#define DEBUG_TYPE "reassociate"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/Pass.h"
-#include "llvm/Assembly/Writer.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/IRBuilder.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/ValueHandle.h"
-#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PostOrderIterator.h"
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallMap.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/CFG.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/IR/ValueHandle.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/Local.h"
#include <algorithm>
using namespace llvm;
<< *Ops[0].Op->getType() << '\t';
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
dbgs() << "[ ";
- WriteAsOperand(dbgs(), Ops[i].Op, false, M);
+ Ops[i].Op->printAsOperand(dbgs(), false, M);
dbgs() << ", #" << Ops[i].Rank << "] ";
}
}
}
};
};
+
+ /// Utility class representing a non-constant Xor-operand. We classify
+ /// non-constant Xor-Operands into two categories:
+ /// C1) The operand is in the form "X & C", where C is a constant and C != ~0
+ /// C2)
+ /// C2.1) The operand is in the form of "X | C", where C is a non-zero
+ /// constant.
+ /// C2.2) Any operand E which doesn't fall into C1 and C2.1, we view this
+ /// operand as "E | 0"
+ class XorOpnd {
+ public:
+ XorOpnd(Value *V);
+
+ bool isInvalid() const { return SymbolicPart == 0; }
+ bool isOrExpr() const { return isOr; }
+ Value *getValue() const { return OrigVal; }
+ Value *getSymbolicPart() const { return SymbolicPart; }
+ unsigned getSymbolicRank() const { return SymbolicRank; }
+ const APInt &getConstPart() const { return ConstPart; }
+
+ void Invalidate() { SymbolicPart = OrigVal = 0; }
+ void setSymbolicRank(unsigned R) { SymbolicRank = R; }
+
+ // Sort the XorOpnd-Pointer in ascending order of symbolic-value-rank.
+ // The purpose is twofold:
+ // 1) Cluster together the operands sharing the same symbolic-value.
+ // 2) Operand having smaller symbolic-value-rank is permuted earlier, which
+ // could potentially shorten crital path, and expose more loop-invariants.
+ // Note that values' rank are basically defined in RPO order (FIXME).
+ // So, if Rank(X) < Rank(Y) < Rank(Z), it means X is defined earlier
+ // than Y which is defined earlier than Z. Permute "x | 1", "Y & 2",
+ // "z" in the order of X-Y-Z is better than any other orders.
+ struct PtrSortFunctor {
+ bool operator()(XorOpnd * const &LHS, XorOpnd * const &RHS) {
+ return LHS->getSymbolicRank() < RHS->getSymbolicRank();
+ }
+ };
+ private:
+ Value *OrigVal;
+ Value *SymbolicPart;
+ APInt ConstPart;
+ unsigned SymbolicRank;
+ bool isOr;
+ };
}
namespace {
initializeReassociatePass(*PassRegistry::getPassRegistry());
}
- bool runOnFunction(Function &F);
+ bool runOnFunction(Function &F) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
}
private:
void BuildRankMap(Function &F);
unsigned getRank(Value *V);
- Value *ReassociateExpression(BinaryOperator *I);
+ void ReassociateExpression(BinaryOperator *I);
void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
Value *OptimizeExpression(BinaryOperator *I,
SmallVectorImpl<ValueEntry> &Ops);
Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
+ Value *OptimizeXor(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
+ bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, APInt &ConstOpnd,
+ Value *&Res);
+ bool CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
+ APInt &ConstOpnd, Value *&Res);
bool collectMultiplyFactors(SmallVectorImpl<ValueEntry> &Ops,
SmallVectorImpl<Factor> &Factors);
Value *buildMinimalMultiplyDAG(IRBuilder<> &Builder,
SmallVectorImpl<Factor> &Factors);
Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
- void LinearizeExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
Value *RemoveFactorFromExpression(Value *V, Value *Factor);
void EraseInst(Instruction *I);
void OptimizeInst(Instruction *I);
};
}
+XorOpnd::XorOpnd(Value *V) {
+ assert(!isa<ConstantInt>(V) && "No ConstantInt");
+ OrigVal = V;
+ Instruction *I = dyn_cast<Instruction>(V);
+ SymbolicRank = 0;
