#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/SmallMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/DenseMap.h"
#include <algorithm>
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");
}
}
#endif
-
+
namespace {
/// \brief Utility class representing a base and exponent pair which form one
/// factor of some product.
void BuildRankMap(Function &F);
unsigned getRank(Value *V);
Value *ReassociateExpression(BinaryOperator *I);
- void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops,
- unsigned Idx = 0);
+ void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
Value *OptimizeExpression(BinaryOperator *I,
SmallVectorImpl<ValueEntry> &Ops);
Value *OptimizeAdd(Instruction *I, SmallVectorImpl<ValueEntry> &Ops);
SmallVectorImpl<Factor> &Factors);
Value *OptimizeMul(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
void LinearizeExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops);
- void LinearizeExpr(BinaryOperator *I);
Value *RemoveFactorFromExpression(Value *V, Value *Factor);
void ReassociateInst(BasicBlock::iterator &BBI);
-
+
void RemoveDeadBinaryOp(Value *V);
};
}
// Public interface to the Reassociate pass
FunctionPass *llvm::createReassociatePass() { return new Reassociate(); }
+/// 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;
+}
+
void Reassociate::RemoveDeadBinaryOp(Value *V) {
- Instruction *Op = dyn_cast<Instruction>(V);
- if (!Op || !isa<BinaryOperator>(Op))
+ BinaryOperator *Op = dyn_cast<BinaryOperator>(V);
+ if (!Op)
return;
-
- Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
-
+
ValueRankMap.erase(Op);
DeadInsts.push_back(Op);
- RemoveDeadBinaryOp(LHS);
- RemoveDeadBinaryOp(RHS);
-}
+ BinaryOperator *LHS = isReassociableOp(Op->getOperand(0), Op->getOpcode());
+ BinaryOperator *RHS = isReassociableOp(Op->getOperand(1), Op->getOpcode());
+ Op->setOperand(0, UndefValue::get(Op->getType()));
+ Op->setOperand(1, UndefValue::get(Op->getType()));
+
+ if (LHS)
+ RemoveDeadBinaryOp(LHS);
+ if (RHS)
+ RemoveDeadBinaryOp(RHS);
+}
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::UDiv ||
I->getOpcode() == Instruction::SDiv ||
I->getOpcode() == Instruction::FDiv ||
I->getOpcode() == Instruction::URem ||
return ValueRankMap[I] = 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;
-}
-
/// LowerNegateToMultiply - Replace 0-X with X*-1.
///
-static Instruction *LowerNegateToMultiply(Instruction *Neg,
+static BinaryOperator *LowerNegateToMultiply(Instruction *Neg,
DenseMap<AssertingVH<Value>, unsigned> &ValueRankMap) {
Constant *Cst = Constant::getAllOnesValue(Neg->getType());
- Instruction *Res = BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
+ BinaryOperator *Res =
+ BinaryOperator::CreateMul(Neg->getOperand(1), Cst, "",Neg);
ValueRankMap.erase(Neg);
Res->takeName(Neg);
Neg->replaceAllUsesWith(Res);
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(dbgs() << "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);
-
- // Conservatively clear all the optional flags, which may not hold
- // after the reassociation.
- I->clearSubclassOptionalData();
- LHS->clearSubclassOptionalData();
- RHS->clearSubclassOptionalData();
-
- ++NumLinear;
- MadeChange = true;
- DEBUG(dbgs() << "Linearized: " << *I << '\n');
-
- // If D is part of this expression tree, tail recurse.
- if (isReassociableOp(I->getOperand(1), I->getOpcode()))
- LinearizeExpr(I);
-}
-
-
-/// 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 expression (((a+b)+c)+d), and collects information about the
-/// rank of the non-tree operands.
+/// 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.
+///
+/// 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, E, F, F, G, G.
+///
+/// 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.
///
-/// 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.
+/// In the above example either the right operand of A or the left operand of B
+/// will be replaced by undef. If it is B's operand then this gives:
///
+/// + | I
+/// / \ |
+/// + + | A, B - operand of B replaced with undef
+/// / \ \ |
+/// * + * | C, D, E
+/// / \ / \ / \ |
+/// + * | F, G
+///
+/// Note that such undef operands can only be reached by passing through 'I'.
