|
else
|
|
--i; // Need to back up an extra one.
|
|
Ops.erase(Ops.begin()+FoundX);
|
|
IterateOptimization = true;
|
|
++NumAnnihil;
|
|
--i; // Revisit element.
|
|
e -= 2; // Removed two elements.
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
// 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.
|
|
std::map<Value*, unsigned> FactorOccurrences;
|
|
unsigned MaxOcc = 0;
|
|
Value *MaxOccVal = 0;
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
if (BinaryOperator *BOp = dyn_cast<BinaryOperator>(Ops[i].Op)) {
|
|
if (BOp->getOpcode() == Instruction::Mul && BOp->use_empty()) {
|
|
// Compute all of the factors of this added value.
|
|
std::vector<Value*> Factors;
|
|
FindSingleUseMultiplyFactors(BOp, Factors);
|
|
assert(Factors.size() > 1 && "Bad linearize!");
|
|
|
|
// Add one to FactorOccurrences for each unique factor in this op.
|
|
if (Factors.size() == 2) {
|
|
unsigned Occ = ++FactorOccurrences[Factors[0]];
|
|
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[0]; }
|
|
if (Factors[0] != Factors[1]) { // Don't double count A*A.
|
|
Occ = ++FactorOccurrences[Factors[1]];
|
|
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[1]; }
|
|
}
|
|
} else {
|
|
std::set<Value*> Duplicates;
|
|
for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
|
|
if (Duplicates.insert(Factors[i]).second) {
|
|
unsigned Occ = ++FactorOccurrences[Factors[i]];
|
|
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[i]; }
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// If any factor occurred more than one time, we can pull it out.
|
|
if (MaxOcc > 1) {
|
|
DOUT << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << "\n";
|
|
|
|
// 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 = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
|
|
std::vector<Value*> NewMulOps;
|
|
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
|
|
if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
|
|
NewMulOps.push_back(V);
|
|
Ops.erase(Ops.begin()+i);
|
|
--i; --e;
|
|
}
|
|
}
|
|
|
|
// No need for extra uses anymore.
|
|
delete DummyInst;
|
|
|
|
unsigned NumAddedValues = NewMulOps.size();
|
|
Value *V = EmitAddTreeOfValues(I, NewMulOps);
|
|
Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
|
|
|
|
// Now that we have inserted V and its sole use, 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))
|
|
if (NumAddedValues > 1)
|
|
ReassociateExpression(cast<BinaryOperator>(V));
|
|
|
|
++NumFactor;
|
|
|
|
if (Ops.empty())
|
|
return V2;
|
|
|
|
// Add the new value to the list of things being added.
|
|
Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
|
|
|
|
// Rewrite the tree so that there is now a use of V.
|
|
RewriteExprTree(I, Ops);
|
|
return OptimizeExpression(I, Ops);
|
|
}
|
|
break;
|
|
//case Instruction::Mul:
|
|
}
|
|
|
|
if (IterateOptimization)
|
|
return OptimizeExpression(I, Ops);
|
|
return 0;
|
|
}
|
|
|
|
|
|
/// ReassociateBB - Inspect all of the instructions in this basic block,
|
|
/// reassociating them as we go.
|
|
void Reassociate::ReassociateBB(BasicBlock *BB) {
|
|
for (BasicBlock::iterator BBI = BB->begin(); BBI != BB->end(); ) {
|
|
Instruction *BI = BBI++;
|
|
if (BI->getOpcode() == Instruction::Shl &&
|
|
isa<ConstantInt>(BI->getOperand(1)))
|
|
if (Instruction *NI = ConvertShiftToMul(BI)) {
|
|
MadeChange = true;
|
|
BI = NI;
|
|
}
|
|
|
|
// Reject cases where it is pointless to do this.
|
|
if (!isa<BinaryOperator>(BI) || BI->getType()->isFloatingPoint() ||
|
|
isa<VectorType>(BI->getType()))
|
|
continue; // Floating point ops are not associative.
|
|
|
|
// If this is a subtract instruction which is not already in negate form,
|
|
// see if we can convert it to X+-Y.
|
|
if (BI->getOpcode() == Instruction::Sub) {
|
|
if (ShouldBreakUpSubtract(BI)) {
|
|
BI = BreakUpSubtract(BI);
|
|
MadeChange = true;
|
|
} else if (BinaryOperator::isNeg(BI)) {
|
|
// 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(BI->getOperand(1), Instruction::Mul) &&
|
|
(!BI->hasOneUse() ||
|
|
!isReassociableOp(BI->use_back(), Instruction::Mul))) {
|
|
BI = LowerNegateToMultiply(BI);
|
|
MadeChange = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
// If this instruction is a commutative binary operator, process it.
|
|
if (!BI->isAssociative()) continue;
|
|
BinaryOperator *I = cast<BinaryOperator>(BI);
|
|
|
|
// 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.
|
|
if (I->hasOneUse() && isReassociableOp(I->use_back(), I->getOpcode()))
|
|
continue;
|
|
|
|
// If this is an add tree that is used by a sub instruction, ignore it
|
|
// until we process the subtract.
|
|
if (I->hasOneUse() && I->getOpcode() == Instruction::Add &&
|
|
cast<Instruction>(I->use_back())->getOpcode() == Instruction::Sub)
|
|
continue;
|
|
|
|
ReassociateExpression(I);
|
|
}
|
|
}
|
|
|
|
void Reassociate::ReassociateExpression(BinaryOperator *I) {
|
|
|
|
// First, walk the expression tree, linearizing the tree, collecting
|
|
std::vector<ValueEntry> Ops;
|
|
LinearizeExprTree(I, Ops);
|
|
|
|
DOUT << "RAIn:\t"; DEBUG(PrintOps(I, Ops)); DOUT << "\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)) {
|
|
// This expression tree simplified to something that isn't a tree,
|
|
// eliminate it.
|
|
DOUT << "Reassoc to scalar: " << *V << "\n";
|
|
I->replaceAllUsesWith(V);
|
|
RemoveDeadBinaryOp(I);
|
|
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->getOpcode() == Instruction::Mul && I->hasOneUse() &&
|
|
cast<Instruction>(I->use_back())->getOpcode() == Instruction::Add &&
|
|
isa<ConstantInt>(Ops.back().Op) &&
|
|
cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
|
|
Ops.insert(Ops.begin(), Ops.back());
|
|
Ops.pop_back();
|
|
}
|
|
|
|
DOUT << "RAOut:\t"; DEBUG(PrintOps(I, Ops)); DOUT << "\n";
|
|
|
|
if (Ops.size() == 1) {
|
|
// This expression tree simplified to something that isn't a tree,
|
|
// eliminate it.
|
|
I->replaceAllUsesWith(Ops[0].Op);
|
|
RemoveDeadBinaryOp(I);
|
|
} else {
|
|
// 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) {
|
|
// Recalculate the rank map for F
|
|
BuildRankMap(F);
|
|
|
|
MadeChange = false;
|
|
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
|
|
ReassociateBB(FI);
|
|
|
|
// We are done with the rank map...
|
|
RankMap.clear();
|
|
ValueRankMap.clear();
|
|
return MadeChange;
|
|
}
|
|
|