//===----------------------------------------------------------------------===//
//
// This pass reassociates commutative expressions in an order that is designed
-// to promote better constant propagation, GCSE, LICM, PRE...
+// to promote better constant propagation, GCSE, LICM, PRE, etc.
//
// For example: 4 + (x + 5) -> x + (4 + 5)
//
#define DEBUG_TYPE "reassociate"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Pass.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Assembly/Writer.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/Pass.h"
#include "llvm/Support/CFG.h"
-#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ValueHandle.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/ADT/PostOrderIterator.h"
-#include "llvm/ADT/Statistic.h"
+#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
-#include <map>
using namespace llvm;
-STATISTIC(NumLinear , "Number of insts linearized");
STATISTIC(NumChanged, "Number of insts reassociated");
STATISTIC(NumAnnihil, "Number of expr tree annihilated");
STATISTIC(NumFactor , "Number of multiplies factored");
namespace {
- struct VISIBILITY_HIDDEN ValueEntry {
+ struct ValueEntry {
unsigned Rank;
Value *Op;
ValueEntry(unsigned R, Value *O) : Rank(R), Op(O) {}
#ifndef NDEBUG
/// PrintOps - Print out the expression identified in the Ops list.
///
-static void PrintOps(Instruction *I, const std::vector<ValueEntry> &Ops) {
+static void PrintOps(Instruction *I, const SmallVectorImpl<ValueEntry> &Ops) {
Module *M = I->getParent()->getParent()->getParent();
- errs() << Instruction::getOpcodeName(I->getOpcode()) << " "
- << *Ops[0].Op->getType();
+ dbgs() << Instruction::getOpcodeName(I->getOpcode()) << " "
+ << *Ops[0].Op->getType() << '\t';
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
- WriteAsOperand(errs() << " ", Ops[i].Op, false, M);
- errs() << "," << Ops[i].Rank;
+ dbgs() << "[ ";
+ WriteAsOperand(dbgs(), Ops[i].Op, false, M);
+ dbgs() << ", #" << Ops[i].Rank << "] ";
}
}
#endif
-
+
namespace {
- class VISIBILITY_HIDDEN Reassociate : public FunctionPass {
- std::map<BasicBlock*, unsigned> RankMap;
- std::map<AssertingVH<>, unsigned> ValueRankMap;
+ /// \brief Utility class representing a base and exponent pair which form one
+ /// factor of some product.
+ struct Factor {
+ Value *Base;
+ unsigned Power;
+
+ Factor(Value *Base, unsigned Power) : Base(Base), Power(Power) {}
+
+ /// \brief Sort factors by their Base.
+ struct BaseSorter {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Base < RHS.Base;
+ }
+ };
+
+ /// \brief Compare factors for equal bases.
+ struct BaseEqual {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Base == RHS.Base;
+ }
+ };
+
+ /// \brief Sort factors in descending order by their power.
+ struct PowerDescendingSorter {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Power > RHS.Power;
+ }
+ };
+
+ /// \brief Compare factors for equal powers.
