[FPEnv] Add fptosi and fptoui constrained intrinsics.

This implements constrained floating point intrinsics for FP to signed and
unsigned integers.

Quoting from D32319:
The purpose of the constrained intrinsics is to force the optimizer to
respect the restrictions that will be necessary to support things like the
STDC FENV_ACCESS ON pragma without interfering with optimizations when
these restrictions are not needed.

Reviewed by:	Andrew Kaylor, Craig Topper, Hal Finkel, Cameron McInally, Roman Lebedev, Kit Barton
Approved by:	Craig Topper
Differential Revision:	http://reviews.llvm.org/D63782

llvm-svn: 370228

llvm/docs/LangRef.rst

@@ -15280,6 +15280,72 @@ The result produced is the product of the first two operands added to the third
 operand computed with infinite precision, and then rounded to the target
 precision.
 
+'``llvm.experimental.constrained.fptoui``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare <ty2>
+      @llvm.experimental.constrained.fptoui(<type> <value>,
+                                          metadata <exception behavior>)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.constrained.fptoui``' intrinsic converts a 
+floating-point ``value`` to its unsigned integer equivalent of type ``ty2``.
+
+Arguments:
+""""""""""
+
+The first argument to the '``llvm.experimental.constrained.fptoui``'
+intrinsic must be :ref:`floating point <t_floating>` or :ref:`vector
+<t_vector>` of floating point values.
+
+The second argument specifies the exception behavior as described above.
+
+Semantics:
+""""""""""
+
+The result produced is an unsigned integer converted from the floating
+point operand. The value is truncated, so it is rounded towards zero.
+
+'``llvm.experimental.constrained.fptosi``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+::
+
+      declare <ty2>
+      @llvm.experimental.constrained.fptosi(<type> <value>,
+                                          metadata <exception behavior>)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.constrained.fptosi``' intrinsic converts 
+:ref:`floating-point <t_floating>` ``value`` to type ``ty2``.
+
+Arguments:
+""""""""""
+
+The first argument to the '``llvm.experimental.constrained.fptosi``'
+intrinsic must be :ref:`floating point <t_floating>` or :ref:`vector
+<t_vector>` of floating point values. 
+
+The second argument specifies the exception behavior as described above.
+
+Semantics:
+""""""""""
+
+The result produced is a signed integer converted from the floating
+point operand. The value is truncated, so it is rounded towards zero.
+
 '``llvm.experimental.constrained.fptrunc``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

llvm/include/llvm/CodeGen/ISDOpcodes.h

@@ -302,6 +302,13 @@ namespace ISD {
     STRICT_FRINT, STRICT_FNEARBYINT, STRICT_FMAXNUM, STRICT_FMINNUM,
     STRICT_FCEIL, STRICT_FFLOOR, STRICT_FROUND, STRICT_FTRUNC,
 
+    /// STRICT_FP_TO_[US]INT - Convert a floating point value to a signed or
+    /// unsigned integer. These have the same semantics as fptosi and fptoui 
+    /// in IR.
+    /// They are used to limit optimizations while the DAG is being optimized.
+    STRICT_FP_TO_SINT,
+    STRICT_FP_TO_UINT,
+
     /// X = STRICT_FP_ROUND(Y, TRUNC) - Rounding 'Y' from a larger floating 
     /// point type down to the precision of the destination VT.  TRUNC is a 
     /// flag, which is always an integer that is zero or one.  If TRUNC is 0,

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

@@ -709,6 +709,8 @@ END_TWO_BYTE_PACK()
       case ISD::STRICT_FFLOOR:
       case ISD::STRICT_FROUND:
       case ISD::STRICT_FTRUNC:
+      case ISD::STRICT_FP_TO_SINT:
+      case ISD::STRICT_FP_TO_UINT:
       case ISD::STRICT_FP_ROUND:
       case ISD::STRICT_FP_EXTEND:
         return true;