+
+ if (I && (I->getOpcode() == Instruction::Or ||
+ I->getOpcode() == Instruction::And)) {
+ Value *V0 = I->getOperand(0);
+ Value *V1 = I->getOperand(1);
+ if (isa<ConstantInt>(V0))
+ std::swap(V0, V1);
+
+ if (ConstantInt *C = dyn_cast<ConstantInt>(V1)) {
+ ConstPart = C->getValue();
+ SymbolicPart = V0;
+ isOr = (I->getOpcode() == Instruction::Or);
+ return;
+ }
+ }
+
+ // view the operand as "V | 0"
+ SymbolicPart = V;
+ ConstPart = APInt::getNullValue(V->getType()->getIntegerBitWidth());
+ isOr = true;
+}
+
char Reassociate::ID = 0;
INITIALIZE_PASS(Reassociate, "reassociate",
"Reassociate expressions", false, false)
}
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::Invoke ||
- (I->getOpcode() == Instruction::Call &&
- !isa<DbgInfoIntrinsic>(I)) ||
- I->getOpcode() == Instruction::UDiv ||
- I->getOpcode() == Instruction::SDiv ||
- I->getOpcode() == Instruction::FDiv ||
- I->getOpcode() == Instruction::URem ||
- I->getOpcode() == Instruction::SRem ||
- I->getOpcode() == Instruction::FRem)
+ switch (I->getOpcode()) {
+ case Instruction::PHI:
+ case Instruction::LandingPad:
+ case Instruction::Alloca:
+ case Instruction::Load:
+ case Instruction::Invoke:
+ case Instruction::UDiv:
+ case Instruction::SDiv:
+ case Instruction::FDiv:
+ case Instruction::URem:
+ case Instruction::SRem:
+ case Instruction::FRem:
return true;
- return false;
+ case Instruction::Call:
+ return !isa<DbgInfoIntrinsic>(I);
+ default:
+ return false;
+ }
}
void Reassociate::BuildRankMap(Function &F) {
return Res;
}
+/// 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;
+}
+
+/// 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;
+ }
+
+ 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;
+ }
+}
+
+typedef std::pair<Value*, APInt> RepeatedValue;
+
/// LinearizeExprTree - Given an associative binary expression, return the leaf
-/// nodes in Ops. The original expression is the same as Ops[0] op ... Ops[N].
-/// Note that a node may occur multiple times in Ops, but if so all occurrences
-/// are consecutive in the vector.
+/// 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
/// + * | F, G
///
/// The leaf nodes are C, E, F and G. The Ops array will contain (maybe not in
-/// that order) C, E, F, F, G, G.
+/// 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,
/// 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.
+/// 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:
/// of the expression) if it can turn them into binary operators of the right
/// type and thus make the expression bigger.
-void Reassociate::LinearizeExprTree(BinaryOperator *I,
- SmallVectorImpl<ValueEntry> &Ops) {
+static bool LinearizeExprTree(BinaryOperator *I,
+ SmallVectorImpl<RepeatedValue> &Ops) {
DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
+ unsigned Bitwidth = I->getType()->getScalarType()->getPrimitiveSizeInBits();
+ unsigned Opcode = I->getOpcode();
+ 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
// 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*, unsigned>, 8> Worklist; // (Op, Weight)
- Worklist.push_back(std::make_pair(I, 1));
- unsigned Opcode = I->getOpcode();
+ 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
// Leaves - Keeps track of the set of putative leaves as well as the number of
// paths to each leaf seen so far.
- typedef SmallMap<Value*, unsigned, 8> LeafMap;
+ typedef DenseMap<Value*, APInt> LeafMap;
LeafMap Leaves; // Leaf -> Total weight so far.
SmallVector<Value*, 8> LeafOrder; // Ensure deterministic leaf output order.
SmallPtrSet<Value*, 8> Visited; // For sanity checking the iteration scheme.
#endif
while (!Worklist.empty()) {
- std::pair<BinaryOperator*, unsigned> P = Worklist.pop_back_val();
+ std::pair<BinaryOperator*, APInt> P = Worklist.pop_back_val();
I = P.first; // We examine the operands of this binary operator.
- assert(P.second >= 1 && "No paths to here, so how did we get here?!");
for (unsigned OpIdx = 0; OpIdx < 2; ++OpIdx) { // Visit operands.
Value *Op = I->getOperand(OpIdx);
- unsigned Weight = P.second; // Number of paths to this operand.
