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Teach GetNegatedExpression to negate 0-B to B in UnsafeFPMath mode, and

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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
This commit is contained in:
Dan Gohman 2007-07-02 15:48:56 +00:00
parent 03de31acae
commit 23ff1826b9
1 changed files with 14 additions and 11 deletions
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25
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -429,6 +429,11 @@ static SDOperand GetNegatedExpression(SDOperand Op, SelectionDAG &DAG,
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 @@ SDOperand DAGCombiner::visitFSUB(SDNode *N) {
// 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::visitFP_EXTEND(SDNode *N) {
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();
}