Add support to promote f16 to f32

Summary:
This patch adds legalization support to operate on FP16 as a load/store type
and do operations on it as floats.

Tests for ARM are added to test/CodeGen/ARM/fp16-promote.ll

Reviewers: srhines, t.p.northover

Differential Revision: http://reviews.llvm.org/D8755

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235215 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetLowering.h

@@ -100,7 +100,8 @@ public:
     TypeExpandFloat,     // Split this float into two of half the size.
     TypeScalarizeVector, // Replace this one-element vector with its element.
     TypeSplitVector,     // Split this vector into two of half the size.
-    TypeWidenVector      // This vector should be widened into a larger vector.
+    TypeWidenVector,     // This vector should be widened into a larger vector.
+    TypePromoteFloat     // Replace this float with a larger one.
   };
 
   /// LegalizeKind holds the legalization kind that needs to happen to EVT

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -307,6 +307,7 @@ namespace {
     SDValue visitINSERT_SUBVECTOR(SDNode *N);
     SDValue visitMLOAD(SDNode *N);
     SDValue visitMSTORE(SDNode *N);
+    SDValue visitFP_TO_FP16(SDNode *N);
 
     SDValue XformToShuffleWithZero(SDNode *N);
     SDValue ReassociateOps(unsigned Opc, SDLoc DL, SDValue LHS, SDValue RHS);
@@ -1380,6 +1381,7 @@ SDValue DAGCombiner::visit(SDNode *N) {
   case ISD::INSERT_SUBVECTOR:   return visitINSERT_SUBVECTOR(N);
   case ISD::MLOAD:              return visitMLOAD(N);
   case ISD::MSTORE:             return visitMSTORE(N);
+  case ISD::FP_TO_FP16:         return visitFP_TO_FP16(N);
   }
   return SDValue();
 }
@@ -8161,6 +8163,11 @@ SDValue DAGCombiner::visitFP_EXTEND(SDNode *N) {
   if (isConstantFPBuildVectorOrConstantFP(N0))
     return DAG.getNode(ISD::FP_EXTEND, SDLoc(N), VT, N0);
 
+  // fold (fp_extend (fp16_to_fp op)) -> (fp16_to_fp op)
+  if (N0.getOpcode() == ISD::FP16_TO_FP &&
+      TLI.getOperationAction(ISD::FP16_TO_FP, VT) == TargetLowering::Legal)
+    return DAG.getNode(ISD::FP16_TO_FP, SDLoc(N), VT, N0.getOperand(0));
+
   // Turn fp_extend(fp_round(X, 1)) -> x since the fp_round doesn't affect the
   // value of X.
   if (N0.getOpcode() == ISD::FP_ROUND
@@ -12349,6 +12356,16 @@ SDValue DAGCombiner::visitINSERT_SUBVECTOR(SDNode *N) {
   return SDValue();
 }
 
+SDValue DAGCombiner::visitFP_TO_FP16(SDNode *N) {
+  SDValue N0 = N->getOperand(0);
+
+  // fold (fp_to_fp16 (fp16_to_fp op)) -> op
+  if (N0->getOpcode() == ISD::FP16_TO_FP)
+    return N0->getOperand(0);
+
+  return SDValue();
+}
+
 /// Returns a vector_shuffle if it able to transform an AND to a vector_shuffle
 /// with the destination vector and a zero vector.
 /// e.g. AND V, <0xffffffff, 0, 0xffffffff, 0>. ==>

