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Standardize comments about folding xforms.

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llvm-svn: 63443
This commit is contained in:
Bill Wendling 2009-01-30 23:10:18 +00:00
parent 67737da99b
commit cebc5ac36d
1 changed files with 10 additions and 10 deletions
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20
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -337,23 +337,23 @@ static char isNegatibleForFree(SDValue Op, bool LegalOperations,
// FIXME: determine better conditions for this xform.
if (!UnsafeFPMath) return 0;
// -(A+B) -> -A - B
// fold (fsub (fadd A, B)) -> (fsub (fneg A), B)
if (char V = isNegatibleForFree(Op.getOperand(0), LegalOperations, Depth+1))
return V;
// -(A+B) -> -B - A
// fold (fneg (fadd A, B)) -> (fsub (fneg B), A)
return isNegatibleForFree(Op.getOperand(1), LegalOperations, Depth+1);
case ISD::FSUB:
// We can't turn -(A-B) into B-A when we honor signed zeros.
if (!UnsafeFPMath) return 0;
// -(A-B) -> B-A
// fold (fneg (fsub A, B)) -> (fsub B, A)
return 1;
case ISD::FMUL:
case ISD::FDIV:
if (HonorSignDependentRoundingFPMath()) return 0;
// -(X*Y) -> (-X * Y) or (X*-Y)
// fold (fneg (fmul X, Y)) -> (fmul (fneg X), Y) or (fmul X, (fneg Y))
if (char V = isNegatibleForFree(Op.getOperand(0), LegalOperations, Depth+1))
return V;
@ -388,13 +388,13 @@ static SDValue GetNegatedExpression(SDValue Op, SelectionDAG &DAG,
// FIXME: determine better conditions for this xform.
assert(UnsafeFPMath);
// -(A+B) -> -A - B
// fold (fneg (fadd A, B)) -> (fsub (fneg A), B)
if (isNegatibleForFree(Op.getOperand(0), LegalOperations, Depth+1))
return DAG.getNode(ISD::FSUB, Op.getDebugLoc(), Op.getValueType(),
GetNegatedExpression(Op.getOperand(0), DAG,
LegalOperations, Depth+1),
Op.getOperand(1));
// -(A+B) -> -B - A
// fold (fneg (fadd A, B)) -> (fsub (fneg B), A)
return DAG.getNode(ISD::FSUB, Op.getDebugLoc(), Op.getValueType(),
GetNegatedExpression(Op.getOperand(1), DAG,
LegalOperations, Depth+1),
@ -403,12 +403,12 @@ static SDValue GetNegatedExpression(SDValue Op, SelectionDAG &DAG,
// We can't turn -(A-B) into B-A when we honor signed zeros.
assert(UnsafeFPMath);
// -(0-B) -> B
// fold (fneg (fsub 0, B)) -> B
if (ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(Op.getOperand(0)))
if (N0CFP->getValueAPF().isZero())
return Op.getOperand(1);
// -(A-B) -> B-A
// fold (fneg (fsub A, B)) -> (fsub B, A)
return DAG.getNode(ISD::FSUB, Op.getDebugLoc(), Op.getValueType(),
Op.getOperand(1), Op.getOperand(0));
@ -416,14 +416,14 @@ static SDValue GetNegatedExpression(SDValue Op, SelectionDAG &DAG,
case ISD::FDIV:
assert(!HonorSignDependentRoundingFPMath());
// -(X*Y) -> -X * Y
// fold (fneg (fmul X, Y)) -> (fmul (fneg X), Y)
if (isNegatibleForFree(Op.getOperand(0), LegalOperations, Depth+1))
return DAG.getNode(Op.getOpcode(), Op.getDebugLoc(), Op.getValueType(),
GetNegatedExpression(Op.getOperand(0), DAG,
LegalOperations, Depth+1),
Op.getOperand(1));
// -(X*Y) -> X * -Y
// fold (fneg (fmul X, Y)) -> (fmul X, (fneg Y))
return DAG.getNode(Op.getOpcode(), Op.getDebugLoc(), Op.getValueType(),
Op.getOperand(0),
GetNegatedExpression(Op.getOperand(1), DAG,