return BinaryOperator::CreateFMul(FDiv.getOperand(0), RecipCFP);
}
+/// Try to strength-reduce C / X expressions where X includes another constant.
+static Instruction *foldFDivConstantDividend(BinaryOperator &I) {
+ Constant *C1;
+ if (!I.isFast() || !match(I.getOperand(0), m_Constant(C1)))
+ return nullptr;
+
+ Value *X;
+ Constant *C2, *NewC = nullptr;
+ if (match(I.getOperand(1), m_FMul(m_Value(X), m_Constant(C2)))) {
+ // C1 / (X * C2) --> (C1 / C2) / X
+ NewC = ConstantExpr::getFDiv(C1, C2);
+ } else if (match(I.getOperand(1), m_FDiv(m_Value(X), m_Constant(C2)))) {
+ // C1 / (X / C2) --> (C1 * C2) / X
+ NewC = ConstantExpr::getFMul(C1, C2);
+ }
+ // Disallow denormal constants because we don't know what would happen
+ // on all targets.
+ // TODO: Use Intrinsic::canonicalize or let function attributes tell us that
+ // denorms are flushed?
+ if (!NewC || !NewC->isNormalFP())
+ return nullptr;
+
+ return BinaryOperator::CreateWithCopiedFlags(Instruction::FDiv, NewC, X, &I);
+}
+
Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
return nullptr;
}
- if (AllowReassociate && isa<Constant>(Op0)) {
- Constant *C1 = cast<Constant>(Op0), *C2;
- Constant *Fold = nullptr;
- Value *X;
- bool CreateDiv = true;
-
- // C1 / (X*C2) => (C1/C2) / X
- if (match(Op1, m_FMul(m_Value(X), m_Constant(C2))))
- Fold = ConstantExpr::getFDiv(C1, C2);
- else if (match(Op1, m_FDiv(m_Value(X), m_Constant(C2)))) {
- // C1 / (X/C2) => (C1*C2) / X
- Fold = ConstantExpr::getFMul(C1, C2);
- } else if (match(Op1, m_FDiv(m_Constant(C2), m_Value(X)))) {
- // C1 / (C2/X) => (C1/C2) * X
- Fold = ConstantExpr::getFDiv(C1, C2);
- CreateDiv = false;
- }
-
- if (Fold && Fold->isNormalFP()) {
- Instruction *R = CreateDiv ? BinaryOperator::CreateFDiv(Fold, X)
- : BinaryOperator::CreateFMul(X, Fold);
- R->setFastMathFlags(I.getFastMathFlags());
- return R;
- }
- return nullptr;
- }
+ if (Instruction *NewFDiv = foldFDivConstantDividend(I))
+ return NewFDiv;
if (AllowReassociate) {
Value *X, *Y;