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move the rest of the add optimization code out to OptimizeAdd,

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improve some comments, simplify a bit of code.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92363 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-12-31 18:17:13 +00:00
parent 9fdaefad58
commit 94285e620b
1 changed files with 94 additions and 93 deletions
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187
lib/Transforms/Scalar/Reassociate.cpp
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@ -92,7 +92,7 @@ namespace {
void RewriteExprTree(BinaryOperator *I, std::vector<ValueEntry> &Ops,
unsigned Idx = 0);
Value *OptimizeExpression(BinaryOperator *I, std::vector<ValueEntry> &Ops);
Value *OptimizeAdd(std::vector<ValueEntry> &Ops);
Value *OptimizeAdd(Instruction *I, std::vector<ValueEntry> &Ops);
void LinearizeExprTree(BinaryOperator *I, std::vector<ValueEntry> &Ops);
void LinearizeExpr(BinaryOperator *I);
Value *RemoveFactorFromExpression(Value *V, Value *Factor);
@ -598,7 +598,7 @@ static Value *OptimizeAndOrXor(unsigned Opcode, std::vector<ValueEntry> &Ops) {
/// OptimizeAdd - Optimize a series of operands to an 'add' instruction. This
/// optimizes based on identities. If it can be reduced to a single Value, it
/// is returned, otherwise the Ops list is mutated as necessary.
Value *Reassociate::OptimizeAdd(std::vector<ValueEntry> &Ops) {
Value *Reassociate::OptimizeAdd(Instruction *I, std::vector<ValueEntry> &Ops) {
// Scan the operand lists looking for X and -X pairs. If we find any, we
// can simplify the expression. X+-X == 0.
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
@ -626,6 +626,94 @@ Value *Reassociate::OptimizeAdd(std::vector<ValueEntry> &Ops) {
--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.
SmallPtrSet<BinaryOperator*, 4> Multiplies;
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())
continue;
// If we've already seen this multiply, don't revisit it.
if (!Multiplies.insert(BOp)) continue;
// Compute all of the factors of this added value.
SmallVector<Value*, 8> Factors;
FindSingleUseMultiplyFactors(BOp, Factors);
assert(Factors.size() > 1 && "Bad linearize!");
// Add one to FactorOccurrences for each unique factor in this op.
if (Factors.size() == 2) {
unsigned Occ = ++FactorOccurrences[Factors[0]];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[0]; }
if (Factors[0] != Factors[1]) { // Don't double count A*A.
Occ = ++FactorOccurrences[Factors[1]];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[1]; }
}
} else {
SmallPtrSet<Value*, 4> Duplicates;
for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
if (!Duplicates.insert(Factors[i])) continue;
unsigned Occ = ++FactorOccurrences[Factors[i]];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[i]; }
}
}
}
// If any factor occurred more than one time, we can pull it out.
if (MaxOcc > 1) {
DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << "\n");
++NumFactor;
// Create a new instruction that uses the MaxOccVal twice. If we don't do
// this, we could otherwise run into situations where removing a factor
// from an expression will drop a use of maxocc, and this can cause
// RemoveFactorFromExpression on successive values to behave differently.
Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
SmallVector<Value*, 4> NewMulOps;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
NewMulOps.push_back(V);
Ops.erase(Ops.begin()+i);
--i; --e;
}
}
// No need for extra uses anymore.
delete DummyInst;
unsigned NumAddedValues = NewMulOps.size();
Value *V = EmitAddTreeOfValues(I, NewMulOps);
Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
// Now that we have inserted V and its sole use, optimize it. This allows
// us to handle cases that require multiple factoring steps, such as this:
// A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
if (NumAddedValues > 1)
ReassociateExpression(cast<BinaryOperator>(V));
// 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 fact, such as
// "A*B + A*C + D" -> "A*(B+C) + D". Add the new multiply to the list of
// things being added.
Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
}
return 0;
}
@ -692,98 +780,11 @@ Value *Reassociate::OptimizeExpression(BinaryOperator *I,
case Instruction::Add: {
unsigned NumOps = Ops.size();
if (Value *Result = OptimizeAdd(Ops))
if (Value *Result = OptimizeAdd(I, Ops))
return Result;
IterateOptimization |= Ops.size() != NumOps;
}
// 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.
SmallPtrSet<BinaryOperator*, 4> Multiplies;
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())
continue;
// If we've already seen this multiply, don't revisit it.
if (!Multiplies.insert(BOp)) continue;
// Compute all of the factors of this added value.
SmallVector<Value*, 8> Factors;
FindSingleUseMultiplyFactors(BOp, Factors);
assert(Factors.size() > 1 && "Bad linearize!");
// Add one to FactorOccurrences for each unique factor in this op.
if (Factors.size() == 2) {
unsigned Occ = ++FactorOccurrences[Factors[0]];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[0]; }
if (Factors[0] != Factors[1]) { // Don't double count A*A.
Occ = ++FactorOccurrences[Factors[1]];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[1]; }
}
} else {
SmallPtrSet<Value*, 4> Duplicates;
for (unsigned i = 0, e = Factors.size(); i != e; ++i) {
if (!Duplicates.insert(Factors[i])) continue;
unsigned Occ = ++FactorOccurrences[Factors[i]];
if (Occ > MaxOcc) { MaxOcc = Occ; MaxOccVal = Factors[i]; }
}
}
}
// If any factor occurred more than one time, we can pull it out.
if (MaxOcc > 1) {
DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << "\n");
// Create a new instruction that uses the MaxOccVal twice. If we don't do
// this, we could otherwise run into situations where removing a factor
// from an expression will drop a use of maxocc, and this can cause
// RemoveFactorFromExpression on successive values to behave differently.
Instruction *DummyInst = BinaryOperator::CreateAdd(MaxOccVal, MaxOccVal);
SmallVector<Value*, 4> NewMulOps;
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
if (Value *V = RemoveFactorFromExpression(Ops[i].Op, MaxOccVal)) {
NewMulOps.push_back(V);
Ops.erase(Ops.begin()+i);
--i; --e;
}
}
// No need for extra uses anymore.
delete DummyInst;
unsigned NumAddedValues = NewMulOps.size();
Value *V = EmitAddTreeOfValues(I, NewMulOps);
Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
// Now that we have inserted V and its sole use, optimize it. This allows
// us to handle cases that require multiple factoring steps, such as this:
// A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
if (NumAddedValues > 1)
ReassociateExpression(cast<BinaryOperator>(V));
++NumFactor;
if (Ops.empty())
return V2;
// Add the new value to the list of things being added.
Ops.insert(Ops.begin(), ValueEntry(getRank(V2), V2));
// Rewrite the tree so that there is now a use of V.
RewriteExprTree(I, Ops);
return OptimizeExpression(I, Ops);
}
break;
//case Instruction::Mul:
}
@ -854,7 +855,7 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) {
std::vector<ValueEntry> Ops;
LinearizeExprTree(I, Ops);
DEBUG(errs() << "RAIn:\t"; PrintOps(I, Ops); errs() << "\n");
DEBUG(errs() << "RAIn:\t"; PrintOps(I, Ops); errs() << '\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
@ -869,7 +870,7 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) {
if (Value *V = OptimizeExpression(I, Ops)) {
// This expression tree simplified to something that isn't a tree,
// eliminate it.
DEBUG(errs() << "Reassoc to scalar: " << *V << "\n");
DEBUG(errs() << "Reassoc to scalar: " << *V << '\n');
I->replaceAllUsesWith(V);
RemoveDeadBinaryOp(I);
++NumAnnihil;
@ -888,7 +889,7 @@ void Reassociate::ReassociateExpression(BinaryOperator *I) {
Ops.pop_back();
}
DEBUG(errs() << "RAOut:\t"; PrintOps(I, Ops); errs() << "\n");
DEBUG(errs() << "RAOut:\t"; PrintOps(I, Ops); errs() << '\n');
if (Ops.size() == 1) {
// This expression tree simplified to something that isn't a tree,