+ struct PowerEqual {
+ bool operator()(const Factor &LHS, const Factor &RHS) {
+ return LHS.Power == RHS.Power;
+ }
+ };
+ };
+}
+
+namespace {
+ class Reassociate : public FunctionPass {
+ DenseMap<BasicBlock*, unsigned> RankMap;
+ DenseMap<AssertingVH<Value>, unsigned> ValueRankMap;
+ SetVector<AssertingVH<Instruction> > RedoInsts;
bool MadeChange;
public:
static char ID; // Pass identification, replacement for typeid
- Reassociate() : FunctionPass(&ID) {}
+ Reassociate() : FunctionPass(ID) {
+ initializeReassociatePass(*PassRegistry::getPassRegistry());
+ }
bool runOnFunction(Function &F);
void BuildRankMap(Function &F);
unsigned getRank(Value *V);
void ReassociateExpression(BinaryOperator *I);
- void RewriteExprTree(BinaryOperator *I, std::vector<ValueEntry> &Ops,
- unsigned Idx = 0);
- Value *OptimizeExpression(BinaryOperator *I, std::vector<ValueEntry> &Ops);
- void LinearizeExprTree(BinaryOperator *I, std::vector<ValueEntry> &Ops);
- void LinearizeExpr(BinaryOperator *I);
+ void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
+ Value *OptimizeExpression(BinaryOperator *I,
+ SmallVectorImpl<ValueEntry> &Ops);
+ Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
+ bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
+ SmallVectorImpl<Factor> &Factors);
+ Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
+ SmallVectorImpl<Factor> &Factors);
+ Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
Value *RemoveFactorFromExpression(Value *V, Value *Factor);
- void ReassociateBB(BasicBlock *BB);
-
- void RemoveDeadBinaryOp(Value *V);
+ void EraseInst(Instruction *I);
+ void OptimizeInst(Instruction *I);
};
}
char Reassociate::ID = 0;
-static RegisterPass<Reassociate> X("reassociate", "Reassociate expressions");
+INITIALIZE_PASS(Reassociate, "reassociate",
+ "Reassociate expressions", false, false)
// Public interface to the Reassociate pass
FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
-void Reassociate::RemoveDeadBinaryOp(Value *V) {
- Instruction *Op = dyn_cast<Instruction>(V);
- if (!Op || !isa<BinaryOperator>(Op) || !isa<CmpInst>(Op) || !Op->use_empty())
- return;
-
- Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
- RemoveDeadBinaryOp(LHS);
- RemoveDeadBinaryOp(RHS);
+/// isReassociableOp - Return true if V is an instruction of the specified
+/// opcode and if it only has one use.
+static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
+ if (V->hasOneUse() && isa<Instruction>(V) &&
+ cast<Instruction>(V)->getOpcode() == Opcode)
+ return cast<BinaryOperator>(V);
+ return 0;
}
-
static bool isUnmovableInstruction(Instruction *I) {
if (I->getOpcode() == Instruction::PHI ||
+ I->getOpcode() == Instruction::LandingPad ||
I->getOpcode() == Instruction::Alloca ||
I->getOpcode() == Instruction::Load ||
- I->getOpcode() == Instruction::Malloc ||
I->getOpcode() == Instruction::Invoke ||
(I->getOpcode() == Instruction::Call &&
!isa<DbgInfoIntrinsic>(I)) ||
- I->getOpcode() == Instruction::UDiv ||
+ I->getOpcode() == Instruction::UDiv ||
I->getOpcode() == Instruction::SDiv ||
I->getOpcode() == Instruction::FDiv ||
I->getOpcode() == Instruction::URem ||
}
unsigned Reassociate::getRank(Value *V) {
- if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument...
-
Instruction *I = dyn_cast<Instruction>(V);
- if (I == 0) return 0; // Otherwise it's a global or constant, rank 0.
+ if (I == 0) {
+ if (isa<Argument>(V)) return ValueRankMap[V]; // Function argument.
+ return 0; // Otherwise it's a global or constant, rank 0.
+ }
- unsigned &CachedRank = ValueRankMap[I];
- if (CachedRank) return CachedRank; // Rank already known?
+ if (unsigned Rank = ValueRankMap[I])
+ return Rank; // Rank already known?
// If this is an expression, return the 1+MAX(rank(LHS), rank(RHS)) so that
// we can reassociate expressions for code motion! Since we do not recurse
// If this is a not or neg instruction, do not count it for rank. This
// assures us that X and ~X will have the same rank.
- if (!I->getType()->isInteger() ||
+ if (!I->getType()->isIntegerTy() ||
(!BinaryOperator::isNot(I) && !BinaryOperator::isNeg(I)))
++Rank;
- //DEBUG(errs() << "Calculated Rank[" << V->getName() << "] = "
+ //DEBUG(dbgs() << "Calculated Rank[" << V->getName() << "] = "
// << Rank << "\n");
- return CachedRank = Rank;
-}
-
-/// isReassociableOp - Return true if V is an instruction of the specified
-/// opcode and if it only has one use.
