[LegalizeTypes] Remove untested code from ExpandIntOp_UINT_TO_FP

This code is untested in tree because the "APFloat::semanticsPrecision(sem) >= SrcVT.getSizeInBits() - 1" check is false for most combinations for int and fp types except maybe i32 and f64. For that you would need i32 to be an illegal type, but f64 to be legal and have custom handling for legalizing the split sint_to_fp. The precision check itself was added in 2010 to fix a double rounding issue in the algorithm that would occur if the sint_to_fp was not able to do the conversion without rounding.

Differential Revision: https://reviews.llvm.org/D72728

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

@@ -4153,82 +4153,14 @@ SDValue DAGTypeLegalizer::ExpandIntOp_UINT_TO_FP(SDNode *N) {
   bool IsStrict = N->isStrictFPOpcode();
   SDValue Chain = IsStrict ? N->getOperand(0) : SDValue();
   SDValue Op = N->getOperand(IsStrict ? 1 : 0);
-  EVT SrcVT = Op.getValueType();
   EVT DstVT = N->getValueType(0);
-  SDLoc dl(N);
-
-  // The following optimization is valid only if every value in SrcVT (when
-  // treated as signed) is representable in DstVT.  Check that the mantissa
-  // size of DstVT is >= than the number of bits in SrcVT -1.
-  const fltSemantics &sem = DAG.EVTToAPFloatSemantics(DstVT);
-  if (!IsStrict &&
-      APFloat::semanticsPrecision(sem) >= SrcVT.getSizeInBits() - 1 &&
-      TLI.getOperationAction(ISD::SINT_TO_FP, SrcVT) ==
-          TargetLowering::Custom) {
-    // Do a signed conversion then adjust the result.
-    SDValue SignedConv = DAG.getNode(ISD::SINT_TO_FP, dl, DstVT, Op);
-    SignedConv = TLI.LowerOperation(SignedConv, DAG);
-
-    // The result of the signed conversion needs adjusting if the 'sign bit' of
-    // the incoming integer was set.  To handle this, we dynamically test to see
-    // if it is set, and, if so, add a fudge factor.
-
-    const uint64_t F32TwoE32  = 0x4F800000ULL;
-    const uint64_t F32TwoE64  = 0x5F800000ULL;
-    const uint64_t F32TwoE128 = 0x7F800000ULL;
-
-    APInt FF(32, 0);
-    if (SrcVT == MVT::i32)
-      FF = APInt(32, F32TwoE32);
-    else if (SrcVT == MVT::i64)
-      FF = APInt(32, F32TwoE64);
-    else if (SrcVT == MVT::i128)
-      FF = APInt(32, F32TwoE128);
-    else
-      llvm_unreachable("Unsupported UINT_TO_FP!");
-
-    // Check whether the sign bit is set.
-    SDValue Lo, Hi;
-    GetExpandedInteger(Op, Lo, Hi);
-    SDValue SignSet = DAG.getSetCC(dl,
-                                   getSetCCResultType(Hi.getValueType()),
-                                   Hi,
-                                   DAG.getConstant(0, dl, Hi.getValueType()),
-                                   ISD::SETLT);
-
-    // Build a 64 bit pair (0, FF) in the constant pool, with FF in the lo bits.
-    SDValue FudgePtr =
-        DAG.getConstantPool(ConstantInt::get(*DAG.getContext(), FF.zext(64)),
-                            TLI.getPointerTy(DAG.getDataLayout()));
-
-    // Get a pointer to FF if the sign bit was set, or to 0 otherwise.
-    SDValue Zero = DAG.getIntPtrConstant(0, dl);
-    SDValue Four = DAG.getIntPtrConstant(4, dl);
-    if (DAG.getDataLayout().isBigEndian())
-      std::swap(Zero, Four);
-    SDValue Offset = DAG.getSelect(dl, Zero.getValueType(), SignSet,
-                                   Zero, Four);
-    unsigned Alignment = cast<ConstantPoolSDNode>(FudgePtr)->getAlignment();
-    FudgePtr = DAG.getMemBasePlusOffset(FudgePtr, Offset, dl);
-    Alignment = std::min(Alignment, 4u);
-
-    // Load the value out, extending it from f32 to the destination float type.
-    // FIXME: Avoid the extend by constructing the right constant pool?
-    SDValue Fudge = DAG.getExtLoad(
-        ISD::EXTLOAD, dl, DstVT, DAG.getEntryNode(), FudgePtr,
-        MachinePointerInfo::getConstantPool(DAG.getMachineFunction()), MVT::f32,
-        Alignment);
-    return DAG.getNode(ISD::FADD, dl, DstVT, SignedConv, Fudge);
-  }
-
-  // Otherwise, use a libcall.
-  RTLIB::Libcall LC = RTLIB::getUINTTOFP(SrcVT, DstVT);
+  RTLIB::Libcall LC = RTLIB::getUINTTOFP(Op.getValueType(), DstVT);
   assert(LC != RTLIB::UNKNOWN_LIBCALL &&
          "Don't know how to expand this UINT_TO_FP!");
   TargetLowering::MakeLibCallOptions CallOptions;
   CallOptions.setSExt(true);
   std::pair<SDValue, SDValue> Tmp =
-      TLI.makeLibCall(DAG, LC, DstVT, Op, CallOptions, dl, Chain);
+      TLI.makeLibCall(DAG, LC, DstVT, Op, CallOptions, SDLoc(N), Chain);
 
   if (!IsStrict)
     return Tmp.first;