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -960,6 +960,8 @@ class TargetLoweringBase {
       case ISD::STRICT_FFLOOR: EqOpc = ISD::FFLOOR; break;
       case ISD::STRICT_FROUND: EqOpc = ISD::FROUND; break;
       case ISD::STRICT_FTRUNC: EqOpc = ISD::FTRUNC; break;
+      case ISD::STRICT_FP_TO_SINT: EqOpc = ISD::FP_TO_SINT; break;
+      case ISD::STRICT_FP_TO_UINT: EqOpc = ISD::FP_TO_UINT; break;
       case ISD::STRICT_FP_ROUND: EqOpc = ISD::FP_ROUND; break;
       case ISD::STRICT_FP_EXTEND: EqOpc = ISD::FP_EXTEND; break;
     }
@@ -3999,7 +4001,7 @@ class TargetLowering : public TargetLoweringBase {
   /// \param N Node to expand
   /// \param Result output after conversion
   /// \returns True, if the expansion was successful, false otherwise
-  bool expandFP_TO_UINT(SDNode *N, SDValue &Result, SelectionDAG &DAG) const;
+  bool expandFP_TO_UINT(SDNode *N, SDValue &Result, SDValue &Chain, SelectionDAG &DAG) const;
 
   /// Expand UINT(i64) to double(f64) conversion
   /// \param N Node to expand

llvm/include/llvm/IR/IntrinsicInst.h

@@ -259,6 +259,8 @@ namespace llvm {
       case Intrinsic::experimental_constrained_fdiv:
       case Intrinsic::experimental_constrained_frem:
       case Intrinsic::experimental_constrained_fma:
+      case Intrinsic::experimental_constrained_fptosi:
+      case Intrinsic::experimental_constrained_fptoui:
       case Intrinsic::experimental_constrained_fptrunc:
       case Intrinsic::experimental_constrained_fpext:
       case Intrinsic::experimental_constrained_sqrt:

llvm/include/llvm/IR/Intrinsics.td

@@ -622,6 +622,14 @@ let IntrProperties = [IntrInaccessibleMemOnly, IntrWillReturn] in {
                                                       llvm_metadata_ty,
                                                       llvm_metadata_ty ]>;
 
+  def int_experimental_constrained_fptosi : Intrinsic<[ llvm_anyint_ty ],
+                                                    [ llvm_anyfloat_ty,
+                                                      llvm_metadata_ty ]>;
+
+  def int_experimental_constrained_fptoui : Intrinsic<[ llvm_anyint_ty ],
+                                                    [ llvm_anyfloat_ty,
+                                                      llvm_metadata_ty ]>;
+
   def int_experimental_constrained_fptrunc : Intrinsic<[ llvm_anyfloat_ty ],
                                                        [ llvm_anyfloat_ty,
                                                          llvm_metadata_ty,
@@ -712,7 +720,8 @@ let IntrProperties = [IntrInaccessibleMemOnly, IntrWillReturn] in {
                                                        llvm_metadata_ty,
                                                        llvm_metadata_ty ]>;
 }
-// FIXME: Add intrinsics for fcmp, fptoui and fptosi.
+// FIXME: Add intrinsic for fcmp.
+// FIXME: Consider maybe adding intrinsics for sitofp, uitofp.
 
 //===------------------------- Expect Intrinsics --------------------------===//
 //

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -236,6 +236,16 @@ class SelectionDAGLegalize {
     }
     ReplacedNode(Old);
   }
+
+  void ReplaceNodeWithValue(SDValue Old, SDValue New) {
+    LLVM_DEBUG(dbgs() << " ... replacing: "; Old->dump(&DAG);
+               dbgs() << "     with:      "; New->dump(&DAG));
+
+    DAG.ReplaceAllUsesOfValueWith(Old, New);
+    if (UpdatedNodes)
+      UpdatedNodes->insert(New.getNode());
+    ReplacedNode(Old.getNode());
+  }
 };
 
 } // end anonymous namespace
@@ -2880,10 +2890,27 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     if (TLI.expandFP_TO_SINT(Node, Tmp1, DAG))
       Results.push_back(Tmp1);
     break;
+  case ISD::STRICT_FP_TO_SINT:
+    if (TLI.expandFP_TO_SINT(Node, Tmp1, DAG)) {
+      ReplaceNode(Node, Tmp1.getNode());
+      LLVM_DEBUG(dbgs() << "Successfully expanded STRICT_FP_TO_SINT node\n");
+      return true;
+    }
+    break;
   case ISD::FP_TO_UINT:
-    if (TLI.expandFP_TO_UINT(Node, Tmp1, DAG))
+    if (TLI.expandFP_TO_UINT(Node, Tmp1, Tmp2, DAG))
       Results.push_back(Tmp1);
     break;
+  case ISD::STRICT_FP_TO_UINT:
+    if (TLI.expandFP_TO_UINT(Node, Tmp1, Tmp2, DAG)) {
+      // Relink the chain.
+      DAG.ReplaceAllUsesOfValueWith(SDValue(Node,1), Tmp2);
+      // Replace the new UINT result.
+      ReplaceNodeWithValue(SDValue(Node, 0), Tmp1);
+      LLVM_DEBUG(dbgs() << "Successfully expanded STRICT_FP_TO_UINT node\n");
+      return true;
+    }
+    break;
   case ISD::LROUND:
     Results.push_back(ExpandArgFPLibCall(Node, RTLIB::LROUND_F32,
                                          RTLIB::LROUND_F64, RTLIB::LROUND_F80,