-static BinaryOperator *isReassociableOp(Value *V, unsigned Opcode) {
- if ((V->hasOneUse() || V->use_empty()) && isa<Instruction>(V) &&
- cast<Instruction>(V)->getOpcode() == Opcode)
- return cast<BinaryOperator>(V);
- return 0;
+ return ValueRankMap[I] = Rank;
}
/// LowerNegateToMultiply - Replace 0-X with X*-1.
///
-static Instruction *LowerNegateToMultiply(Instruction *Neg,
- std::map<AssertingVH<>, unsigned> &ValueRankMap,
- LLVMContext &Context) {
+static BinaryOperator *LowerNegateToMultiply(Instruction *Neg) {
Constant *Cst = Constant::getAllOnesValue(Neg->getType());
- Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
- ValueRankMap.erase(Neg);
+ BinaryOperator *Res =
+ BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
+ Neg->setOperand(1, Constant::getNullValue(Neg->getType())); // Drop use of op.
Res->takeName(Neg);
Neg->replaceAllUsesWith(Res);
- Neg->eraseFromParent();
+ Res->setDebugLoc(Neg->getDebugLoc());
return Res;
}
-// Given an expression of the form '(A+B)+(D+C)', turn it into '(((A+B)+C)+D)'.
-// Note that if D is also part of the expression tree that we recurse to
-// linearize it as well. Besides that case, this does not recurse into A,B, or
-// C.
-void Reassociate::LinearizeExpr(BinaryOperator *I) {
- BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
- BinaryOperator *RHS = cast<BinaryOperator>(I->getOperand(1));
- assert(isReassociableOp(LHS, I->getOpcode()) &&
- isReassociableOp(RHS, I->getOpcode()) &&
- "Not an expression that needs linearization?");
-
- DEBUG(errs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n');
-
- // Move the RHS instruction to live immediately before I, avoiding breaking
- // dominator properties.
- RHS->moveBefore(I);
-
- // Move operands around to do the linearization.
- I->setOperand(1, RHS->getOperand(0));
- RHS->setOperand(0, LHS);
- I->setOperand(0, RHS);
+/// CarmichaelShift - Returns k such that lambda(2^Bitwidth) = 2^k, where lambda
+/// is the Carmichael function. This means that x^(2^k) === 1 mod 2^Bitwidth for
+/// every odd x, i.e. x^(2^k) = 1 for every odd x in Bitwidth-bit arithmetic.
+/// Note that 0 <= k < Bitwidth, and if Bitwidth > 3 then x^(2^k) = 0 for every
+/// even x in Bitwidth-bit arithmetic.
+static unsigned CarmichaelShift(unsigned Bitwidth) {
+ if (Bitwidth < 3)
+ return Bitwidth - 1;
+ return Bitwidth - 2;
+}
- ++NumLinear;
- MadeChange = true;
- DEBUG(errs() << "Linearized: " << *I << '\n');
+/// IncorporateWeight - Add the extra weight 'RHS' to the existing weight 'LHS',
+/// reducing the combined weight using any special properties of the operation.
+/// The existing weight LHS represents the computation X op X op ... op X where
+/// X occurs LHS times. The combined weight represents X op X op ... op X with
+/// X occurring LHS + RHS times. If op is "Xor" for example then the combined
+/// operation is equivalent to X if LHS + RHS is odd, or 0 if LHS + RHS is even;
+/// the routine returns 1 in LHS in the first case, and 0 in LHS in the second.
+static void IncorporateWeight(APInt &LHS, const APInt &RHS, unsigned Opcode) {
+ // If we were working with infinite precision arithmetic then the combined
+ // weight would be LHS + RHS. But we are using finite precision arithmetic,
+ // and the APInt sum LHS + RHS may not be correct if it wraps (it is correct
+ // for nilpotent operations and addition, but not for idempotent operations
+ // and multiplication), so it is important to correctly reduce the combined
+ // weight back into range if wrapping would be wrong.
