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-rw-r--r--llvm/lib/Transforms/Scalar/Reassociate.cpp91
1 files changed, 65 insertions, 26 deletions
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index dc44ad593f2..e495ffafbb9 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -79,8 +79,8 @@ namespace {
void BuildRankMap(Function &F);
unsigned getRank(Value *V);
void ReassociateExpression(BinaryOperator *I);
- void RewriteExprTree(BinaryOperator *I, unsigned Idx,
- std::vector<ValueEntry> &Ops);
+ 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);
@@ -174,7 +174,7 @@ unsigned Reassociate::getRank(Value *V) {
/// 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) &&
+ if ((V->hasOneUse() || V->use_empty()) && isa<Instruction>(V) &&
cast<Instruction>(V)->getOpcode() == Opcode)
return cast<BinaryOperator>(V);
return 0;
@@ -234,6 +234,10 @@ void Reassociate::LinearizeExpr(BinaryOperator *I) {
/// form of the the expression (((a+b)+c)+d), and collects information about the
/// rank of the non-tree operands.
///
+/// 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.
+///
void Reassociate::LinearizeExprTree(BinaryOperator *I,
std::vector<ValueEntry> &Ops) {
Value *LHS = I->getOperand(0), *RHS = I->getOperand(1);
@@ -262,6 +266,10 @@ void Reassociate::LinearizeExprTree(BinaryOperator *I,
// 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
@@ -293,13 +301,17 @@ void Reassociate::LinearizeExprTree(BinaryOperator *I,
// 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()));
}
// 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.
-void Reassociate::RewriteExprTree(BinaryOperator *I, unsigned i,
- std::vector<ValueEntry> &Ops) {
+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) {
@@ -334,7 +346,7 @@ void Reassociate::RewriteExprTree(BinaryOperator *I, unsigned i,
// 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, i+1, Ops);
+ RewriteExprTree(LHS, Ops, i+1);
}
@@ -474,14 +486,36 @@ Value *Reassociate::RemoveFactorFromExpression(Value *V, Value *Factor) {
Factors.erase(Factors.begin()+i);
break;
}
- if (!FoundFactor) return 0;
+ 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, 0, Factors);
+ RewriteExprTree(BO, Factors);
return BO;
}
+/// FindSingleUseMultiplyFactors - If V is a single-use multiply, recursively
+/// add its operands as factors, otherwise add V to the list of factors.
+static void FindSingleUseMultiplyFactors(Value *V,
+ std::vector<Value*> &Factors) {
+ BinaryOperator *BO;
+ if ((!V->hasOneUse() && !V->use_empty()) ||
+ !(BO = dyn_cast<BinaryOperator>(V)) ||
+ BO->getOpcode() != Instruction::Mul) {
+ Factors.push_back(V);
+ return;
+ }
+
+ // Otherwise, add the LHS and RHS to the list of factors.
+ FindSingleUseMultiplyFactors(BO->getOperand(1), Factors);
+ FindSingleUseMultiplyFactors(BO->getOperand(0), Factors);
+}
+
+
Value *Reassociate::OptimizeExpression(BinaryOperator *I,
std::vector<ValueEntry> &Ops) {
@@ -627,26 +661,26 @@ Value *Reassociate::OptimizeExpression(BinaryOperator *I,
if (!I->getType()->isFloatingPoint()) {
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->hasOneUse()) {
+ if (BOp->getOpcode() == Instruction::Mul && BOp->use_empty()) {
// Compute all of the factors of this added value.
- std::vector<ValueEntry> Factors;
- LinearizeExprTree(BOp, Factors);
+ 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].Op];
- if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[0].Op; }
- if (Factors[0].Op != Factors[1].Op) { // Don't double count A*A.
- Occ = ++FactorOccurrences[Factors[1].Op];
- if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[1].Op; }
+ 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].Op).second) {
- unsigned Occ = ++FactorOccurrences[Factors[i].Op];
- if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[i].Op; }
+ if (Duplicates.insert(Factors[i]).second) {
+ unsigned Occ = ++FactorOccurrences[Factors[i]];
+ if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[i]; }
}
}
}
@@ -675,21 +709,26 @@ Value *Reassociate::OptimizeExpression(BinaryOperator *I,
// No need for extra uses anymore.
delete DummyInst;
+ unsigned NumAddedValues = NewMulOps.size();
Value *V = EmitAddTreeOfValues(I, NewMulOps);
- // FIXME: Must optimize V now, to handle this case:
- // A*A*B + A*A*C -> A*(A*B+A*C) -> A*(A*(B+C))
- V = BinaryOperator::createMul(V, MaxOccVal, "tmp", I);
+ 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.size() == 0)
- return V;
+ return V2;
// Add the new value to the list of things being added.
- Ops.insert(Ops.begin(), ValueEntry(getRank(V), V));
+ Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
// Rewrite the tree so that there is now a use of V.
- RewriteExprTree(I, 0, Ops);
+ RewriteExprTree(I, Ops);
return OptimizeExpression(I, Ops);
}
break;
@@ -808,7 +847,7 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) {
} else {
// Now that we ordered and optimized the expressions, splat them back into
// the expression tree, removing any unneeded nodes.
- RewriteExprTree(I, 0, Ops);
+ RewriteExprTree(I, Ops);
}
}
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