Teach GetNegatedExpression to negate 0-B to B in UnsafeFPMath mode, and
visitFSUB to fold 0-B to -B in UnsafeFPMath mode. Also change visitFNEG
to use isNegatibleForFree/GetNegatedExpression instead of doing a subset
of the same thing manually.
This fixes test/CodeGen/X86/negative-sin.ll.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37842 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index cb7276e..d69aede 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -429,6 +429,11 @@
case ISD::FSUB:
// We can't turn -(A-B) into B-A when we honor signed zeros.
assert(UnsafeFPMath);
+
+ // -(0-B) -> B
+ if (ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(Op.getOperand(0)))
+ if (N0CFP->getValue() == 0.0)
+ return Op.getOperand(1);
// -(A-B) -> B-A
return DAG.getNode(ISD::FSUB, Op.getValueType(), Op.getOperand(1),
@@ -3025,6 +3030,12 @@
// fold (fsub c1, c2) -> c1-c2
if (N0CFP && N1CFP)
return DAG.getNode(ISD::FSUB, VT, N0, N1);
+ // fold (0-B) -> -B
+ if (UnsafeFPMath && N0CFP && N0CFP->getValue() == 0.0) {
+ if (isNegatibleForFree(N1))
+ return GetNegatedExpression(N1, DAG);
+ return DAG.getNode(ISD::FNEG, VT, N1);
+ }
// fold (A-(-B)) -> A+B
if (isNegatibleForFree(N1))
return DAG.getNode(ISD::FADD, VT, N0, GetNegatedExpression(N1, DAG));
@@ -3297,18 +3308,10 @@
SDOperand DAGCombiner::visitFNEG(SDNode *N) {
SDOperand N0 = N->getOperand(0);
- ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(N0);
- MVT::ValueType VT = N->getValueType(0);
- // fold (fneg c1) -> -c1
- if (N0CFP)
- return DAG.getNode(ISD::FNEG, VT, N0);
- // fold (fneg (sub x, y)) -> (sub y, x)
- if (N0.getOpcode() == ISD::SUB)
- return DAG.getNode(ISD::SUB, VT, N0.getOperand(1), N0.getOperand(0));
- // fold (fneg (fneg x)) -> x
- if (N0.getOpcode() == ISD::FNEG)
- return N0.getOperand(0);
+ if (isNegatibleForFree(N0))
+ return GetNegatedExpression(N0, DAG);
+
return SDOperand();
}