lib/CodeGen/SelectionDAG/LegalizeFloatTypes.cpp

@@ -1579,3 +1579,420 @@ SDValue DAGTypeLegalizer::ExpandFloatOp_STORE(SDNode *N, unsigned OpNo) {
   return DAG.getTruncStore(Chain, SDLoc(N), Hi, Ptr,
                            ST->getMemoryVT(), ST->getMemOperand());
 }
+
+//===----------------------------------------------------------------------===//
+//  Float Operand Promotion
+//===----------------------------------------------------------------------===//
+//
+
+static ISD::NodeType GetPromotionOpcode(EVT OpVT, EVT RetVT) {
+  if (OpVT == MVT::f16) {
+      return ISD::FP16_TO_FP;
+  } else if (RetVT == MVT::f16) {
+      return ISD::FP_TO_FP16;
+  }
+
+  report_fatal_error("Attempt at an invalid promotion-related conversion");
+}
+
+bool DAGTypeLegalizer::PromoteFloatOperand(SDNode *N, unsigned OpNo) {
+  SDValue R = SDValue();
+
+  // Nodes that use a promotion-requiring floating point operand, but doesn't
+  // produce a promotion-requiring floating point result, need to be legalized
+  // to use the promoted float operand.  Nodes that produce at least one
+  // promotion-requiring floating point result have their operands legalized as
+  // a part of PromoteFloatResult.
+  switch (N->getOpcode()) {
+    default:
+      llvm_unreachable("Do not know how to promote this operator's operand!");
+
+    case ISD::BITCAST:    R = PromoteFloatOp_BITCAST(N, OpNo); break;
+    case ISD::FCOPYSIGN:  R = PromoteFloatOp_FCOPYSIGN(N, OpNo); break;
+    case ISD::FP_TO_SINT:
+    case ISD::FP_TO_UINT: R = PromoteFloatOp_FP_TO_XINT(N, OpNo); break;
+    case ISD::FP_EXTEND:  R = PromoteFloatOp_FP_EXTEND(N, OpNo); break;
+    case ISD::SELECT_CC:  R = PromoteFloatOp_SELECT_CC(N, OpNo); break;
+    case ISD::SETCC:      R = PromoteFloatOp_SETCC(N, OpNo); break;
+    case ISD::STORE:      R = PromoteFloatOp_STORE(N, OpNo); break;
+  }
+
+  if (R.getNode())
+    ReplaceValueWith(SDValue(N, 0), R);
+  return false;
+}
+
+SDValue DAGTypeLegalizer::PromoteFloatOp_BITCAST(SDNode *N, unsigned OpNo) {
+  SDValue Op = N->getOperand(0);
+  EVT OpVT = Op->getValueType(0);
+
+  EVT VT = N->getValueType(0);
+  EVT IVT = EVT::getIntegerVT(*DAG.getContext(), OpVT.getSizeInBits());
+  assert (IVT == VT && "Bitcast to type of different size");
+
+  SDValue Promoted = GetPromotedFloat(N->getOperand(0));
+  EVT PromotedVT = Promoted->getValueType(0);
+
+  // Convert the promoted float value to the desired IVT.
+  return DAG.getNode(GetPromotionOpcode(PromotedVT, OpVT), SDLoc(N), IVT,
+                     Promoted);
+}
+
+// Promote Operand 1 of FCOPYSIGN.  Operand 0 ought to be handled by
+// PromoteFloatRes_FCOPYSIGN.
+SDValue DAGTypeLegalizer::PromoteFloatOp_FCOPYSIGN(SDNode *N, unsigned OpNo) {
+  assert (OpNo == 1 && "Only Operand 1 must need promotion here");
+  SDValue Op1 = GetPromotedFloat(N->getOperand(1));
+
+  return DAG.getNode(N->getOpcode(), SDLoc(N), N->getValueType(0),
+                     N->getOperand(0), Op1);
+}
+
+// Convert the promoted float value to the desired integer type
+SDValue DAGTypeLegalizer::PromoteFloatOp_FP_TO_XINT(SDNode *N, unsigned OpNo) {
+  SDValue Op = GetPromotedFloat(N->getOperand(0));
+  return DAG.getNode(N->getOpcode(), SDLoc(N), N->getValueType(0), Op);
+}
+