+/// For example, if you visit operands recursively starting from a leaf node
+/// then you will never see such an undef operand unless you get back to 'I',
+/// which requires passing through a phi node.
+///
+/// Note that this routine may also mutate binary operators of the wrong type
+/// that have all uses inside the expression (i.e. only used by non-leaf nodes
+/// of the expression) if it can turn them into binary operators of the right
+/// type and thus make the expression bigger.
+
void Reassociate::LinearizeExprTree(BinaryOperator *I,
SmallVectorImpl<ValueEntry> &Ops) {
- Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
+ DEBUG(dbgs() << "LINEARIZE: " << *I << '\n');
+
+ // 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*, unsigned>, 8> Worklist; // (Op, Weight)
+ Worklist.push_back(std::make_pair(I, 1));
unsigned Opcode = I->getOpcode();
- // First step, linearize the expression if it is in ((A+B)+(C+D)) form.
- BinaryOperator *LHSBO = isReassociableOp(LHS, Opcode);
- BinaryOperator *RHSBO = isReassociableOp(RHS, Opcode);
+ // 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 SmallMap<Value*, unsigned, 8> LeafMap;
+ LeafMap Leaves; // Leaf -> Total weight so far.
+ SmallVector<Value*, 8> LeafOrder; // Ensure deterministic leaf output order.
- // 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);
- LHSBO = isReassociableOp(LHS, Opcode);
- }
- if (!RHSBO && RHS->hasOneUse() && BinaryOperator::isNeg(RHS)) {
- RHS = LowerNegateToMultiply(cast<Instruction>(RHS), ValueRankMap);
- RHSBO = isReassociableOp(RHS, Opcode);
- }
- }
+#ifndef NDEBUG
+ SmallPtrSet<Value*, 8> Visited; // For sanity checking the iteration scheme.
+#endif
+ while (!Worklist.empty()) {
+ std::pair<BinaryOperator*, unsigned> 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.
+ 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;
+ }
- 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;
- }
-
- // Turn X+(Y+Z) -> (Y+Z)+X
- std::swap(LHSBO, RHSBO);
- std::swap(LHS, RHS);
- bool Success = !I->swapOperands();
- assert(Success && "swapOperands failed");
- (void)Success;
- MadeChange = true;
- } else if (RHSBO) {
- // Turn (A+B)+(C+D) -> (((A+B)+C)+D). This guarantees the RHS is not
- // part of the expression tree.
- LinearizeExpr(I);
- LHS = LHSBO = cast<BinaryOperator>(I->getOperand(0));
- RHS = I->getOperand(1);
- RHSBO = 0;
- }
+ // 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.
+ It->second += Weight;
+
+ // 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;
- // 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!");
+ // 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;
+ }
- // Move LHS right before I to make sure that the tree expression dominates all
- // values.
- LHSBO->moveBefore(I);
+ // 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, ValueRankMap);
+ DEBUG(dbgs() << *BO << 'n');
+ Worklist.push_back(std::make_pair(BO, Weight));
+ MadeChange = true;
+ continue;
+ }
- // Linearize the expression tree on the LHS.
- LinearizeExprTree(LHSBO, Ops);
+ // 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;
+ }
+ }
- // 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()));
+ // 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())
+ // Leaf already output, or 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));
+ // Ensure the leaf is only output once.
+ Leaves.erase(It);
+ }
}
// 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,
- SmallVectorImpl<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(dbgs() << "RA: " << *I << '\n');
- I->setOperand(0, Ops[i].Op);
- I->setOperand(1, Ops[i+1].Op);
-
- // Clear all the optional flags, which may not hold after the
- // reassociation if the expression involved more than just this operation.