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

@@ -112,6 +112,8 @@ void DAGTypeLegalizer::PromoteIntegerResult(SDNode *N, unsigned ResNo) {
   case ISD::ZERO_EXTEND:
   case ISD::ANY_EXTEND:  Res = PromoteIntRes_INT_EXTEND(N); break;
 
+  case ISD::STRICT_FP_TO_SINT:
+  case ISD::STRICT_FP_TO_UINT:
   case ISD::FP_TO_SINT:
   case ISD::FP_TO_UINT:  Res = PromoteIntRes_FP_TO_XINT(N); break;
 
@@ -494,7 +496,20 @@ SDValue DAGTypeLegalizer::PromoteIntRes_FP_TO_XINT(SDNode *N) {
       TLI.isOperationLegalOrCustom(ISD::FP_TO_SINT, NVT))
     NewOpc = ISD::FP_TO_SINT;
 
-  SDValue Res = DAG.getNode(NewOpc, dl, NVT, N->getOperand(0));
+  if (N->getOpcode() == ISD::STRICT_FP_TO_UINT &&
+      !TLI.isOperationLegal(ISD::STRICT_FP_TO_UINT, NVT) &&
+      TLI.isOperationLegalOrCustom(ISD::STRICT_FP_TO_SINT, NVT))
+    NewOpc = ISD::STRICT_FP_TO_SINT;
+
+  SDValue Res;
+  if (N->isStrictFPOpcode()) {
+    Res = DAG.getNode(NewOpc, dl, { NVT, MVT::Other }, 
+                      { N->getOperand(0), N->getOperand(1) });
+    // Legalize the chain result - switch anything that used the old chain to
+    // use the new one.
+    ReplaceValueWith(SDValue(N, 1), Res.getValue(1));
+  } else
+    Res = DAG.getNode(NewOpc, dl, NVT, N->getOperand(0));
 
   // Assert that the converted value fits in the original type.  If it doesn't
   // (eg: because the value being converted is too big), then the result of the
@@ -503,7 +518,8 @@ SDValue DAGTypeLegalizer::PromoteIntRes_FP_TO_XINT(SDNode *N) {
   // NOTE: fp-to-uint to fp-to-sint promotion guarantees zero extend. For example:
   //   before legalization: fp-to-uint16, 65534. -> 0xfffe
   //   after legalization: fp-to-sint32, 65534. -> 0x0000fffe
-  return DAG.getNode(N->getOpcode() == ISD::FP_TO_UINT ?
+  return DAG.getNode((N->getOpcode() == ISD::FP_TO_UINT ||
+                      N->getOpcode() == ISD::STRICT_FP_TO_UINT) ?
                      ISD::AssertZext : ISD::AssertSext, dl, NVT, Res,
                      DAG.getValueType(N->getValueType(0).getScalarType()));
 }

llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h

@@ -715,6 +715,7 @@ class LLVM_LIBRARY_VISIBILITY DAGTypeLegalizer {
   bool ScalarizeVectorOperand(SDNode *N, unsigned OpNo);
   SDValue ScalarizeVecOp_BITCAST(SDNode *N);
   SDValue ScalarizeVecOp_UnaryOp(SDNode *N);
+  SDValue ScalarizeVecOp_UnaryOp_StrictFP(SDNode *N);
   SDValue ScalarizeVecOp_CONCAT_VECTORS(SDNode *N);
   SDValue ScalarizeVecOp_EXTRACT_VECTOR_ELT(SDNode *N);
   SDValue ScalarizeVecOp_VSELECT(SDNode *N);