+SDValue DAGTypeLegalizer::PromoteFloatOp_FP_EXTEND(SDNode *N, unsigned OpNo) {
+  SDValue Op = GetPromotedFloat(N->getOperand(0));
+  EVT VT = N->getValueType(0);
+
+  // Desired VT is same as promoted type.  Use promoted float directly.
+  if (VT == Op->getValueType(0))
+    return Op;
+
+  // Else, extend the promoted float value to the desired VT.
+  return DAG.getNode(ISD::FP_EXTEND, SDLoc(N), VT, Op);
+}
+
+// Promote the float operands used for comparison.  The true- and false-
+// operands have the same type as the result and are promoted, if needed, by
+// PromoteFloatRes_SELECT_CC
+SDValue DAGTypeLegalizer::PromoteFloatOp_SELECT_CC(SDNode *N, unsigned OpNo) {
+  SDValue LHS = GetPromotedFloat(N->getOperand(0));
+  SDValue RHS = GetPromotedFloat(N->getOperand(1));
+
+  return DAG.getNode(ISD::SELECT_CC, SDLoc(N), N->getValueType(0),
+                     LHS, RHS, N->getOperand(2), N->getOperand(3),
+                     N->getOperand(4));
+}
+
+// Construct a SETCC that compares the promoted values and sets the conditional
+// code.
+SDValue DAGTypeLegalizer::PromoteFloatOp_SETCC(SDNode *N, unsigned OpNo) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  SDValue Op0 = GetPromotedFloat(N->getOperand(0));
+  SDValue Op1 = GetPromotedFloat(N->getOperand(1));
+  ISD::CondCode CCCode = cast<CondCodeSDNode>(N->getOperand(2))->get();
+
+  return DAG.getSetCC(SDLoc(N), NVT, Op0, Op1, CCCode);
+
+}
+
+// Lower the promoted Float down to the integer value of same size and construct
+// a STORE of the integer value.
+SDValue DAGTypeLegalizer::PromoteFloatOp_STORE(SDNode *N, unsigned OpNo) {
+  StoreSDNode *ST = cast<StoreSDNode>(N);
+  SDValue Val = ST->getValue();
+  SDLoc DL(N);
+
+  SDValue Promoted = GetPromotedFloat(Val);
+  EVT VT = ST->getOperand(1)->getValueType(0);
+  EVT IVT = EVT::getIntegerVT(*DAG.getContext(), VT.getSizeInBits());
+
+  SDValue NewVal;
+  NewVal = DAG.getNode(GetPromotionOpcode(Promoted.getValueType(), VT), DL,
+                       IVT, Promoted);
+
+  return DAG.getStore(ST->getChain(), DL, NewVal, ST->getBasePtr(),
+                      ST->getMemOperand());
+}
+
+//===----------------------------------------------------------------------===//
+//  Float Result Promotion
+//===----------------------------------------------------------------------===//
+
+void DAGTypeLegalizer::PromoteFloatResult(SDNode *N, unsigned ResNo) {
+  SDValue R = SDValue();
+
+  switch (N->getOpcode()) {
+    // These opcodes cannot appear if promotion of FP16 is done in the backend
+    // instead of Clang
+    case ISD::FP16_TO_FP:
+    case ISD::FP_TO_FP16:
+    default:
+      llvm_unreachable("Do not know how to promote this operator's result!");
+
+    case ISD::BITCAST:    R = PromoteFloatRes_BITCAST(N); break;
+    case ISD::ConstantFP: R = PromoteFloatRes_ConstantFP(N); break;
+    case ISD::EXTRACT_VECTOR_ELT:
+                          R = PromoteFloatRes_EXTRACT_VECTOR_ELT(N); break;
+    case ISD::FCOPYSIGN:  R = PromoteFloatRes_FCOPYSIGN(N); break;
+
+    // Unary FP Operations
+    case ISD::FABS:
+    case ISD::FCEIL:
+    case ISD::FCOS:
+    case ISD::FEXP:
+    case ISD::FEXP2:
+    case ISD::FFLOOR:
+    case ISD::FLOG:
+    case ISD::FLOG2:
+    case ISD::FLOG10:
+    case ISD::FNEARBYINT:
+    case ISD::FNEG:
+    case ISD::FRINT:
+    case ISD::FROUND:
+    case ISD::FSIN:
+    case ISD::FSQRT:
+    case ISD::FTRUNC:     R = PromoteFloatRes_UnaryOp(N); break;
+
+    // Binary FP Operations
+    case ISD::FADD:
+    case ISD::FDIV:
+    case ISD::FMAXNUM:
+    case ISD::FMINNUM:
+    case ISD::FMUL:
+    case ISD::FPOW:
+    case ISD::FREM:
+    case ISD::FSUB:       R = PromoteFloatRes_BinOp(N); break;
+
+    case ISD::FMA:        // FMA is same as FMAD
+    case ISD::FMAD:       R = PromoteFloatRes_FMAD(N); break;
+
+    case ISD::FPOWI:      R = PromoteFloatRes_FPOWI(N); break;
+
+    case ISD::FP_ROUND:   R = PromoteFloatRes_FP_ROUND(N); break;
+    case ISD::LOAD:       R = PromoteFloatRes_LOAD(N); break;
+    case ISD::SELECT:     R = PromoteFloatRes_SELECT(N); break;
+    case ISD::SELECT_CC:  R = PromoteFloatRes_SELECT_CC(N); break;
+
+    case ISD::SINT_TO_FP:
+    case ISD::UINT_TO_FP: R = PromoteFloatRes_XINT_TO_FP(N); break;
+    case ISD::UNDEF:      R = PromoteFloatRes_UNDEF(N); break;
+
+  }
+
+  if (R.getNode())
+    SetPromotedFloat(SDValue(N, ResNo), R);
+}
+
+// Bitcast from i16 to f16:  convert the i16 to a f32 value instead.
+// At this point, it is not possible to determine if the bitcast value is
+// eventually stored to memory or promoted to f32 or promoted to a floating
+// point at a higher precision.  Some of these cases are handled by FP_EXTEND,
+// STORE promotion handlers.
+SDValue DAGTypeLegalizer::PromoteFloatRes_BITCAST(SDNode *N) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  return DAG.getNode(GetPromotionOpcode(VT, NVT), SDLoc(N), NVT,
+                     N->getOperand(0));
+}
+
+SDValue DAGTypeLegalizer::PromoteFloatRes_ConstantFP(SDNode *N) {
+  ConstantFPSDNode *CFPNode = cast<ConstantFPSDNode>(N);
+  EVT VT = N->getValueType(0);
+
+  // Get the (bit-cast) APInt of the APFloat and build an integer constant
+  EVT IVT = EVT::getIntegerVT(*DAG.getContext(), VT.getSizeInBits());
+  SDValue C = DAG.getConstant(CFPNode->getValueAPF().bitcastToAPInt(),
+                              IVT);
+
+  // Convert the Constant to the desired FP type
+  // FIXME We might be able to do the conversion during compilation and get rid
+  // of it from the object code
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  return DAG.getNode(GetPromotionOpcode(VT, NVT), SDLoc(N), NVT, C);
+}
+
+// If the Index operand is a constant, try to redirect the extract operation to
+// the correct legalized vector.  If not, bit-convert the input vector to
+// equivalent integer vector.  Extract the element as an (bit-cast) integer
+// value and convert it to the promoted type.
+SDValue DAGTypeLegalizer::PromoteFloatRes_EXTRACT_VECTOR_ELT(SDNode *N) {
+  SDLoc DL(N);
+
+  // If the index is constant, try to extract the value from the legalized
+  // vector type.
+  if (isa<ConstantSDNode>(N->getOperand(1))) {
+    SDValue Vec = N->getOperand(0);
+    SDValue Idx = N->getOperand(1);
+    EVT VecVT = Vec->getValueType(0);
+    EVT EltVT = VecVT.getVectorElementType();
+
+    uint64_t IdxVal = cast<ConstantSDNode>(Idx)->getZExtValue();
+
+    switch (getTypeAction(VecVT)) {
+    default: break;
+    case TargetLowering::TypeScalarizeVector: {
+      SDValue Res = GetScalarizedVector(N->getOperand(0));