+ 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?!");
assert(Visited.count(Op) && "In leaf map but not visited!");
// Update the number of paths to the leaf.
- It->second += Weight;
+ 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!");
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.
Value *V = LeafOrder[i];
LeafMap::iterator It = Leaves.find(V);
if (It == Leaves.end())
- // Leaf already output, or node initially thought to be a leaf wasn't.
+ // Node initially thought to be a leaf wasn't.
continue;
assert(!isReassociableOp(V, Opcode) && "Shouldn't be a leaf!");
- unsigned Weight = It->second;
- assert(Weight > 0 && "No paths to this value!");
- // FIXME: Rather than repeating values Weight times, use a vector of
- // (ValueEntry, multiplicity) pairs.
- Ops.append(Weight, ValueEntry(getRank(V), V));
+ APInt Weight = It->second;
+ if (Weight.isMinValue())
+ // Leaf already output or weight reduction eliminated it.
+ continue;
// Ensure the leaf is only output once.
- Leaves.erase(It);
+ It->second = 0;
+ Ops.push_back(std::make_pair(V, Weight));
+ }
+
+ // For nilpotent operations or addition there may be no operands, for example
+ // because the expression was "X xor X" or consisted of 2^Bitwidth additions:
+ // in both cases the weight reduces to 0 causing the value to be skipped.
+ if (Ops.empty()) {
+ Constant *Identity = ConstantExpr::getBinOpIdentity(Opcode, I->getType());
+ assert(Identity && "Associative operation without identity!");
+ Ops.push_back(std::make_pair(Identity, APInt(Bitwidth, 1)));
}
+
+ return MadeChange;
}
// RewriteExprTree - Now that the operands for this expression tree are
SmallVectorImpl<ValueEntry> &Ops) {
assert(Ops.size() > 1 && "Single values should be used directly!");
- // Since our optimizations never increase the number of operations, the new
- // expression can always be written by reusing the existing binary operators
+ // 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
/// the new expression into.
SmallVector<BinaryOperator*, 8> NodesToRewrite;
unsigned Opcode = I->getOpcode();
- NodesToRewrite.push_back(I);
+ 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;
- BinaryOperator *Previous;
- BinaryOperator *Op = 0;
- for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
- assert(!NodesToRewrite.empty() &&
- "Optimized expressions has more nodes than original!");
- Previous = Op; Op = NodesToRewrite.pop_back_val();
- if (ExpressionChanged)
- // Compactify the tree instructions together with each other to guarantee
- // that the expression tree is dominated by all of Ops.
- Op->moveBefore(Previous);
-
+ 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.
// the old operands with the new ones.
DEBUG(dbgs() << "RA: " << *Op << '\n');
if (NewLHS != OldLHS) {
- if (BinaryOperator *BO = isReassociableOp(OldLHS, Opcode))
+ BinaryOperator *BO = isReassociableOp(OldLHS, Opcode);
+ if (BO && !NotRewritable.count(BO))
NodesToRewrite.push_back(BO);
Op->setOperand(0, NewLHS);
}
if (NewRHS != OldRHS) {
- if (BinaryOperator *BO = isReassociableOp(OldRHS, Opcode))
+ BinaryOperator *BO = isReassociableOp(OldRHS, Opcode);
+ if (BO && !NotRewritable.count(BO))
NodesToRewrite.push_back(BO);
Op->setOperand(1, NewRHS);
}
Op->swapOperands();
} else {
// Overwrite with the new right-hand side.
- if (BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode))
+ BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode);
+ if (BO && !NotRewritable.count(BO))
NodesToRewrite.push_back(BO);
Op->setOperand(1, NewRHS);
ExpressionChanged = Op;
// 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.
- if (BinaryOperator *BO = isReassociableOp(Op->getOperand(0), Opcode)) {
- NodesToRewrite.push_back(BO);
+ 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.
- assert(!NodesToRewrite.empty() &&
- "Optimized expressions has more nodes than original!");
+ // 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, NodesToRewrite.back());
+ Op->setOperand(0, NewOp);
DEBUG(dbgs() << "TO: " << *Op << '\n');
ExpressionChanged = Op;
MadeChange = true;
++NumChanged;
+ Op = NewOp;
}
// If the expression changed non-trivially then clear out all subclass data
- // starting from the operator specified in ExpressionChanged.