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

@@ -333,6 +333,8 @@ SDValue VectorLegalizer::LegalizeOp(SDValue Op) {
   case ISD::STRICT_FFLOOR:
   case ISD::STRICT_FROUND:
   case ISD::STRICT_FTRUNC:
+  case ISD::STRICT_FP_TO_SINT:
+  case ISD::STRICT_FP_TO_UINT:
   case ISD::STRICT_FP_ROUND:
   case ISD::STRICT_FP_EXTEND:
     Action = TLI.getOperationAction(Node->getOpcode(), Node->getValueType(0));
@@ -862,6 +864,8 @@ SDValue VectorLegalizer::Expand(SDValue Op) {
   case ISD::STRICT_FFLOOR:
   case ISD::STRICT_FROUND:
   case ISD::STRICT_FTRUNC:
+  case ISD::STRICT_FP_TO_SINT:
+  case ISD::STRICT_FP_TO_UINT:
     return ExpandStrictFPOp(Op);
   case ISD::VECREDUCE_ADD:
   case ISD::VECREDUCE_MUL:
@@ -1186,9 +1190,13 @@ SDValue VectorLegalizer::ExpandABS(SDValue Op) {
 
 SDValue VectorLegalizer::ExpandFP_TO_UINT(SDValue Op) {
   // Attempt to expand using TargetLowering.
-  SDValue Result;
-  if (TLI.expandFP_TO_UINT(Op.getNode(), Result, DAG))
+  SDValue Result, Chain;
+  if (TLI.expandFP_TO_UINT(Op.getNode(), Result, Chain, DAG)) {
+    if (Op.getNode()->isStrictFPOpcode())
+      // Relink the chain
+      DAG.ReplaceAllUsesOfValueWith(Op.getValue(1), Chain);
     return Result;
+  }
 
   // Otherwise go ahead and unroll.
   return DAG.UnrollVectorOp(Op.getNode());

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp

@@ -171,6 +171,8 @@ void DAGTypeLegalizer::ScalarizeVectorResult(SDNode *N, unsigned ResNo) {
   case ISD::STRICT_FFLOOR:
   case ISD::STRICT_FROUND:
   case ISD::STRICT_FTRUNC:
+  case ISD::STRICT_FP_TO_SINT:
+  case ISD::STRICT_FP_TO_UINT:
   case ISD::STRICT_FP_EXTEND:
     R = ScalarizeVecRes_StrictFPOp(N);
     break;
@@ -604,6 +606,10 @@ bool DAGTypeLegalizer::ScalarizeVectorOperand(SDNode *N, unsigned OpNo) {
     case ISD::UINT_TO_FP:
       Res = ScalarizeVecOp_UnaryOp(N);
       break;
+    case ISD::STRICT_FP_TO_SINT:
+    case ISD::STRICT_FP_TO_UINT:
+      Res = ScalarizeVecOp_UnaryOp_StrictFP(N);
+      break;
     case ISD::CONCAT_VECTORS:
       Res = ScalarizeVecOp_CONCAT_VECTORS(N);
       break;
@@ -679,6 +685,23 @@ SDValue DAGTypeLegalizer::ScalarizeVecOp_UnaryOp(SDNode *N) {
   return DAG.getNode(ISD::SCALAR_TO_VECTOR, SDLoc(N), N->getValueType(0), Op);
 }
 
+/// If the input is a vector that needs to be scalarized, it must be <1 x ty>.
+/// Do the strict FP operation on the element instead.
+SDValue DAGTypeLegalizer::ScalarizeVecOp_UnaryOp_StrictFP(SDNode *N) {
+  assert(N->getValueType(0).getVectorNumElements() == 1 &&
+         "Unexpected vector type!");
+  SDValue Elt = GetScalarizedVector(N->getOperand(1));
+  SDValue Res = DAG.getNode(N->getOpcode(), SDLoc(N),
+                            { N->getValueType(0).getScalarType(), MVT::Other },
+                            { N->getOperand(0), Elt });
+  // Legalize the chain result - switch anything that used the old chain to
+  // use the new one.
+  ReplaceValueWith(SDValue(N, 1), Res.getValue(1));
+  // Revectorize the result so the types line up with what the uses of this
+  // expression expect.
+  return DAG.getNode(ISD::SCALAR_TO_VECTOR, SDLoc(N), N->getValueType(0), Res);
+}
+
 /// The vectors to concatenate have length one - use a BUILD_VECTOR instead.
 SDValue DAGTypeLegalizer::ScalarizeVecOp_CONCAT_VECTORS(SDNode *N) {
   SmallVector<SDValue, 8> Ops(N->getNumOperands());
@@ -883,7 +906,9 @@ void DAGTypeLegalizer::SplitVectorResult(SDNode *N, unsigned ResNo) {
   case ISD::FP_ROUND:
   case ISD::STRICT_FP_ROUND:
   case ISD::FP_TO_SINT:
+  case ISD::STRICT_FP_TO_SINT:
   case ISD::FP_TO_UINT:
+  case ISD::STRICT_FP_TO_UINT:
   case ISD::FRINT:
   case ISD::FROUND:
   case ISD::FSIN:
@@ -1987,6 +2012,8 @@ bool DAGTypeLegalizer::SplitVectorOperand(SDNode *N, unsigned OpNo) {
       break;
     case ISD::FP_TO_SINT:
     case ISD::FP_TO_UINT:
+    case ISD::STRICT_FP_TO_SINT:
+    case ISD::STRICT_FP_TO_UINT:
     case ISD::CTTZ:
     case ISD::CTLZ:
     case ISD::CTPOP:
@@ -2814,6 +2841,8 @@ void DAGTypeLegalizer::WidenVectorResult(SDNode *N, unsigned ResNo) {
 