+      ReplaceValueWith(SDValue(N, 0), Res);
+      return SDValue();
+    }
+    case TargetLowering::TypeWidenVector: {
+      Vec = GetWidenedVector(Vec);
+      SDValue Res = DAG.getNode(N->getOpcode(), DL, EltVT, Vec, Idx);
+      ReplaceValueWith(SDValue(N, 0), Res);
+      return SDValue();
+    }
+    case TargetLowering::TypeSplitVector: {
+      SDValue Lo, Hi;
+      GetSplitVector(Vec, Lo, Hi);
+
+      uint64_t LoElts = Lo.getValueType().getVectorNumElements();
+      SDValue Res;
+      if (IdxVal < LoElts)
+        Res = DAG.getNode(N->getOpcode(), DL, EltVT, Lo, Idx);
+      else
+        Res = DAG.getNode(N->getOpcode(), DL, EltVT, Hi,
+                          DAG.getConstant(IdxVal - LoElts,
+                                          Idx.getValueType()));
+      ReplaceValueWith(SDValue(N, 0), Res);
+      return SDValue();
+    }
+
+    }
+  }
+
+  // Bit-convert the input vector to the equivalent integer vector
+  SDValue NewOp = BitConvertVectorToIntegerVector(N->getOperand(0));
+  EVT IVT = NewOp.getValueType().getVectorElementType();
+
+  // Extract the element as an (bit-cast) integer value
+  SDValue NewVal = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, IVT,
+                               NewOp, N->getOperand(1));
+
+  // Convert the element to the desired FP type
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  return DAG.getNode(GetPromotionOpcode(VT, NVT), SDLoc(N), NVT, NewVal);
+}
+
+// FCOPYSIGN(X, Y) returns the value of X with the sign of Y.  If the result
+// needs promotion, so does the argument X.  Note that Y, if needed, will be
+// handled during operand promotion.
+SDValue DAGTypeLegalizer::PromoteFloatRes_FCOPYSIGN(SDNode *N) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  SDValue Op0 = GetPromotedFloat(N->getOperand(0));
+
+  SDValue Op1 = N->getOperand(1);
+
+  return DAG.getNode(N->getOpcode(), SDLoc(N), NVT, Op0, Op1);
+}
+
+// Unary operation where the result and the operand have PromoteFloat type
+// action.  Construct a new SDNode with the promoted float value of the old
+// operand.
+SDValue DAGTypeLegalizer::PromoteFloatRes_UnaryOp(SDNode *N) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  SDValue Op = GetPromotedFloat(N->getOperand(0));
+
+  return DAG.getNode(N->getOpcode(), SDLoc(N), NVT, Op);
+}
+
+// Binary operations where the result and both operands have PromoteFloat type
+// action.  Construct a new SDNode with the promoted float values of the old
+// operands.
+SDValue DAGTypeLegalizer::PromoteFloatRes_BinOp(SDNode *N) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  SDValue Op0 = GetPromotedFloat(N->getOperand(0));
+  SDValue Op1 = GetPromotedFloat(N->getOperand(1));
+
+  return DAG.getNode(N->getOpcode(), SDLoc(N), NVT, Op0, Op1);
+}
+
+SDValue DAGTypeLegalizer::PromoteFloatRes_FMAD(SDNode *N) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  SDValue Op0 = GetPromotedFloat(N->getOperand(0));
+  SDValue Op1 = GetPromotedFloat(N->getOperand(1));
+  SDValue Op2 = GetPromotedFloat(N->getOperand(2));
+
+  return DAG.getNode(N->getOpcode(), SDLoc(N), NVT, Op0, Op1, Op2);
+}
+
+// Promote the Float (first) operand and retain the Integer (second) operand