+
+ // If RHS is zero then the weight didn't change.
+ if (RHS.isMinValue())
+ return;
+ // If LHS is zero then the combined weight is RHS.
+ if (LHS.isMinValue()) {
+ LHS = RHS;
+ return;
+ }
+ // From this point on we know that neither LHS nor RHS is zero.
+
+ if (Instruction::isIdempotent(Opcode)) {
+ // Idempotent means X op X === X, so any non-zero weight is equivalent to a
+ // weight of 1. Keeping weights at zero or one also means that wrapping is
+ // not a problem.
+ assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
+ return; // Return a weight of 1.
+ }
+ if (Instruction::isNilpotent(Opcode)) {
+ // Nilpotent means X op X === 0, so reduce weights modulo 2.
+ assert(LHS == 1 && RHS == 1 && "Weights not reduced!");
+ LHS = 0; // 1 + 1 === 0 modulo 2.
+ return;
+ }
+ if (Opcode == Instruction::Add) {
+ // TODO: Reduce the weight by exploiting nsw/nuw?
+ LHS += RHS;
+ return;
+ }
- // If D is part of this expression tree, tail recurse.
- if (isReassociableOp(I->getOperand(1), I->getOpcode()))
- LinearizeExpr(I);
+ assert(Opcode == Instruction::Mul && "Unknown associative operation!");
+ unsigned Bitwidth = LHS.getBitWidth();
+ // If CM is the Carmichael number then a weight W satisfying W >= CM+Bitwidth
+ // can be replaced with W-CM. That's because x^W=x^(W-CM) for every Bitwidth
+ // bit number x, since either x is odd in which case x^CM = 1, or x is even in
+ // which case both x^W and x^(W - CM) are zero. By subtracting off multiples
+ // of CM like this weights can always be reduced to the range [0, CM+Bitwidth)
+ // which by a happy accident means that they can always be represented using
+ // Bitwidth bits.
+ // TODO: Reduce the weight by exploiting nsw/nuw? (Could do much better than
+ // the Carmichael number).
+ if (Bitwidth > 3) {
+ /// CM - The value of Carmichael's lambda function.
+ APInt CM = APInt::getOneBitSet(Bitwidth, CarmichaelShift(Bitwidth));
+ // Any weight W >= Threshold can be replaced with W - CM.
+ APInt Threshold = CM + Bitwidth;
+ assert(LHS.ult(Threshold) && RHS.ult(Threshold) && "Weights not reduced!");
+ // For Bitwidth 4 or more the following sum does not overflow.
+ LHS += RHS;
+ while (LHS.uge(Threshold))
+ LHS -= CM;
+ } else {
+ // To avoid problems with overflow do everything the same as above but using
+ // a larger type.
+ unsigned CM = 1U << CarmichaelShift(Bitwidth);
+ unsigned Threshold = CM + Bitwidth;
+ assert(LHS.getZExtValue() < Threshold && RHS.getZExtValue() < Threshold &&
+ "Weights not reduced!");
+ unsigned Total = LHS.getZExtValue() + RHS.getZExtValue();
+ while (Total >= Threshold)
+ Total -= CM;
+ LHS = Total;
+ }
}
-
-/// LinearizeExprTree - Given an associative binary expression tree, traverse
-/// all of the uses putting it into canonical form. This forces a left-linear
-/// form of the the expression (((a+b)+c)+d), and collects information about the
-/// rank of the non-tree operands.
+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:
///
-/// NOTE: These intentionally destroys the expression tree operands (turning
-/// them into undef values) to reduce #uses of the values. This means that the
-/// caller MUST use something like RewriteExprTree to put the values back in.
