teach reassociate to factor x+x+x -> x*3. While I'm at it,
fix RemoveDeadBinaryOp to actually do something.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92368 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/Reassociate.cpp b/lib/Transforms/Scalar/Reassociate.cpp
index fe63381..e0528f7 100644
--- a/lib/Transforms/Scalar/Reassociate.cpp
+++ b/lib/Transforms/Scalar/Reassociate.cpp
@@ -88,7 +88,7 @@
private:
void BuildRankMap(Function &F);
unsigned getRank(Value *V);
- void ReassociateExpression(BinaryOperator *I);
+ Value *ReassociateExpression(BinaryOperator *I);
void RewriteExprTree(BinaryOperator *I, SmallVectorImpl<ValueEntry> &Ops,
unsigned Idx = 0);
Value *OptimizeExpression(BinaryOperator *I,
@@ -111,10 +111,13 @@
void Reassociate::RemoveDeadBinaryOp(Value *V) {
Instruction *Op = dyn_cast<Instruction>(V);
- if (!Op || !isa<BinaryOperator>(Op) || !isa<CmpInst>(Op) || !Op->use_empty())
+ if (!Op || !isa<BinaryOperator>(Op) || !Op->use_empty())
return;
Value *LHS = Op->getOperand(0), *RHS = Op->getOperand(1);
+
+ ValueRankMap.erase(Op);
+ Op->eraseFromParent();
RemoveDeadBinaryOp(LHS);
RemoveDeadBinaryOp(RHS);
}
@@ -602,15 +605,57 @@
/// is returned, otherwise the Ops list is mutated as necessary.
Value *Reassociate::OptimizeAdd(Instruction *I,
SmallVectorImpl<ValueEntry> &Ops) {
+ SmallPtrSet<Value*, 8> OperandsSeen;
+
+Restart:
+ OperandsSeen.clear();
+
// Scan the operand lists looking for X and -X pairs. If we find any, we
- // can simplify the expression. X+-X == 0.
+ // can simplify the expression. X+-X == 0. While we're at it, scan for any
+ // duplicates. We want to canonicalize Y+Y+Y+Z -> 3*Y+Z.
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
- assert(i < Ops.size());
+ Value *TheOp = Ops[i].Op;
+ // Check to see if we've seen this operand before. If so, we factor all
+ // instances of the operand together.
+ if (!OperandsSeen.insert(TheOp)) {
+ // Rescan the list, removing all instances of this operand from the expr.
+ unsigned NumFound = 0;
+ for (unsigned j = 0, je = Ops.size(); j != je; ++j) {
+ if (Ops[j].Op != TheOp) continue;
+ ++NumFound;
+ Ops.erase(Ops.begin()+j);
+ --j; --je;
+ }
+
+ /*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
+ Mul = ReassociateExpression(cast<BinaryOperator>(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));
+ goto Restart;
+ }
+
// Check for X and -X in the operand list.
- if (!BinaryOperator::isNeg(Ops[i].Op))
+ if (!BinaryOperator::isNeg(TheOp))
continue;
- Value *X = BinaryOperator::getNegArgument(Ops[i].Op);
+ Value *X = BinaryOperator::getNegArgument(TheOp);
unsigned FoundX = FindInOperandList(Ops, i, X);
if (FoundX == i)
continue;
@@ -639,7 +684,6 @@
// 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) {
@@ -647,9 +691,6 @@
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);
@@ -676,7 +717,7 @@
// If any factor occurred more than one time, we can pull it out.
if (MaxOcc > 1) {
- DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << "\n");
+ DEBUG(errs() << "\nFACTORING [" << MaxOcc << "]: " << *MaxOccVal << '\n');
++NumFactor;
// Create a new instruction that uses the MaxOccVal twice. If we don't do
@@ -698,13 +739,17 @@
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:
+ // Now that we have inserted the add tree, optimize it. This allows us to
+ // handle cases that require multiple factoring steps, such as this:
// A*A*B + A*A*C --> A*(A*B+A*C) --> A*(A*(B+C))
assert(NumAddedValues > 1 && "Each occurrence should contribute a value");
- ReassociateExpression(cast<BinaryOperator>(V));
+ V = ReassociateExpression(cast<BinaryOperator>(V));
+
+ // Create the multiply.
+ Value *V2 = BinaryOperator::CreateMul(V, MaxOccVal, "tmp", I);
+
+ // FIXME: Should rerun 'ReassociateExpression' on the mul too??
// 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)".
@@ -852,9 +897,10 @@
}
}
-void Reassociate::ReassociateExpression(BinaryOperator *I) {
+Value *Reassociate::ReassociateExpression(BinaryOperator *I) {
- // First, walk the expression tree, linearizing the tree, collecting
+ // First, walk the expression tree, linearizing the tree, collecting the
+ // operand information.
SmallVector<ValueEntry, 8> Ops;
LinearizeExprTree(I, Ops);
@@ -877,7 +923,7 @@
I->replaceAllUsesWith(V);
RemoveDeadBinaryOp(I);
++NumAnnihil;
- return;
+ return V;
}
// We want to sink immediates as deeply as possible except in the case where
@@ -899,11 +945,13 @@
// eliminate it.
I->replaceAllUsesWith(Ops[0].Op);
RemoveDeadBinaryOp(I);
- } else {
- // Now that we ordered and optimized the expressions, splat them back into
- // the expression tree, removing any unneeded nodes.
- RewriteExprTree(I, Ops);
+ 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;
}