   case ISD::STRICT_FP_EXTEND:
   case ISD::STRICT_FP_ROUND:
+  case ISD::STRICT_FP_TO_SINT:
+  case ISD::STRICT_FP_TO_UINT:
     Res = WidenVecRes_Convert_StrictFP(N);
     break;
 
@@ -4129,7 +4158,9 @@ bool DAGTypeLegalizer::WidenVectorOperand(SDNode *N, unsigned OpNo) {
   case ISD::FP_EXTEND:
   case ISD::STRICT_FP_EXTEND:
   case ISD::FP_TO_SINT:
+  case ISD::STRICT_FP_TO_SINT:
   case ISD::FP_TO_UINT:
+  case ISD::STRICT_FP_TO_UINT:
   case ISD::SINT_TO_FP:
   case ISD::UINT_TO_FP:
   case ISD::TRUNCATE:

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -7778,6 +7778,8 @@ SDNode* SelectionDAG::mutateStrictFPToFP(SDNode *Node) {
   case ISD::STRICT_FTRUNC:     NewOpc = ISD::FTRUNC;     break;
   case ISD::STRICT_FP_ROUND:   NewOpc = ISD::FP_ROUND;   break;
   case ISD::STRICT_FP_EXTEND:  NewOpc = ISD::FP_EXTEND;  break;
+  case ISD::STRICT_FP_TO_SINT: NewOpc = ISD::FP_TO_SINT; break;
+  case ISD::STRICT_FP_TO_UINT: NewOpc = ISD::FP_TO_UINT; break;
   }
 
   assert(Node->getNumValues() == 2 && "Unexpected number of results!");

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -6106,6 +6106,8 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
   case Intrinsic::experimental_constrained_fdiv:
   case Intrinsic::experimental_constrained_frem:
   case Intrinsic::experimental_constrained_fma:
+  case Intrinsic::experimental_constrained_fptosi:
+  case Intrinsic::experimental_constrained_fptoui:
   case Intrinsic::experimental_constrained_fptrunc:
   case Intrinsic::experimental_constrained_fpext:
   case Intrinsic::experimental_constrained_sqrt:
@@ -6899,6 +6901,12 @@ void SelectionDAGBuilder::visitConstrainedFPIntrinsic(
   case Intrinsic::experimental_constrained_fma:
     Opcode = ISD::STRICT_FMA;
     break;
+  case Intrinsic::experimental_constrained_fptosi:
+    Opcode = ISD::STRICT_FP_TO_SINT;
+    break;
+  case Intrinsic::experimental_constrained_fptoui:
+    Opcode = ISD::STRICT_FP_TO_UINT;
+    break;
   case Intrinsic::experimental_constrained_fptrunc:
     Opcode = ISD::STRICT_FP_ROUND;
     break;

llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp

@@ -325,7 +325,9 @@ std::string SDNode::getOperationName(const SelectionDAG *G) const {
   case ISD::SINT_TO_FP:                 return "sint_to_fp";
   case ISD::UINT_TO_FP:                 return "uint_to_fp";
   case ISD::FP_TO_SINT:                 return "fp_to_sint";
+  case ISD::STRICT_FP_TO_SINT:          return "strict_fp_to_sint";
   case ISD::FP_TO_UINT:                 return "fp_to_uint";
+  case ISD::STRICT_FP_TO_UINT:          return "strict_fp_to_uint";
   case ISD::BITCAST:                    return "bitcast";
   case ISD::ADDRSPACECAST:              return "addrspacecast";
   case ISD::FP16_TO_FP:                 return "fp16_to_fp";