- if (ExpressionChanged) {
+ // 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 = cast<BinaryOperator>(*ExpressionChanged->use_begin());
+ ExpressionChanged->moveBefore(I);
+ ExpressionChanged = cast<BinaryOperator>(*ExpressionChanged->user_begin());
} while (1);
- }
// Throw away any left over nodes from the original expression.
for (unsigned i = 0, e = NodesToRewrite.size(); i != e; ++i)
// 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;
+ for (User *U : V->users()) {
if (!BinaryOperator::isNeg(U)) continue;
// We found one! Now we have to make sure that the definition dominates
isReassociableOp(Sub->getOperand(1), Instruction::Sub))
return true;
if (Sub->hasOneUse() &&
- (isReassociableOp(Sub->use_back(), Instruction::Add) ||
- isReassociableOp(Sub->use_back(), Instruction::Sub)))
+ (isReassociableOp(Sub->user_back(), Instruction::Add) ||
+ isReassociableOp(Sub->user_back(), Instruction::Sub)))
return true;
return false;
BinaryOperator *BO = isReassociableOp(V, Instruction::Mul);
if (!BO) return 0;
+ SmallVector<RepeatedValue, 8> Tree;
+ MadeChange |= LinearizeExprTree(BO, Tree);
SmallVector<ValueEntry, 8> Factors;
- LinearizeExprTree(BO, Factors);
+ Factors.reserve(Tree.size());
+ for (unsigned i = 0, e = Tree.size(); i != e; ++i) {
+ RepeatedValue E = Tree[i];
+ Factors.append(E.second.getZExtValue(),
+ ValueEntry(getRank(E.first), E.first));
+ }
bool FoundFactor = false;
bool NeedsNegate = false;
return 0;
}
+/// Helper funciton of CombineXorOpnd(). It creates a bitwise-and
+/// instruction with the given two operands, and return the resulting
+/// instruction. There are two special cases: 1) if the constant operand is 0,
+/// it will return NULL. 2) if the constant is ~0, the symbolic operand will
+/// be returned.
+static Value *createAndInstr(Instruction *InsertBefore, Value *Opnd,
+ const APInt &ConstOpnd) {
+ if (ConstOpnd != 0) {
+ if (!ConstOpnd.isAllOnesValue()) {
+ LLVMContext &Ctx = Opnd->getType()->getContext();
+ Instruction *I;
+ I = BinaryOperator::CreateAnd(Opnd, ConstantInt::get(Ctx, ConstOpnd),
+ "and.ra", InsertBefore);
+ I->setDebugLoc(InsertBefore->getDebugLoc());
+ return I;
+ }
+ return Opnd;
+ }
+ return 0;
+}
+
+// Helper function of OptimizeXor(). It tries to simplify "Opnd1 ^ ConstOpnd"
+// into "R ^ C", where C would be 0, and R is a symbolic value.
+//
+// If it was successful, true is returned, and the "R" and "C" is returned
+// via "Res" and "ConstOpnd", respectively; otherwise, false is returned,
+// and both "Res" and "ConstOpnd" remain unchanged.
+//
+bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1,
+ APInt &ConstOpnd, Value *&Res) {
+ // Xor-Rule 1: (x | c1) ^ c2 = (x | c1) ^ (c1 ^ c1) ^ c2
+ // = ((x | c1) ^ c1) ^ (c1 ^ c2)
+ // = (x & ~c1) ^ (c1 ^ c2)
+ // It is useful only when c1 == c2.
+ if (Opnd1->isOrExpr() && Opnd1->getConstPart() != 0) {
+ if (!Opnd1->getValue()->hasOneUse())
+ return false;
+
+ const APInt &C1 = Opnd1->getConstPart();
+ if (C1 != ConstOpnd)
+ return false;
+
+ Value *X = Opnd1->getSymbolicPart();
+ Res = createAndInstr(I, X, ~C1);
+ // ConstOpnd was C2, now C1 ^ C2.
+ ConstOpnd ^= C1;
+
+ if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
+ RedoInsts.insert(T);
+ return true;
+ }
+ return false;
+}
+
+
+// Helper function of OptimizeXor(). It tries to simplify
+// "Opnd1 ^ Opnd2 ^ ConstOpnd" into "R ^ C", where C would be 0, and R is a
+// symbolic value.