- if (Ops.size() != 2)
- I->clearSubclassOptionalData();
-
- DEBUG(dbgs() << "TO: " << *I << '\n');
+ 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
+ // 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();
+ NodesToRewrite.push_back(I);
+
+ // 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);
+
+ // 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) {
+ if (BinaryOperator *BO = isReassociableOp(OldLHS, Opcode))
+ NodesToRewrite.push_back(BO);
+ Op->setOperand(0, NewLHS);
+ }
+ if (NewRHS != OldRHS) {
+ if (BinaryOperator *BO = isReassociableOp(OldRHS, Opcode))
+ 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(dbgs() << "RA: " << *I << '\n');
- I->setOperand(1, Ops[i].Op);
+ // 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.
+ if (BinaryOperator *BO = isReassociableOp(Op->getOperand(1), Opcode))
+ NodesToRewrite.push_back(BO);
+ Op->setOperand(1, NewRHS);
+ ExpressionChanged = Op;
+ }
+ DEBUG(dbgs() << "TO: " << *Op << '\n');
+ MadeChange = true;
+ ++NumChanged;
+ }
- // Conservatively clear all the optional flags, which may not hold
- // after the reassociation.
- I->clearSubclassOptionalData();
+ // 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);
+ continue;
+ }
- DEBUG(dbgs() << "TO: " << *I << '\n');
+ // 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!");
+ DEBUG(dbgs() << "RA: " << *Op << '\n');
+ Op->setOperand(0, NodesToRewrite.back());
+ DEBUG(dbgs() << "TO: " << *Op << '\n');
+ ExpressionChanged = Op;
MadeChange = true;
++NumChanged;
}
-
- 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.
+ if (ExpressionChanged) {
+ do {
+ ExpressionChanged->clearSubclassOptionalData();
+ if (ExpressionChanged == I)
+ break;
+ 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)
+ RemoveDeadBinaryOp(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.
-//
+/// 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);
-
+
// 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,
// the constants. We assume that instcombine will clean up the mess later if
// 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(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;
- }
-
+ 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){
// 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)) {
// 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;
}
// 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() &&
+ (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);
return 0;
}
-// Scan backwards and forwards among values with the same rank as element i to
-// see if X exists. If X does not exist, return i. This is useful when
-// scanning for 'x' when we see '-x' because they both get the same rank.
+/// 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;
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;
-
+
SmallVector<ValueEntry, 8> Factors;
LinearizeExprTree(BO, Factors);
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))
break;
}
}
-
+
if (!FoundFactor) {
// Make sure to restore the operands to the expression tree.
RewriteExprTree(BO, Factors);
return 0;
}
-
+
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) {
- ValueRankMap.erase(BO);
- DeadInsts.push_back(BO);
+ RemoveDeadBinaryOp(BO);
V = Factors[0].Op;
} else {
RewriteExprTree(BO, Factors);
V = BO;
}
-
+
if (NeedsNegate)
V = BinaryOperator::CreateNeg(V, "neg", InsertPt);
-
+
return V;
}
/// Ops is the top-level list of add operands we're trying to factor.
static void FindSingleUseMultiplyFactors(Value *V,
SmallVectorImpl<Value*> &Factors,
- const SmallVectorImpl<ValueEntry> &Ops,
- bool IsRoot) {
- BinaryOperator *BO;
- if (!(V->hasOneUse() || V->use_empty()) || // More than one use.
- !(BO = dyn_cast<BinaryOperator>(V)) ||
- BO->getOpcode() != Instruction::Mul) {
+ const SmallVectorImpl<ValueEntry> &Ops) {
+ BinaryOperator *BO = isReassociableOp(V, Instruction::Mul);
+ if (!BO) {
Factors.push_back(V);
return;
}
-
- // If this value has a single use because it is another input to the add
- // tree we're reassociating and we dropped its use, it actually has two
- // uses and we can't factor it.
- if (!IsRoot) {
- for (unsigned i = 0, e = Ops.size(); i != e; ++i)
- if (Ops[i].Op == V) {
- Factors.push_back(V);
- return;
- }
- }
-
-
+
// Otherwise, add the LHS and RHS to the list of factors.
- FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops, false);
- FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops, false);
+ FindSingleUseMultiplyFactors(BO->getOperand(1), Factors, Ops);
+ FindSingleUseMultiplyFactors(BO->getOperand(0), Factors, Ops);
}
/// OptimizeAndOrXor - Optimize a series of operands to an 'and', 'or', or 'xor'
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());
++NumAnnihil;
continue;
}
-
+
// Drop pairs of values for Xor.
assert(Opcode == Instruction::Xor);
if (e == 2)
return Constant::getNullValue(Ops[0].Op->getType());
-
+
// Y ^ X^X -> Y
Ops.erase(Ops.begin()+i, Ops.begin()+i+2);
i -= 1; e -= 2;
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.push_back(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;
--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 = dyn_cast<BinaryOperator>(Ops[i].Op);
- if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
+ 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, true);
+ 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.
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');
// 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
+ // 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 = dyn_cast<BinaryOperator>(Ops[i].Op);
- if (BOp == 0 || BOp->getOpcode() != Instruction::Mul || !BOp->use_empty())
+ 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.
--i;
}
}
-
+
// No need for extra uses anymore.
delete DummyInst;
// 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;
- V = ReassociateExpression(cast<BinaryOperator>(V));
+ RedoInsts.push_back(V);
// Create the multiply.
Value *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.
- V2 = ReassociateExpression(cast<BinaryOperator>(V2));
-
+ RedoInsts.push_back(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;
}
/// \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;
- DenseMap<Value *, unsigned> FactorCounts;
- for (unsigned LastIdx = 0, Idx = 0, Size = Ops.size(); Idx < Size; ++Idx) {
- // Note that 'use_empty' uses means the only use is in the linearized tree
- // represented by Ops -- we remove the values from the actual operations to
- // reduce their use count.
- if (!Ops[Idx].Op->use_empty()) {
- if (LastIdx == Idx)
- ++LastIdx;
- continue;
- }
- if (LastIdx == Idx || Ops[LastIdx].Op != Ops[Idx].Op) {
- LastIdx = Idx;
- continue;
- }
+ 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.
- DenseMap<Value *, unsigned>::iterator CountIt;
- bool Inserted;
- llvm::tie(CountIt, Inserted)
- = FactorCounts.insert(std::make_pair(Ops[Idx].Op, 2));
- if (Inserted) {
- FactorPowerSum += 2;
- Factors.push_back(Factor(Ops[Idx].Op, 2));
- } else {
- ++CountIt->second;
- ++FactorPowerSum;
- }
+ 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
if (FactorPowerSum < 4)
return false;
- // Remove all the operands which are in the map.
- Ops.erase(std::remove_if(Ops.begin(), Ops.end(), IsValueInMap(FactorCounts)),
- Ops.end());
+ // 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;
- // Record the adjusted power for the simplification factors. We add back into
- // the Ops list any values with an odd power, and make the power even. This
- // allows the outer-most multiplication tree to remain in tact during
- // simplification.
- unsigned OldOpsSize = Ops.size();
- for (unsigned Idx = 0, Size = Factors.size(); Idx != Size; ++Idx) {
- Factors[Idx].Power = FactorCounts[Factors[Idx].Base];
- if (Factors[Idx].Power & 1) {
- Ops.push_back(ValueEntry(getRank(Factors[Idx].Base), Factors[Idx].Base));
- --Factors[Idx].Power;
- --FactorPowerSum;
- }
+ // 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);
- // Patch up the sort of the ops vector by sorting the factors we added back
- // onto the back, and merging the two sequences.
- if (OldOpsSize != Ops.size()) {
- SmallVectorImpl<ValueEntry>::iterator MiddleIt = Ops.begin() + OldOpsSize;
- std::sort(MiddleIt, Ops.end());
- std::inplace_merge(Ops.begin(), MiddleIt, Ops.end());
- }
-
std::sort(Factors.begin(), Factors.end(), Factor::PowerDescendingSorter());
return true;
}
// 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.