+/// + | I
+/// / \ |
+/// + + | A, B - operand of B replaced with undef
+/// / \ \ |
+/// * + * | C, D, E
+/// / \ / \ / \ |
+/// + * | F, G
///
-void Reassociate::LinearizeExprTree(BinaryOperator *I,
- std::vector<ValueEntry> &Ops) {
- Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
+/// 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();
- LLVMContext &Context = I->getContext();
-
- // First step, linearize the expression if it is in ((A+B)+(C+D)) form.
- BinaryOperator *LHSBO = isReassociableOp(LHS, Opcode);
- BinaryOperator *RHSBO = isReassociableOp(RHS, Opcode);
-
- // If this is a multiply expression tree and it contains internal negations,
- // transform them into multiplies by -1 so they can be reassociated.
- if (I->getOpcode() == Instruction::Mul) {
- if (!LHSBO && LHS->hasOneUse() && BinaryOperator::isNeg(LHS)) {
- LHS = LowerNegateToMultiply(cast<Instruction>(LHS),
- ValueRankMap, Context);
- LHSBO = isReassociableOp(LHS, Opcode);
- }
- if (!RHSBO && RHS->hasOneUse() && BinaryOperator::isNeg(RHS)) {
- RHS = LowerNegateToMultiply(cast<Instruction>(RHS),
- ValueRankMap, Context);
- RHSBO = isReassociableOp(RHS, Opcode);
- }
- }
+ assert(Instruction::isAssociative(Opcode) &&
+ Instruction::isCommutative(Opcode) &&
+ "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.
- if (!LHSBO) {
- if (!RHSBO) {
- // Neither the LHS or RHS as part of the tree, thus this is a leaf. As
- // such, just remember these operands and their rank.
- Ops.push_back(ValueEntry(getRank(LHS), LHS));
- Ops.push_back(ValueEntry(getRank(RHS), RHS));
-
- // Clear the leaves out.
- I->setOperand(0, UndefValue::get(I->getType()));
- I->setOperand(1, UndefValue::get(I->getType()));
- return;
- } else {
- // Turn X+(Y+Z) -> (Y+Z)+X
- std::swap(LHSBO, RHSBO);
- std::swap(LHS, RHS);
- bool Success = !I->swapOperands();
- assert(Success && "swapOperands failed");
- Success = false;
- MadeChange = true;
+#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.
+ BinaryOperator *BO = dyn_cast<BinaryOperator>(Op);
+ if (Opcode == Instruction::Mul && BO && BinaryOperator::isNeg(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;
}
- } else if (RHSBO) {
- // Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the the RHS is not
- // part of the expression tree.
- LinearizeExpr(I);
- LHS = LHSBO = cast<BinaryOperator>(I->getOperand(0));
- RHS = I->getOperand(1);
- RHSBO = 0;
}
- // Okay, now we know that the LHS is a nested expression and that the RHS is
- // not. Perform reassociation.
- assert(!isReassociableOp(RHS, Opcode) && "LinearizeExpr failed!");
-
- // Move LHS right before I to make sure that the tree expression dominates all
- // values.
- LHSBO->moveBefore(I);
+ // 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));
+ }
- // Linearize the expression tree on the LHS.
- LinearizeExprTree(LHSBO, Ops);
+ // 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)));
+ }
- // Remember the RHS operand and its rank.
- Ops.push_back(ValueEntry(getRank(RHS), RHS));
-
- // Clear the RHS leaf out.
- I->setOperand(1, UndefValue::get(I->getType()));
+ return MadeChange;
}
// RewriteExprTree - Now that the operands for this expression tree are
-// linearized and optimized, emit them in-order. This function is written to be
-// tail recursive.
+// linearized and optimized, emit them in-order.
void Reassociate::RewriteExprTree(BinaryOperator *I,
- std::vector<ValueEntry> &Ops,
- unsigned i) {
- if (i+2 == Ops.size()) {
- if (I->getOperand(0) != Ops[i].Op ||
- I->getOperand(1) != Ops[i+1].Op) {
- Value *OldLHS = I->getOperand(0);
- DEBUG(errs() << "RA: " << *I << '\n');
- I->setOperand(0, Ops[i].Op);
- I->setOperand(1, Ops[i+1].Op);
- DEBUG(errs() << "TO: " << *I << '\n');
+ 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 = 0;
+ 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;
-
- // If we reassociated a tree to fewer operands (e.g. (1+a+2) -> (a+3)
- // delete the extra, now dead, nodes.