+//
+// If it was successful, true is returned, and the "R" and "C" is returned
+// via "Res" and "ConstOpnd", respectively (If the entire expression is
+// evaluated to a constant, the Res is set to NULL); otherwise, false is
+// returned, and both "Res" and "ConstOpnd" remain unchanged.
+bool Reassociate::CombineXorOpnd(Instruction *I, XorOpnd *Opnd1, XorOpnd *Opnd2,
+ APInt &ConstOpnd, Value *&Res) {
+ Value *X = Opnd1->getSymbolicPart();
+ if (X != Opnd2->getSymbolicPart())
+ return false;
+
+ // This many instruction become dead.(At least "Opnd1 ^ Opnd2" will die.)
+ int DeadInstNum = 1;
+ if (Opnd1->getValue()->hasOneUse())
+ DeadInstNum++;
+ if (Opnd2->getValue()->hasOneUse())
+ DeadInstNum++;
+
+ // Xor-Rule 2:
+ // (x | c1) ^ (x & c2)
+ // = (x|c1) ^ (x&c2) ^ (c1 ^ c1) = ((x|c1) ^ c1) ^ (x & c2) ^ c1
+ // = (x & ~c1) ^ (x & c2) ^ c1 // Xor-Rule 1
+ // = (x & c3) ^ c1, where c3 = ~c1 ^ c2 // Xor-rule 3
+ //
+ if (Opnd1->isOrExpr() != Opnd2->isOrExpr()) {
+ if (Opnd2->isOrExpr())
+ std::swap(Opnd1, Opnd2);
+
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3((~C1) ^ C2);
+
+ // Do not increase code size!
+ if (C3 != 0 && !C3.isAllOnesValue()) {
+ int NewInstNum = ConstOpnd != 0 ? 1 : 2;
+ if (NewInstNum > DeadInstNum)
+ return false;
+ }
+
+ Res = createAndInstr(I, X, C3);
+ ConstOpnd ^= C1;
+
+ } else if (Opnd1->isOrExpr()) {
+ // Xor-Rule 3: (x | c1) ^ (x | c2) = (x & c3) ^ c3 where c3 = c1 ^ c2
+ //
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3 = C1 ^ C2;
+
+ // Do not increase code size
+ if (C3 != 0 && !C3.isAllOnesValue()) {
+ int NewInstNum = ConstOpnd != 0 ? 1 : 2;
+ if (NewInstNum > DeadInstNum)
+ return false;
+ }
+
+ Res = createAndInstr(I, X, C3);
+ ConstOpnd ^= C3;
+ } else {
+ // Xor-Rule 4: (x & c1) ^ (x & c2) = (x & (c1^c2))
+ //
+ const APInt &C1 = Opnd1->getConstPart();
+ const APInt &C2 = Opnd2->getConstPart();
+ APInt C3 = C1 ^ C2;
+ Res = createAndInstr(I, X, C3);
+ }
+
+ // Put the original operands in the Redo list; hope they will be deleted
+ // as dead code.
+ if (Instruction *T = dyn_cast<Instruction>(Opnd1->getValue()))
+ RedoInsts.insert(T);
+ if (Instruction *T = dyn_cast<Instruction>(Opnd2->getValue()))
+ RedoInsts.insert(T);
+
+ return true;
+}
+
+/// Optimize a series of operands to an 'xor' instruction. If it can be reduced
+/// to a single Value, it is returned, otherwise the Ops list is mutated as
+/// necessary.
+Value *Reassociate::OptimizeXor(Instruction *I,
+ SmallVectorImpl<ValueEntry> &Ops) {
+ if (Value *V = OptimizeAndOrXor(Instruction::Xor, Ops))
+ return V;
+
+ if (Ops.size() == 1)
+ return 0;
+
+ SmallVector<XorOpnd, 8> Opnds;
+ SmallVector<XorOpnd*, 8> OpndPtrs;
+ Type *Ty = Ops[0].Op->getType();
+ APInt ConstOpnd(Ty->getIntegerBitWidth(), 0);
+
+ // Step 1: Convert ValueEntry to XorOpnd
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
+ Value *V = Ops[i].Op;
+ if (!isa<ConstantInt>(V)) {
+ XorOpnd O(V);
+ O.setSymbolicRank(getRank(O.getSymbolicPart()));
+ Opnds.push_back(O);
+ } else
+ ConstOpnd ^= cast<ConstantInt>(V)->getValue();
+ }
+
+ // NOTE: From this point on, do *NOT* add/delete element to/from "Opnds".
