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[RISCV]: Implemented softening of FCANONICALIZE #169234

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[RISCV]: Implemented softening of FCANONICALIZE #169234

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a7af5b2
[RISCV]: Implemented softening of `FCANONICALIZE`
kper Nov 23, 2025
8aa7406
[RISCV]: Map to FMINIMUMNUM
kper Nov 24, 2025
08b567c
[RISCV]: Removed auto
kper Nov 26, 2025
1e3a036
[RISCV]: Use FMUL instead of fminimum_num
kper Nov 26, 2025
101a0ce
[DAG]: Copied fcanonicalize expansion to softening
kper Dec 3, 2025
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13 changes: 13 additions & 0 deletions llvm/lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,8 @@ void DAGTypeLegalizer::SoftenFloatResult(SDNode *N, unsigned ResNo) {
case ISD::EXTRACT_VECTOR_ELT:
R = SoftenFloatRes_EXTRACT_VECTOR_ELT(N, ResNo); break;
case ISD::FABS: R = SoftenFloatRes_FABS(N); break;
case ISD::FCANONICALIZE:
R = SoftenFloatRes_FCANONICALIZE(N); break;
case ISD::STRICT_FMINNUM:
case ISD::FMINNUM: R = SoftenFloatRes_FMINNUM(N); break;
case ISD::STRICT_FMAXNUM:
Expand Down Expand Up @@ -311,6 +313,17 @@ SDValue DAGTypeLegalizer::SoftenFloatRes_FABS(SDNode *N) {
return DAG.getNode(ISD::AND, SDLoc(N), NVT, Op, Mask);
}

SDValue DAGTypeLegalizer::SoftenFloatRes_FCANONICALIZE(SDNode *N) {
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@topperc topperc Dec 3, 2025

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This code feels like a series of hacks to reuse existing Softening functions.

Can we do this instead. It's the code from LegalizeDAG with a BitConvertToInteger at the end.

SDValue DAGTypeLegalizer::SoftenFloatRes_FCANONICALIZE(SDNode *N) {                                           
  SDLoc dl(N);                                                                                                
                                                                                                              
  // This implements llvm.canonicalize.f* by multiplication with 1.0, as
  // suggested in
  // https://llvm.org/docs/LangRef.html#llvm-canonicalize-intrinsic.
  // It uses strict_fp operations even outside a strict_fp context in order
  // to guarantee that the canonicalization is not optimized away by later
  // passes. The result chain introduced by that is intentionally ignored
  // since no ordering requirement is intended here.

  // Create strict multiplication by 1.0.
  SDValue Operand = N->getOperand(0);
  EVT VT = Operand.getValueType();
  SDValue One = DAG.getConstantFP(1.0, dl, VT);
  SDValue Chain = DAG.getEntryNode();
  // Propagate existing flags on canonicalize, and additionally set
  // NoFPExcept.
  SDNodeFlags CanonicalizeFlags = N->getFlags();
  CanonicalizeFlags.setNoFPExcept(true);
  SDValue Mul = DAG.getNode(ISD::STRICT_FMUL, dl, {VT, MVT::Other},
                            {Chain, Operand, One}, CanonicalizeFlags);
  return BitConvertToInteger(Mul);
}

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@kper kper Dec 3, 2025

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ah yes, thank you that's much better
you were right, I tried to bend the API to make it work like the other methods :)

SDLoc dl(N);
auto Node = DAG.getNode(ISD::FMINIMUMNUM, dl, N->getValueType(0),
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@arsenm arsenm Nov 24, 2025

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no auto

N->getOperand(0), N->getOperand(0));
return SoftenFloatRes_Binary(
Node.getNode(),
GetFPLibCall(N->getValueType(0), RTLIB::FMINIMUM_NUM_F32,
RTLIB::FMINIMUM_NUM_F64, RTLIB::FMINIMUM_NUM_F80,
RTLIB::FMINIMUM_NUM_F128, RTLIB::FMINIMUM_NUM_PPCF128));
}

SDValue DAGTypeLegalizer::SoftenFloatRes_FMINNUM(SDNode *N) {
if (SDValue SelCC = TLI.createSelectForFMINNUM_FMAXNUM(N, DAG))
return SoftenFloatRes_SELECT_CC(SelCC.getNode());
Expand Down
1 change: 1 addition & 0 deletions llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -585,6 +585,7 @@ class LLVM_LIBRARY_VISIBILITY DAGTypeLegalizer {
SDValue SoftenFloatRes_FASIN(SDNode *N);
SDValue SoftenFloatRes_FATAN(SDNode *N);
SDValue SoftenFloatRes_FATAN2(SDNode *N);
SDValue SoftenFloatRes_FCANONICALIZE(SDNode *N);
SDValue SoftenFloatRes_FMINNUM(SDNode *N);
SDValue SoftenFloatRes_FMAXNUM(SDNode *N);
SDValue SoftenFloatRes_FMINIMUMNUM(SDNode *N);
Expand Down
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