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-rw-r--r--llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp26
1 files changed, 15 insertions, 11 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 24ab65171a17..368e2100031f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5490,9 +5490,20 @@ char TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
EVT VT = Op.getValueType();
const SDNodeFlags Flags = Op->getFlags();
const TargetOptions &Options = DAG.getTarget().Options;
- if (!Op.hasOneUse() && !(Op.getOpcode() == ISD::FP_EXTEND &&
- isFPExtFree(VT, Op.getOperand(0).getValueType())))
- return 0;
+ if (!Op.hasOneUse()) {
+ bool IsFreeExtend = Op.getOpcode() == ISD::FP_EXTEND &&
+ isFPExtFree(VT, Op.getOperand(0).getValueType());
+
+ // If we already have the use of the negated floating constant, it is free
+ // to negate it even it has multiple uses.
+ bool IsFreeConstant =
+ Op.getOpcode() == ISD::ConstantFP &&
+ !getNegatedExpression(Op, DAG, LegalOperations, ForCodeSize)
+ .use_empty();
+
+ if (!IsFreeExtend && !IsFreeConstant)
+ return 0;
+ }
// Don't recurse exponentially.
if (Depth > SelectionDAG::MaxRecursionDepth)
@@ -5687,14 +5698,7 @@ SDValue TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
ForCodeSize, Depth + 1);
char V1 = isNegatibleForFree(Op.getOperand(1), DAG, LegalOperations,
ForCodeSize, Depth + 1);
- // TODO: This is a hack. It is possible that costs have changed between now
- // and the initial calls to isNegatibleForFree(). That is because we
- // are rewriting the expression, and that may change the number of
- // uses (and therefore the cost) of values. If the negation costs are
- // equal, only negate this value if it is a constant. Otherwise, try
- // operand 1. A better fix would eliminate uses as a cost factor or
- // track the change in uses as we rewrite the expression.
- if (V0 > V1 || (V0 == V1 && isa<ConstantFPSDNode>(Op.getOperand(0)))) {
+ if (V0 > V1) {
// fold (fneg (fma X, Y, Z)) -> (fma (fneg X), Y, (fneg Z))
SDValue Neg0 = getNegatedExpression(
Op.getOperand(0), DAG, LegalOperations, ForCodeSize, Depth + 1);