Commit 3dc7c5f7 authored by Craig Topper's avatar Craig Topper
Browse files

[LegalizeTypes] Remove code to create ISD::FP_TO_FP16 from SoftenFloatRes_FTRUNC. 

There seems to have been a misunderstanding of what ISD::FTRUNC
represents. ISD::FTRUNC is equivalent to llvm.trunc which takes
a floating point value, truncates it without changing the size
of the value and returns it.

Despite its similar name, its different than the fptrunc instruction
in IR which changes a floating point value to a smaller floating
point value. fptrunc is represented by ISD::FP_ROUND in SelectionDAG.

Since the ISD::FP_TO_FP16 node takes a floating point value and
converts it to f16 its more similar to ISD::FP_ROUND. In fact there
is identical code to what is being removed here in SoftenFloatRes_FP_ROUND.

I assume this bug was never encountered because it would require
f16 to be legalized by softening rather than the default of
promoting.
parent c43b8ec7

llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp

+0 −3
Original line number Diff line number Diff line
@@ -705,9 +705,6 @@ SDValue DAGTypeLegalizer::SoftenFloatRes_FSUB(SDNode *N) { 


SDValue DAGTypeLegalizer::SoftenFloatRes_FTRUNC(SDNode *N) {

  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));

  if (N->getValueType(0) == MVT::f16)

    return DAG.getNode(ISD::FP_TO_FP16, SDLoc(N), NVT, N->getOperand(0));



  SDValue Op = GetSoftenedFloat(N->getOperand(0));

  TargetLowering::MakeLibCallOptions CallOptions;

  EVT OpsVT[1] = { N->getOperand(0).getValueType() };