[InstCombine] -X / C --> X / -C for FP
We already do this in DAGCombiner, but it should
also be good to eliminate the fsub use in IR.
llvm-svn: 325648
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index cb42d24..ec62beb 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1285,12 +1285,18 @@
return nullptr;
}
-/// Try to convert X/C into X * (1/C).
+/// Remove negation and try to convert division into multiplication.
static Instruction *foldFDivConstantDivisor(BinaryOperator &I) {
Constant *C;
if (!match(I.getOperand(1), m_Constant(C)))
return nullptr;
+ // -X / C --> X / -C
+ Value *X;
+ if (match(I.getOperand(0), m_FNeg(m_Value(X))))
+ return BinaryOperator::CreateWithCopiedFlags(Instruction::FDiv, X,
+ ConstantExpr::getFNeg(C), &I);
+
// If the constant divisor has an exact inverse, this is always safe. If not,
// then we can still create a reciprocal if fast-math-flags allow it and the
// constant is a regular number (not zero, infinite, or denormal).
@@ -1305,6 +1311,7 @@
if (!RecipC->isNormalFP())
return nullptr;
+ // X / C --> X * (1 / C)
return BinaryOperator::CreateWithCopiedFlags(
Instruction::FMul, I.getOperand(0), RecipC, &I);
}
@@ -1345,11 +1352,11 @@
SQ.getWithInstruction(&I)))
return replaceInstUsesWith(I, V);
- if (Instruction *FMul = foldFDivConstantDivisor(I))
- return FMul;
+ if (Instruction *R = foldFDivConstantDivisor(I))
+ return R;
- if (Instruction *NewFDiv = foldFDivConstantDividend(I))
- return NewFDiv;
+ if (Instruction *R = foldFDivConstantDividend(I))
+ return R;
if (isa<Constant>(Op0))
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))