+ // It would otherwise invalidate the "Opnds"'s iterator, and hence invalidate
+ // the "OpndPtrs" as well. For the similar reason, do not fuse this loop
+ // with the previous loop --- the iterator of the "Opnds" may be invalidated
+ // when new elements are added to the vector.
+ for (unsigned i = 0, e = Opnds.size(); i != e; ++i)
+ OpndPtrs.push_back(&Opnds[i]);
+
+ // Step 2: Sort the Xor-Operands in a way such that the operands containing
+ // the same symbolic value cluster together. For instance, the input operand
+ // sequence ("x | 123", "y & 456", "x & 789") will be sorted into:
+ // ("x | 123", "x & 789", "y & 456").
+ std::stable_sort(OpndPtrs.begin(), OpndPtrs.end(), XorOpnd::PtrSortFunctor());
+
+ // Step 3: Combine adjacent operands
+ XorOpnd *PrevOpnd = 0;
+ bool Changed = false;
+ for (unsigned i = 0, e = Opnds.size(); i < e; i++) {
+ XorOpnd *CurrOpnd = OpndPtrs[i];
+ // The combined value
+ Value *CV;
+
+ // Step 3.1: Try simplifying "CurrOpnd ^ ConstOpnd"
+ if (ConstOpnd != 0 && CombineXorOpnd(I, CurrOpnd, ConstOpnd, CV)) {
+ Changed = true;
+ if (CV)
+ *CurrOpnd = XorOpnd(CV);
+ else {
+ CurrOpnd->Invalidate();
+ continue;
+ }
+ }
+
+ if (!PrevOpnd || CurrOpnd->getSymbolicPart() != PrevOpnd->getSymbolicPart()) {
+ PrevOpnd = CurrOpnd;
+ continue;
+ }
+
+ // step 3.2: When previous and current operands share the same symbolic
+ // value, try to simplify "PrevOpnd ^ CurrOpnd ^ ConstOpnd"
+ //
+ if (CombineXorOpnd(I, CurrOpnd, PrevOpnd, ConstOpnd, CV)) {
+ // Remove previous operand
+ PrevOpnd->Invalidate();
+ if (CV) {
+ *CurrOpnd = XorOpnd(CV);
+ PrevOpnd = CurrOpnd;
+ } else {
+ CurrOpnd->Invalidate();
+ PrevOpnd = 0;
+ }
+ Changed = true;
+ }
+ }
+
+ // Step 4: Reassemble the Ops
+ if (Changed) {
+ Ops.clear();
+ for (unsigned int i = 0, e = Opnds.size(); i < e; i++) {
+ XorOpnd &O = Opnds[i];
+ if (O.isInvalid())
+ continue;
+ ValueEntry VE(getRank(O.getValue()), O.getValue());
+ Ops.push_back(VE);
+ }
+ if (ConstOpnd != 0) {
+ Value *C = ConstantInt::get(Ty->getContext(), ConstOpnd);
+ ValueEntry VE(getRank(C), C);
+ Ops.push_back(VE);
+ }
+ int Sz = Ops.size();
+ if (Sz == 1)
+ return Ops.back().Op;
+ else if (Sz == 0) {
+ assert(ConstOpnd == 0);
+ return ConstantInt::get(Ty->getContext(), ConstOpnd);
+ }
+ }
+
+ return 0;
+}
+
/// 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.
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
// below our mininum of '4'.
assert(FactorPowerSum >= 4);
- std::sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
+ std::stable_sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
return true;
}
SmallVectorImpl<ValueEntry> &Ops) {
// Now that we have the linearized expression tree, try to optimize it.
// Start by folding any constants that we found.
- if (Ops.size() == 1) return Ops[0].Op;
-
+ 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 (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()) // X & 0 -> 0
- return CstVal;
- if (CstVal->isAllOnesValue()) // X & -1 -> X
- Ops.pop_back();
- break;
- case Instruction::Mul:
- if (CstVal->isZero()) { // X * 0 -> 0
- ++NumAnnihil;
- return CstVal;
- }
-
- if (cast<ConstantInt>(CstVal)->isOne())
- Ops.pop_back(); // X * 1 -> X
- break;
- case Instruction::Or:
- if (CstVal->isAllOnesValue()) // X | -1 -> -1
- return CstVal;
- // FALLTHROUGH!
