[SelectionDAGBuilder] Support llvm.flt.rounds on targets where i32 is not legal

[edward-jones]

Summary

Add integer expansion for FLT_ROUNDS_ for targets where i32 is not a legal type.

[edward-jones]

Ping.

[hfinkel]

Why don't we create it with i32 during SDAG building and then legalize the type later during type legalization (i.e. add handling in DAGTypeLegalizer::ExpandIntegerResult)?

[edward-jones]

hfinkel, Yes I guess that's probably a better approach. I've updated the patch to add ExpandIntRes_FLT_ROUNDS to do this.

[hfinkel]

LGTM.

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

2029

Please add a comment here that you're sign-extending the high part because the value might be -1.

[edward-jones]

Added a comment, and re-add the msp430 test from the first patch.

If this is acceptable, is it okay for someone to commit this on my behalf.

[hfinkel]

r283797.

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

#endif
   case ISD::BITREVERSE:  ExpandIntRes_BITREVERSE(N, Lo, Hi); break;
   case ISD::BSWAP:       ExpandIntRes_BSWAP(N, Lo, Hi); break;
   case ISD::Constant:    ExpandIntRes_Constant(N, Lo, Hi); break;
   case ISD::CTLZ_ZERO_UNDEF:
   case ISD::CTLZ:        ExpandIntRes_CTLZ(N, Lo, Hi); break;
   case ISD::CTPOP:       ExpandIntRes_CTPOP(N, Lo, Hi); break;
   case ISD::CTTZ_ZERO_UNDEF:
   case ISD::CTTZ:        ExpandIntRes_CTTZ(N, Lo, Hi); break;
+  case ISD::FLT_ROUNDS_: ExpandIntRes_FLT_ROUNDS(N, Lo, Hi); break;
   case ISD::FP_TO_SINT:  ExpandIntRes_FP_TO_SINT(N, Lo, Hi); break;
   case ISD::FP_TO_UINT:  ExpandIntRes_FP_TO_UINT(N, Lo, Hi); break;
   case ISD::LOAD:        ExpandIntRes_LOAD(cast<LoadSDNode>(N), Lo, Hi); break;
   case ISD::MUL:         ExpandIntRes_MUL(N, Lo, Hi); break;
   case ISD::READCYCLECOUNTER: ExpandIntRes_READCYCLECOUNTER(N, Lo, Hi); break;
   case ISD::SDIV:        ExpandIntRes_SDIV(N, Lo, Hi); break;
   case ISD::SIGN_EXTEND: ExpandIntRes_SIGN_EXTEND(N, Lo, Hi); break;
   case ISD::SIGN_EXTEND_INREG: ExpandIntRes_SIGN_EXTEND_INREG(N, Lo, Hi); break;
void DAGTypeLegalizer::ExpandIntRes_CTTZ(SDNode *N,
 
   Lo = DAG.getSelect(dl, NVT, LoNotZero, LoLZ,
                      DAG.getNode(ISD::ADD, dl, NVT, HiLZ,
                                  DAG.getConstant(NVT.getSizeInBits(), dl,
                                                  NVT)));
   Hi = DAG.getConstant(0, dl, NVT);
 }
 
+void DAGTypeLegalizer::ExpandIntRes_FLT_ROUNDS(SDNode *N, SDValue &Lo,
+                                               SDValue &Hi) {
+  SDLoc dl(N);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
+  unsigned NBitWidth = NVT.getSizeInBits();
+
+  EVT ShiftAmtTy = TLI.getShiftAmountTy(NVT, DAG.getDataLayout());
+  Lo = DAG.getNode(ISD::FLT_ROUNDS_, dl, NVT);
+  // The high part is the sign of Lo, as -1 is a valid value for FLT_ROUNDS
+  Hi = DAG.getNode(ISD::SRA, dl, NVT, Lo,
+                   DAG.getConstant(NBitWidth - 1, dl, ShiftAmtTy));
+}
+
 void DAGTypeLegalizer::ExpandIntRes_FP_TO_SINT(SDNode *N, SDValue &Lo,
                                                SDValue &Hi) {
   SDLoc dl(N);
   EVT VT = N->getValueType(0);
 
   SDValue Op = N->getOperand(0);
   if (getTypeAction(Op.getValueType()) == TargetLowering::TypePromoteFloat)
     Op = GetPromotedFloat(Op);

lib/CodeGen/SelectionDAG/LegalizeTypes.h

private:
   void ExpandIntRes_CTPOP             (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_CTTZ              (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_LOAD          (LoadSDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_READCYCLECOUNTER  (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_SIGN_EXTEND       (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_SIGN_EXTEND_INREG (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_TRUNCATE          (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_ZERO_EXTEND       (SDNode *N, SDValue &Lo, SDValue &Hi);
+  void ExpandIntRes_FLT_ROUNDS        (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_FP_TO_SINT        (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_FP_TO_UINT        (SDNode *N, SDValue &Lo, SDValue &Hi);
 
   void ExpandIntRes_Logical           (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_ADDSUB            (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_ADDSUBC           (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_ADDSUBE           (SDNode *N, SDValue &Lo, SDValue &Hi);
   void ExpandIntRes_BITREVERSE        (SDNode *N, SDValue &Lo, SDValue &Hi);

test/CodeGen/MSP430/flt_rounds.ll

+; RUN: llc -verify-machineinstrs < %s -march=msp430
+
+define i16 @foo() {
+entry:
+  %0 = call i32 @llvm.flt.rounds()
+  %1 = trunc i32 %0 to i16
+  ret i16 %1
+}
+
+declare i32 @llvm.flt.rounds() nounwind