- RemoveDeadBinaryOp(OldLHS);
+
+ break;
}
- return;
- }
- assert(i+2 < Ops.size() && "Ops index out of range!");
- if (I->getOperand(1) != Ops[i].Op) {
- DEBUG(errs() << "RA: " << *I << '\n');
- I->setOperand(1, Ops[i].Op);
- DEBUG(errs() << "TO: " << *I << '\n');
+ // 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);
+ } 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;
}
-
- BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
- assert(LHS->getOpcode() == I->getOpcode() &&
- "Improper expression tree!");
-
- // Compactify the tree instructions together with each other to guarantee
- // that the expression tree is dominated by all of Ops.
- LHS->moveBefore(I);
- RewriteExprTree(LHS, Ops, i+1);
-}
+ // 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 {
+ ExpressionChanged->clearSubclassOptionalData();
+ if (ExpressionChanged == I)
+ break;
+ ExpressionChanged->moveBefore(I);
+ ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->use_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 (Constant *C = dyn_cast<Constant>(V))
+ return ConstantExpr::getNeg(C);
-// 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(LLVMContext &Context, Value *V, Instruction *BI) {
// 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,
// 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...
+ // we introduce tons of unnecessary negation instructions.
//
- if (Instruction *I = dyn_cast<Instruction>(V))
- if (I->getOpcode() == Instruction::Add && I->hasOneUse()) {
- // Push the negates through the add.
- I->setOperand(0, NegateValue(Context, I->getOperand(0), BI));
- I->setOperand(1, NegateValue(Context, 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;
+ if (BinaryOperator *I = isReassociableOp(V, Instruction::Add)) {
+ // 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 (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){
+ User *U = *UI;
+ if (!BinaryOperator::isNeg(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 BinaryOperator::CreateNeg(V, V->getName() + ".neg", BI);
}
/// ShouldBreakUpSubtract - Return true if we should break up this subtract of
/// X-Y into (X + -Y).
-static bool ShouldBreakUpSubtract(LLVMContext &Context, Instruction *Sub) {
+static bool ShouldBreakUpSubtract(Instruction *Sub) {
// If this is a negation, we can't split it up!
if (BinaryOperator::isNeg(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.
if (isReassociableOp(Sub->getOperand(0), Instruction::Add) ||
if (isReassociableOp(Sub->getOperand(1), Instruction::Add) ||
isReassociableOp(Sub->getOperand(1), Instruction::Sub))
return true;
- if (Sub->hasOneUse() &&
+ if (Sub->hasOneUse() &&
(isReassociableOp(Sub->use_back(), Instruction::Add) ||
isReassociableOp(Sub->use_back(), Instruction::Sub)))
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 Instruction *BreakUpSubtract(LLVMContext &Context, Instruction *Sub,
- std::map<AssertingVH<>, unsigned> &ValueRankMap) {
- // Convert a subtract into an add and a neg instruction... so that sub
- // instructions can be commuted with other add instructions...
+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...
+ // 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(Context, Sub->getOperand(1), Sub);
- Instruction *New =
+ Value *NegVal = NegateValue(Sub->getOperand(1), Sub);
+ BinaryOperator *New =
BinaryOperator::CreateAdd(Sub->getOperand(0), NegVal, "", 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.
