Don't create ISD::FNEG nodes after legalize if they aren't legal.
Simplify x+0 to x in unsafe-fp-math mode. This avoids a bunch of
redundant work in many cases, because in unsafe-fp-math mode,
ISD::FADD with a constant is considered free to negate, so the
DAGCombiner often negates x+0 to -0-x thinking it's free, when
in reality the end result is -x, which is more expensive than x.
Also, combine x*0 to 0.
This fixes PR3374.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62789 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index f7c1d06..e494da3 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3814,6 +3814,9 @@
// canonicalize constant to RHS
if (N0CFP && !N1CFP)
return DAG.getNode(ISD::FADD, VT, N1, N0);
+ // fold (A + 0) -> A
+ if (UnsafeFPMath && N1CFP && N1CFP->getValueAPF().isZero())
+ return N0;
// fold (A + (-B)) -> A-B
if (isNegatibleForFree(N1, LegalOperations) == 2)
return DAG.getNode(ISD::FSUB, VT, N0,
@@ -3852,7 +3855,8 @@
if (UnsafeFPMath && N0CFP && N0CFP->getValueAPF().isZero()) {
if (isNegatibleForFree(N1, LegalOperations))
return GetNegatedExpression(N1, DAG, LegalOperations);
- return DAG.getNode(ISD::FNEG, VT, N1);
+ if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
+ return DAG.getNode(ISD::FNEG, VT, N1);
}
// fold (A-(-B)) -> A+B
if (isNegatibleForFree(N1, LegalOperations))
@@ -3881,12 +3885,16 @@
// canonicalize constant to RHS
if (N0CFP && !N1CFP)
return DAG.getNode(ISD::FMUL, VT, N1, N0);
+ // fold (A * 0) -> 0
+ if (UnsafeFPMath && N1CFP && N1CFP->getValueAPF().isZero())
+ return N1;
// fold (fmul X, 2.0) -> (fadd X, X)
if (N1CFP && N1CFP->isExactlyValue(+2.0))
return DAG.getNode(ISD::FADD, VT, N0, N0);
// fold (fmul X, -1.0) -> (fneg X)
if (N1CFP && N1CFP->isExactlyValue(-1.0))
- return DAG.getNode(ISD::FNEG, VT, N0);
+ if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
+ return DAG.getNode(ISD::FNEG, VT, N0);
// -X * -Y -> X*Y
if (char LHSNeg = isNegatibleForFree(N0, LegalOperations)) {
@@ -3970,10 +3978,13 @@
const APFloat& V = N1CFP->getValueAPF();
// copysign(x, c1) -> fabs(x) iff ispos(c1)
// copysign(x, c1) -> fneg(fabs(x)) iff isneg(c1)
- if (!V.isNegative())
- return DAG.getNode(ISD::FABS, VT, N0);
- else
- return DAG.getNode(ISD::FNEG, VT, DAG.getNode(ISD::FABS, VT, N0));
+ if (!V.isNegative()) {
+ if (!LegalOperations || TLI.isOperationLegal(ISD::FABS, VT))
+ return DAG.getNode(ISD::FABS, VT, N0);
+ } else {
+ if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
+ return DAG.getNode(ISD::FNEG, VT, DAG.getNode(ISD::FABS, VT, N0));
+ }
}
// copysign(fabs(x), y) -> copysign(x, y)