+SDValue DAGTypeLegalizer::PromoteFloatRes_FPOWI(SDNode *N) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  SDValue Op0 = GetPromotedFloat(N->getOperand(0));
+  SDValue Op1 = N->getOperand(1);
+
+  return DAG.getNode(N->getOpcode(), SDLoc(N), NVT, Op0, Op1);
+}
+
+// Explicit operation to reduce precision.  Reduce the value to half precision
+// and promote it back to the legal type.
+SDValue DAGTypeLegalizer::PromoteFloatRes_FP_ROUND(SDNode *N) {
+  SDLoc DL(N);
+
+  SDValue Op = N->getOperand(0);
+  EVT VT = N->getValueType(0);
+  EVT OpVT = Op->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
+  EVT IVT = EVT::getIntegerVT(*DAG.getContext(), VT.getSizeInBits());
+
+  // Round promoted float to desired precision
+  SDValue Round = DAG.getNode(GetPromotionOpcode(OpVT, VT), DL, IVT, Op);
+  // Promote it back to the legal output type
+  return DAG.getNode(GetPromotionOpcode(VT, NVT), DL, NVT, Round);
+}
+
+SDValue DAGTypeLegalizer::PromoteFloatRes_LOAD(SDNode *N) {
+  LoadSDNode *L = cast<LoadSDNode>(N);
+  EVT VT = N->getValueType(0);
+
+  // Load the value as an integer value with the same number of bits
+  EVT IVT = EVT::getIntegerVT(*DAG.getContext(), VT.getSizeInBits());
+  SDValue newL = DAG.getLoad(L->getAddressingMode(), L->getExtensionType(),
+                   IVT, SDLoc(N), L->getChain(), L->getBasePtr(),
+                   L->getOffset(), L->getPointerInfo(), IVT, L->isVolatile(),
+                   L->isNonTemporal(), false, L->getAlignment(),
+                   L->getAAInfo());
+  // Legalize the chain result by replacing uses of the old value chain with the
+  // new one
+  ReplaceValueWith(SDValue(N, 1), newL.getValue(1));
+
+  // Convert the integer value to the desired FP type
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  return DAG.getNode(GetPromotionOpcode(VT, NVT), SDLoc(N), NVT, newL);
+}
+
+// Construct a new SELECT node with the promoted true- and false- values.
+SDValue DAGTypeLegalizer::PromoteFloatRes_SELECT(SDNode *N) {
+  SDValue TrueVal = GetPromotedFloat(N->getOperand(1));
+  SDValue FalseVal = GetPromotedFloat(N->getOperand(2));
+
+  return DAG.getNode(ISD::SELECT, SDLoc(N), TrueVal->getValueType(0),
+                     N->getOperand(0), TrueVal, FalseVal);
+}
+
+// Construct a new SELECT_CC node with the promoted true- and false- values.
+// The operands used for comparison are promoted by PromoteFloatOp_SELECT_CC.
+SDValue DAGTypeLegalizer::PromoteFloatRes_SELECT_CC(SDNode *N) {
+  SDValue TrueVal = GetPromotedFloat(N->getOperand(2));
+  SDValue FalseVal = GetPromotedFloat(N->getOperand(3));
+
+  return DAG.getNode(ISD::SELECT_CC, SDLoc(N), N->getValueType(0),
+                     N->getOperand(0), N->getOperand(1), TrueVal, FalseVal,
+                     N->getOperand(4));
+}
+
+// Construct a SDNode that transforms the SINT or UINT operand to the promoted
+// float type.
+SDValue DAGTypeLegalizer::PromoteFloatRes_XINT_TO_FP(SDNode *N) {
+  EVT VT = N->getValueType(0);
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), VT);
+  return DAG.getNode(N->getOpcode(), SDLoc(N), NVT, N->getOperand(0));
+}
+
+SDValue DAGTypeLegalizer::PromoteFloatRes_UNDEF(SDNode *N) {
+  return DAG.getUNDEF(TLI.getTypeToTransformTo(*DAG.getContext(),
+                                               N->getValueType(0)));
+}
+

lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

@@ -251,6 +251,16 @@ SDValue DAGTypeLegalizer::PromoteIntRes_BITCAST(SDNode *N) {
   case TargetLowering::TypeSoftenFloat:
     // Promote the integer operand by hand.
     return DAG.getNode(ISD::ANY_EXTEND, dl, NOutVT, GetSoftenedFloat(InOp));
+  case TargetLowering::TypePromoteFloat: {
+    // Convert the promoted float by hand.
+    if (NOutVT.bitsEq(NInVT)) {
+      SDValue PromotedOp = GetPromotedFloat(InOp);
+      SDValue Trunc = DAG.getNode(ISD::FP_TO_FP16, dl, NOutVT, PromotedOp);
+      return DAG.getNode(ISD::AssertZext, dl, NOutVT, Trunc,
+                         DAG.getValueType(OutVT));
+    }
+    break;
+  }
   case TargetLowering::TypeExpandInteger:
   case TargetLowering::TypeExpandFloat:
     break;
@@ -1845,7 +1855,11 @@ 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);
+
   RTLIB::Libcall LC = RTLIB::getFPTOSINT(Op.getValueType(), VT);
   assert(LC != RTLIB::UNKNOWN_LIBCALL && "Unexpected fp-to-sint conversion!");
   SplitInteger(TLI.makeLibCall(DAG, LC, VT, &Op, 1, true/*irrelevant*/,
@@ -1857,7 +1871,11 @@ void DAGTypeLegalizer::ExpandIntRes_FP_TO_UINT(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);
+
   RTLIB::Libcall LC = RTLIB::getFPTOUINT(Op.getValueType(), VT);
   assert(LC != RTLIB::UNKNOWN_LIBCALL && "Unexpected fp-to-uint conversion!");
   SplitInteger(TLI.makeLibCall(DAG, LC, VT, &Op, 1, false/*irrelevant*/,

lib/CodeGen/SelectionDAG/LegalizeTypes.cpp

@@ -259,6 +259,10 @@ bool DAGTypeLegalizer::run() {
         WidenVectorResult(N, i);
         Changed = true;
         goto NodeDone;
+      case TargetLowering::TypePromoteFloat:
+        PromoteFloatResult(N, i);
+        Changed = true;
+        goto NodeDone;
       }
     }
 
@@ -308,6 +312,10 @@ ScanOperands:
         NeedsReanalyzing = WidenVectorOperand(N, i);
         Changed = true;
         break;
+      case TargetLowering::TypePromoteFloat:
+        NeedsReanalyzing = PromoteFloatOperand(N, i);
+        Changed = true;
+        break;
       }
       break;
     }
@@ -753,6 +761,17 @@ void DAGTypeLegalizer::SetSoftenedFloat(SDValue Op, SDValue Result) {
   OpEntry = Result;
 }
 
+void DAGTypeLegalizer::SetPromotedFloat(SDValue Op, SDValue Result) {
+  assert(Result.getValueType() ==
+         TLI.getTypeToTransformTo(*DAG.getContext(), Op.getValueType()) &&
+         "Invalid type for promoted float");
+  AnalyzeNewValue(Result);
+
+  SDValue &OpEntry = PromotedFloats[Op];
+  assert(!OpEntry.getNode() && "Node is already promoted!");
+  OpEntry = Result;
+}
+
 void DAGTypeLegalizer::SetScalarizedVector(SDValue Op, SDValue Result) {
   // Note that in some cases vector operation operands may be greater than
   // the vector element type. For example BUILD_VECTOR of type <1 x i1> with

lib/CodeGen/SelectionDAG/LegalizeTypes.h

@@ -93,6 +93,11 @@ private:
   /// the same size, this map indicates the converted value to use.
   SmallDenseMap<SDValue, SDValue, 8> SoftenedFloats;
 
+  /// PromotedFloats - For floating point nodes that have a smaller precision
+  /// than the smallest supported precision, this map indicates what promoted
+  /// value to use.
+  SmallDenseMap<SDValue, SDValue, 8> PromotedFloats;
+
   /// ExpandedFloats - For float nodes that need to be expanded this map
   /// indicates which operands are the expanded version of the input.
   SmallDenseMap<SDValue, std::pair<SDValue, SDValue>, 8> ExpandedFloats;
@@ -499,6 +504,44 @@ private:
   void FloatExpandSetCCOperands(SDValue &NewLHS, SDValue &NewRHS,
                                 ISD::CondCode &CCCode, SDLoc dl);
 