- ValueRankMap.erase(Sub);
Sub->replaceAllUsesWith(New);
- Sub->eraseFromParent();
+ New->setDebugLoc(Sub->getDebugLoc());
- DEBUG(errs() << "Negated: " << *New << '\n');
+ 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 Instruction *ConvertShiftToMul(Instruction *Shl,
- std::map<AssertingVH<>, unsigned> &ValueRankMap,
- LLVMContext &Context) {
- // 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(Shl->getOperand(0), Instruction::Mul) ||
- (Shl->hasOneUse() &&
- (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);
- ValueRankMap.erase(Shl);
- Mul->takeName(Shl);
- Shl->replaceAllUsesWith(Mul);
- Shl->eraseFromParent();
- return Mul;
- }
- return 0;
+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;
}
-// 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,
+/// 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
+ // Scan backwards.
for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j)
if (Ops[j].Op == X)
return j;
/// 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) {
+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 BinaryOperator::CreateAdd(V2, V1, "tmp", I);
}
-/// RemoveFactorFromExpression - If V is an expression tree that is a
+/// 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);
+
+ 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;
- for (unsigned i = 0, e = Factors.size(); i != e; ++i)
+ 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;
+ }
+ }
+
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;
+
+ 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 = BinaryOperator::CreateNeg(V, "neg", InsertPt);
+
+ 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,
- std::vector<Value*> &Factors) {
- BinaryOperator *BO;
- if ((!V->hasOneUse() && !V->use_empty()) ||
- !(BO = dyn_cast<BinaryOperator>(V)) ||
- BO->getOpcode() != Instruction::Mul) {
+ SmallVectorImpl<Value*> &Factors,
+ const SmallVectorImpl<ValueEntry> &Ops) {
+ BinaryOperator *BO = isReassociableOp(V, Instruction::Mul);
+ if (!BO) {
Factors.push_back(V);
return;
}
-
+
// Otherwise, add the LHS and RHS to the list of factors.
- FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
- FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
+ 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;
+ }
-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;
+ // Drop pairs of values for Xor.
+ assert(Opcode == Instruction::Xor);
+ if (e == 2)
+ return Constant::getNullValue(Ops[0].Op->getType());
- 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);
+ // Y ^ X^X -> Y
+ Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
+ i -= 1; e -= 2;
+ ++NumAnnihil;
}
+ }
+ return 0;
+}
- // 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;
+/// 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 the expression. X+-X == 0. While we're at it, scan for any
+ // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
+ //
+ // TODO: We could handle "X + ~X" -> "-1" if we wanted, since "-X = ~X+1".
+ //
+ 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.
+ Value *Mul = ConstantInt::get(cast<IntegerType>(I->getType()), NumFound);
+ Mul = BinaryOperator::CreateMul(TheOp, Mul, "factor", 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(cast<Instruction>(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 in the operand list.
+ if (!BinaryOperator::isNeg(TheOp))
+ continue;
+
+ Value *X = BinaryOperator::getNegArgument(TheOp);
+ unsigned FoundX = FindInOperandList(Ops, i, X);
+ if (FoundX == i)
+ continue;
+
+ // Remove X and -X from the operand list.
+ if (Ops.size() == 2)
+ return Constant::getNullValue(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.
+ }
+
+ // 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 = 0;
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+ BinaryOperator *BOp = isReassociableOp(Ops[i].Op, Instruction::Mul);
+ 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; }
+ }
+ }
+ }
+
+ // 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 = BinaryOperator::CreateAdd(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);
+ 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;
}
- // FALLTHROUGH!
- case Instruction::Add:
- case Instruction::Xor:
- if (CstVal->isZero()) // ... [|^+] 0 -> ...
- Ops.pop_back();
- break;
}
+
+ // 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 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", 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 0;
+}
+
+namespace {
+ /// \brief Predicate tests whether a ValueEntry's op is in a map.
+ struct IsValueInMap {
+ const DenseMap<Value *, unsigned> ⤅
+
+ IsValueInMap(const DenseMap<Value *, unsigned> &Map) : Map(Map) {}
+
+ bool operator()(const ValueEntry &Entry) {
+ return Map.find(Entry.Op) != Map.end();
+ }
+ };
+}
+
+/// \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::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 {
+ LHS = Builder.CreateMul(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 0;
+
+ // 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 0; // 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 0;
+}
+
+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 = 0;
+ 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 do to identities between elements in the
+ // 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:
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 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.