- case Instruction::Add:
- case Instruction::Xor:
- if (CstVal->isZero()) // X [|^+] 0 -> X
- Ops.pop_back();
- break;
- }
if (Ops.size() == 1) return Ops[0].Op;
// Handle destructive annihilation due to identities between elements in the
default: break;
case Instruction::And:
case Instruction::Or:
- case Instruction::Xor:
if (Value *Result = OptimizeAndOrXor(Opcode, Ops))
return Result;
break;
+ case Instruction::Xor:
+ if (Value *Result = OptimizeXor(I, Ops))
+ return Result;
+ break;
+
case Instruction::Add:
if (Value *Result = OptimizeAdd(I, Ops))
return Result;
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)
- Op = Op->use_back();
+ while (Op->hasOneUse() && Op->user_back()->getOpcode() == Opcode &&
+ Visited.insert(Op))
+ Op = Op->user_back();
RedoInsts.insert(Op);
}
}
// 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)))) {
+ (isReassociableOp(I->user_back(), Instruction::Mul) ||
+ isReassociableOp(I->user_back(), Instruction::Add)))) {
Instruction *NI = ConvertShiftToMul(I);
RedoInsts.insert(I);
MadeChange = true;
// 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))) {
+ !isReassociableOp(I->user_back(), Instruction::Mul))) {
Instruction *NI = LowerNegateToMultiply(I);
RedoInsts.insert(I);
MadeChange = true;
// 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 (BO->hasOneUse() && BO->use_back()->getOpcode() == BO->getOpcode())
+ unsigned Opcode = BO->getOpcode();
+ if (BO->hasOneUse() && BO->user_back()->getOpcode() == Opcode)
return;
// If this is an add tree that is used by a sub instruction, ignore it
// until we process the subtract.
if (BO->hasOneUse() && BO->getOpcode() == Instruction::Add &&
- cast<Instruction>(BO->use_back())->getOpcode() == Instruction::Sub)
+ cast<Instruction>(BO->user_back())->getOpcode() == Instruction::Sub)
return;
ReassociateExpression(BO);
}
-Value *Reassociate::ReassociateExpression(BinaryOperator *I) {
+void Reassociate::ReassociateExpression(BinaryOperator *I) {
// First, walk the expression tree, linearizing the tree, collecting the
// operand information.
+ SmallVector<RepeatedValue, 8> Tree;
+ MadeChange |= LinearizeExprTree(I, Tree);
SmallVector<ValueEntry, 8> Ops;
- LinearizeExprTree(I, 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');
// OptimizeExpression - Now that we have the expression tree in a convenient
// sorted form, optimize it globally if possible.
if (Value *V = OptimizeExpression(I, Ops)) {
+ if (V == I)
+ // Self-referential expression in unreachable code.
+ return;
// This expression tree simplified to something that isn't a tree,
// eliminate it.
DEBUG(dbgs() << "Reassoc to scalar: " << *V << '\n');
VI->setDebugLoc(I->getDebugLoc());
RedoInsts.insert(I);
++NumAnnihil;
- return V;
+ return;
}
// We want to sink immediates as deeply as possible except in the case where
// 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 &&
+ cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
isa<ConstantInt>(Ops.back().Op) &&
cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
ValueEntry Tmp = Ops.pop_back_val();
DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
if (Ops.size() == 1) {
+ if (Ops[0].Op == I)
+ // Self-referential expression in unreachable code.
+ return;
+
// This expression tree simplified to something that isn't a tree,
// eliminate it.
I->replaceAllUsesWith(Ops[0].Op);
if (Instruction *OI = dyn_cast<Instruction>(Ops[0].Op))
OI->setDebugLoc(I->getDebugLoc());
RedoInsts.insert(I);
- return Ops[0].Op;
+ return;
}
// Now that we ordered and optimized the expressions, splat them back into
// the expression tree, removing any unneeded nodes.
RewriteExprTree(I, Ops);
- return I;
}
bool Reassociate::runOnFunction(Function &F) {
+ if (skipOptnoneFunction(F))
+ return false;
+
// Calculate the rank map for F
BuildRankMap(F);
projects / oota-llvm.git / blobdiff