Changes in directory llvm/lib/CodeGen/SelectionDAG:
LegalizeDAG.cpp updated: 1.313 -> 1.314
---
Log message:
For targets with FABS/FNEG support, lower copysign to an integer load,
a select and FABS/FNEG.
This speeds up a trivial (aka stupid) copysign benchmark I wrote from 6.73s
to 2.64s, woo.
---
Diffs of the changes: (+25 -2)
LegalizeDAG.cpp | 27 +++++++++++++++++++++++++--
1 files changed, 25 insertions(+), 2 deletions(-)
Index: llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:1.313
llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:1.314
--- llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp:1.313 Tue Mar 7 22:39:05 2006
+++ llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp Mon Mar 13 00:08:38 2006
@@ -1795,10 +1795,33 @@
case TargetLowering::Custom:
Tmp1 = TLI.LowerOperation(Result, DAG);
if (Tmp1.Val) Result = Tmp1;
- break;
+ break;
case TargetLowering::Legal: break;
case TargetLowering::Expand:
- // Floating point mod -> fmod libcall.
+ // If this target supports fabs/fneg natively, do this efficiently.
+ if (TLI.isOperationLegal(ISD::FABS, Tmp1.getValueType()) &&
+ TLI.isOperationLegal(ISD::FNEG, Tmp1.getValueType())) {
+ // Get the sign bit of the RHS.
+ MVT::ValueType IVT =
+ Tmp2.getValueType() == MVT::f32 ? MVT::i32 : MVT::i64;
+ SDOperand SignBit = DAG.getNode(ISD::BIT_CONVERT, IVT, Tmp2);
+ SignBit = DAG.getSetCC(TLI.getSetCCResultTy(),
+ SignBit, DAG.getConstant(0, IVT), ISD::SETLT);
+ // Get the absolute value of the result.
+ SDOperand AbsVal = DAG.getNode(ISD::FABS, Tmp1.getValueType(), Tmp1);
+ // Select between the nabs and abs value based on the sign bit of
+ // the input.
+ Result = DAG.getNode(ISD::SELECT, AbsVal.getValueType(), SignBit,
+ DAG.getNode(ISD::FNEG, AbsVal.getValueType(),
+ AbsVal),
+ AbsVal);
+ Result = LegalizeOp(Result);
+ break;
+ }
+
+ // Otherwise, do bitwise ops!
+
+ // copysign -> copysignf/copysign libcall.
const char *FnName;
if (Node->getValueType(0) == MVT::f32) {
FnName = "copysignf";
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