- 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;
- }
- }
- }
+ if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
+ return Result;
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 (Value *Result = OptimizeAdd(I, Ops))
+ return Result;
+ break;
- // If any factor occurred more than one time, we can pull it out.
- if (MaxOcc > 1) {
- DEBUG(errs() << "\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);
- }
+ case Instruction::Mul:
+ if (Value *Result = OptimizeMul(I, Ops))
+ return Result;
break;
- //case Instruction::Mul:
}
- if (IterateOptimization)
+ if (Ops.size() != NumOps)
return OptimizeExpression(I, Ops);
return 0;
}
+/// 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->use_back()->getOpcode() == Opcode &&
+ Visited.insert(Op))
+ Op = Op->use_back();
+ RedoInsts.insert(Op);
+ }
+}
-/// ReassociateBB - Inspect all of the instructions in this basic block,
-/// reassociating them as we go.
-void Reassociate::ReassociateBB(BasicBlock *BB) {
- LLVMContext &Context = BB->getContext();
-
- 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, ValueRankMap, Context)) {
- MadeChange = true;
- BI = NI;
- }
+/// 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;
- // 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 (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->use_back(), Instruction::Mul) ||
+ isReassociableOp(I->use_back(), Instruction::Add)))) {
+ Instruction *NI = ConvertShiftToMul(I);
+ RedoInsts.insert(I);
+ MadeChange = true;
+ I = NI;
+ }
+
+ // Floating point binary operators are not associative, but we can still
+ // commute (some) of them, 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.
+ if (I->getOpcode() != Instruction::FMul &&
+ I->getOpcode() != Instruction::FAdd)
+ return;
+
+ 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);
+ }
+
+ 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 (BI->getOpcode() == Instruction::Sub) {
- if (ShouldBreakUpSubtract(Context, BI)) {
- BI = BreakUpSubtract(Context, BI, ValueRankMap);
+ // 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->use_back(), Instruction::Mul))) {
+ Instruction *NI = LowerNegateToMultiply(I);
+ RedoInsts.insert(I);
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, ValueRankMap, Context);
- MadeChange = true;
- }
+ I = NI;
}
}
+ }
- // If this instruction is a commutative binary operator, process it.
- if (!BI->isAssociative()) continue;
- BinaryOperator *I = cast<BinaryOperator>(BI);
+ // 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.
- if (I->hasOneUse() && isReassociableOp(I->use_back(), I->getOpcode()))
- continue;
+ // 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->use_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 (I->hasOneUse() && I->getOpcode() == Instruction::Add &&
- cast<Instruction>(I->use_back())->getOpcode() == Instruction::Sub)
- continue;
+ // 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->use_back())->getOpcode() == Instruction::Sub)
+ return;
- ReassociateExpression(I);
- }
+ ReassociateExpression(BO);
}
void Reassociate::ReassociateExpression(BinaryOperator *I) {
-
- // First, walk the expression tree, linearizing the tree, collecting
- std::vector<ValueEntry> Ops;
- LinearizeExprTree(I, Ops);
-
- DEBUG(errs() << "RAIn:\t"; PrintOps(I, Ops); errs() << "\n");
-
+
+ // 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
// 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(errs() << "Reassoc to scalar: " << *V << "\n");
+ DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
I->replaceAllUsesWith(V);
- RemoveDeadBinaryOp(I);
+ 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
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();
+ ValueEntry Tmp = Ops.pop_back_val();
+ Ops.insert(Ops.begin(), Tmp);
}
-
- DEBUG(errs() << "RAOut:\t"; PrintOps(I, Ops); errs() << "\n");
-
+
+ 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);
- 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);
+ 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) {
- // Recalculate the rank map for F
+ // Calculate the rank map for F
BuildRankMap(F);
MadeChange = false;
- for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
- ReassociateBB(FI);
+ 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;
+ }
- // We are done with the rank map...
+ // 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;
}
-
projects / oota-llvm.git / blobdiff