+
+  //===--------------------------------------------------------------------===//
+  // Float promotion support: LegalizeFloatTypes.cpp
+  //===--------------------------------------------------------------------===//
+
+  SDValue GetPromotedFloat(SDValue Op) {
+    SDValue &PromotedOp = PromotedFloats[Op];
+    RemapValue(PromotedOp);
+    assert(PromotedOp.getNode() && "Operand wasn't promoted?");
+    return PromotedOp;
+  }
+  void SetPromotedFloat(SDValue Op, SDValue Result);
+
+  void PromoteFloatResult(SDNode *N, unsigned ResNo);
+  SDValue PromoteFloatRes_BITCAST(SDNode *N);
+  SDValue PromoteFloatRes_BinOp(SDNode *N);
+  SDValue PromoteFloatRes_ConstantFP(SDNode *N);
+  SDValue PromoteFloatRes_EXTRACT_VECTOR_ELT(SDNode *N);
+  SDValue PromoteFloatRes_FCOPYSIGN(SDNode *N);
+  SDValue PromoteFloatRes_FMAD(SDNode *N);
+  SDValue PromoteFloatRes_FPOWI(SDNode *N);
+  SDValue PromoteFloatRes_FP_ROUND(SDNode *N);
+  SDValue PromoteFloatRes_LOAD(SDNode *N);
+  SDValue PromoteFloatRes_SELECT(SDNode *N);
+  SDValue PromoteFloatRes_SELECT_CC(SDNode *N);
+  SDValue PromoteFloatRes_UnaryOp(SDNode *N);
+  SDValue PromoteFloatRes_UNDEF(SDNode *N);
+  SDValue PromoteFloatRes_XINT_TO_FP(SDNode *N);
+
+  bool PromoteFloatOperand(SDNode *N, unsigned ResNo);
+  SDValue PromoteFloatOp_BITCAST(SDNode *N, unsigned OpNo);
+  SDValue PromoteFloatOp_FCOPYSIGN(SDNode *N, unsigned OpNo);
+  SDValue PromoteFloatOp_FP_EXTEND(SDNode *N, unsigned OpNo);
+  SDValue PromoteFloatOp_FP_TO_XINT(SDNode *N, unsigned OpNo);
+  SDValue PromoteFloatOp_STORE(SDNode *N, unsigned OpNo);
+  SDValue PromoteFloatOp_SELECT_CC(SDNode *N, unsigned OpNo);
+  SDValue PromoteFloatOp_SETCC(SDNode *N, unsigned OpNo);
+
   //===--------------------------------------------------------------------===//
   // Scalarization Support: LegalizeVectorTypes.cpp
   //===--------------------------------------------------------------------===//

lib/CodeGen/TargetLoweringBase.cpp

@@ -1256,10 +1256,19 @@ void TargetLoweringBase::computeRegisterProperties(
   }
 
   if (!isTypeLegal(MVT::f16)) {
-    NumRegistersForVT[MVT::f16] = NumRegistersForVT[MVT::i16];
-    RegisterTypeForVT[MVT::f16] = RegisterTypeForVT[MVT::i16];
-    TransformToType[MVT::f16] = MVT::i16;
-    ValueTypeActions.setTypeAction(MVT::f16, TypeSoftenFloat);
+    // If the target has native f32 support, promote f16 operations to f32.  If
+    // f32 is not supported, generate soft float library calls.
+    if (isTypeLegal(MVT::f32)) {
+      NumRegistersForVT[MVT::f16] = NumRegistersForVT[MVT::f32];
+      RegisterTypeForVT[MVT::f16] = RegisterTypeForVT[MVT::f32];
+      TransformToType[MVT::f16] = MVT::f32;
+      ValueTypeActions.setTypeAction(MVT::f16, TypePromoteFloat);
+    } else {
+      NumRegistersForVT[MVT::f16] = NumRegistersForVT[MVT::i16];
+      RegisterTypeForVT[MVT::f16] = RegisterTypeForVT[MVT::i16];
+      TransformToType[MVT::f16] = MVT::i16;
+      ValueTypeActions.setTypeAction(MVT::f16, TypeSoftenFloat);
+    }
   }
 
   // Loop over all of the vector value types to see which need transformations.