- Factors[LastIdx].Base
- = ReassociateExpression(
- cast<BinaryOperator>(buildMultiplyTree(Builder, InnerProduct)));
+ Factors[LastIdx].Base = buildMultiplyTree(Builder, InnerProduct);
+ RedoInsts.push_back(Factors[LastIdx].Base);
LastIdx = Idx;
}
if (OuterProduct.size() == 1)
return OuterProduct.front();
- return ReassociateExpression(
- cast<BinaryOperator>(buildMultiplyTree(Builder, OuterProduct)));
+ Value *V = buildMultiplyTree(Builder, OuterProduct);
+ return V;
}
Value *Reassociate::OptimizeMul(BinaryOperator *I,
if (Ops.size() == 1) return Ops[0].Op;
unsigned Opcode = I->getOpcode();
-
+
if (Constant *V1 = dyn_cast<Constant>(Ops[Ops.size()-2].Op))
if (Constant *V2 = dyn_cast<Constant>(Ops.back().Op)) {
Ops.pop_back();
++NumAnnihil;
return CstVal;
}
-
+
if (cast<ConstantInt>(CstVal)->isOne())
Ops.pop_back(); // X * 1 -> X
break;
return 0;
}
-
/// ReassociateInst - Inspect and reassociate the instruction at the
/// given position, post-incrementing the position.
void Reassociate::ReassociateInst(BasicBlock::iterator &BBI) {
BI = NI;
}
- // Reject cases where it is pointless to do this.
- if (!isa<BinaryOperator>(BI) || BI->getType()->isFloatingPointTy() ||
- BI->getType()->isVectorTy())
- return; // Floating point ops are not associative.
+ // 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 (isa<BinaryOperator>(BI) &&
+ (BI->getType()->isFloatingPointTy() || BI->getType()->isVectorTy())) {
+ // FAdd and FMul can be commuted.
+ if (BI->getOpcode() != Instruction::FMul &&
+ BI->getOpcode() != Instruction::FAdd)
+ return;
+
+ Value *LHS = BI->getOperand(0);
+ Value *RHS = BI->getOperand(1);
+ unsigned LHSRank = getRank(LHS);
+ unsigned RHSRank = getRank(RHS);
+
+ // Sort the operands by rank.
+ if (RHSRank < LHSRank) {
+ BI->setOperand(0, RHS);
+ BI->setOperand(1, LHS);
+ }
+
+ return;
+ }
+
+ // Do not reassociate operations that we do not understand.
+ if (!isa<BinaryOperator>(BI))
+ return;
// Do not reassociate boolean (i1) expressions. We want to preserve the
// original order of evaluation for short-circuited comparisons that
if (I->hasOneUse() && isReassociableOp(I->use_back(), I->getOpcode()))
return;
- // If this is an add tree that is used by a sub instruction, ignore it
+ // 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)
}
Value *Reassociate::ReassociateExpression(BinaryOperator *I) {
-
+
// First, walk the expression tree, linearizing the tree, collecting the
// operand information.
SmallVector<ValueEntry, 8> Ops;
LinearizeExprTree(I, Ops);
-
+
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)) {
++NumAnnihil;
return V;
}
-
+
// 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
ValueEntry Tmp = Ops.pop_back_val();
Ops.insert(Ops.begin(), Tmp);
}
-
+
DEBUG(dbgs() << "RAOut:\t"; PrintOps(I, Ops); dbgs() << '\n');
-
+
if (Ops.size() == 1) {
// This expression tree simplified to something that isn't a tree,
// eliminate it.
RemoveDeadBinaryOp(I);
return Ops[0].Op;
}
-
+
// 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) {
// Recalculate the rank map for F
BuildRankMap(F);
ReassociateInst(BBI);
}
+ // We are done with the rank map.
+ RankMap.clear();
+ ValueRankMap.clear();
+
// Now that we're done, delete any instructions which are no longer used.
while (!DeadInsts.empty())
if (Value *V = DeadInsts.pop_back_val())
RecursivelyDeleteTriviallyDeadInstructions(V);
- // We are done with the rank map.
- RankMap.clear();
- ValueRankMap.clear();
return MadeChange;
}
-
projects / oota-llvm.git / blobdiff