[SelectionDAG] Expand UADDO/USUBO into ADD/SUBCARRY if legal for target

Additionally, implement handling of ADD/SUBCARRY on Hexagon, utilizing
the UADDO/USUBO expansion.

Differential Revision: https://reviews.llvm.org/D47559

llvm-svn: 333751

4 files changed, 48 insertions, 5 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.cpp b/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.cpp
index 0d0b35118c1..efb4c2eb0fc 100644
--- a/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.cpp
@@ -762,6 +762,15 @@ void HexagonDAGToDAGISel::SelectFrameIndex(SDNode *N) {
   ReplaceNode(N, R);
 }
 
+void HexagonDAGToDAGISel::SelectAddSubCarry(SDNode *N) {
+  unsigned OpcCarry = N->getOpcode() == HexagonISD::ADDC ? Hexagon::A4_addp_c
+                                                         : Hexagon::A4_subp_c;
+  SDNode *C = CurDAG->getMachineNode(OpcCarry, SDLoc(N), N->getVTList(),
+                                     { N->getOperand(0), N->getOperand(1),
+                                       N->getOperand(2) });
+  ReplaceNode(N, C);
+}
+
 void HexagonDAGToDAGISel::SelectVAlign(SDNode *N) {
   MVT ResTy = N->getValueType(0).getSimpleVT();
   if (HST->isHVXVectorType(ResTy, true))
@@ -875,6 +884,9 @@ void HexagonDAGToDAGISel::Select(SDNode *N) {
   case ISD::STORE:                return SelectStore(N);
   case ISD::INTRINSIC_W_CHAIN:    return SelectIntrinsicWChain(N);
   case ISD::INTRINSIC_WO_CHAIN:   return SelectIntrinsicWOChain(N);
+
+  case HexagonISD::ADDC:
+  case HexagonISD::SUBC:          return SelectAddSubCarry(N);
   case HexagonISD::VALIGN:        return SelectVAlign(N);
   case HexagonISD::VALIGNADDR:    return SelectVAlignAddr(N);
   case HexagonISD::TYPECAST:      return SelectTypecast(N);
diff --git a/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.h b/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.h
index 1c3379bf015..f4f09dd4e75 100644
--- a/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.h
+++ b/llvm/lib/Target/Hexagon/HexagonISelDAGToDAG.h
@@ -105,6 +105,7 @@ public:
   void SelectV65Gather(SDNode *N);
   void SelectV65GatherPred(SDNode *N);
   void SelectHVXDualOutput(SDNode *N);
+  void SelectAddSubCarry(SDNode *N);
   void SelectVAlign(SDNode *N);
   void SelectVAlignAddr(SDNode *N);
   void SelectTypecast(SDNode *N);
diff --git a/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp b/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
index 4a85427032c..a63af51bf86 100644
--- a/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonISelLowering.cpp
@@ -1327,13 +1327,18 @@ HexagonTargetLowering::HexagonTargetLowering(const TargetMachine &TM,
     setMinimumJumpTableEntries(std::numeric_limits<int>::max());
   setOperationAction(ISD::BR_JT, MVT::Other, Expand);
 
-  // Only add and sub that detect overflow are the saturating ones.
+  // Hexagon has A4_addp_c and A4_subp_c that take and generate a carry bit,
+  // but they only operate on i64.
   for (MVT VT : MVT::integer_valuetypes()) {
-    setOperationAction(ISD::UADDO, VT, Expand);
-    setOperationAction(ISD::SADDO, VT, Expand);
-    setOperationAction(ISD::USUBO, VT, Expand);
-    setOperationAction(ISD::SSUBO, VT, Expand);
+    setOperationAction(ISD::UADDO,    VT, Expand);
+    setOperationAction(ISD::USUBO,    VT, Expand);
+    setOperationAction(ISD::SADDO,    VT, Expand);
+    setOperationAction(ISD::SSUBO,    VT, Expand);
+    setOperationAction(ISD::ADDCARRY, VT, Expand);
+    setOperationAction(ISD::SUBCARRY, VT, Expand);
   }
+  setOperationAction(ISD::ADDCARRY, MVT::i64, Custom);
+  setOperationAction(ISD::SUBCARRY, MVT::i64, Custom);
 
   setOperationAction(ISD::CTLZ, MVT::i8,  Promote);
   setOperationAction(ISD::CTLZ, MVT::i16, Promote);
@@ -1681,6 +1686,8 @@ HexagonTargetLowering::HexagonTargetLowering(const TargetMachine &TM,
 
 const char* HexagonTargetLowering::getTargetNodeName(unsigned Opcode) const {
   switch ((HexagonISD::NodeType)Opcode) {
+  case HexagonISD::ADDC:          return "HexagonISD::ADDC";
+  case HexagonISD::SUBC:          return "HexagonISD::SUBC";
   case HexagonISD::ALLOCA:        return "HexagonISD::ALLOCA";
   case HexagonISD::AT_GOT:        return "HexagonISD::AT_GOT";
   case HexagonISD::AT_PCREL:      return "HexagonISD::AT_PCREL";
@@ -2706,6 +2713,24 @@ HexagonTargetLowering::LowerUnalignedLoad(SDValue Op, SelectionDAG &DAG)
 }
 
 SDValue
+HexagonTargetLowering::LowerAddSubCarry(SDValue Op, SelectionDAG &DAG) const {
+  const SDLoc &dl(Op);
+  unsigned Opc = Op.getOpcode();
+  SDValue X = Op.getOperand(0), Y = Op.getOperand(1), C = Op.getOperand(2);
+
+  if (Opc == ISD::ADDCARRY)
+    return DAG.getNode(HexagonISD::ADDC, dl, Op.getNode()->getVTList(),
+                       { X, Y, C });
+
+  EVT CarryTy = C.getValueType();
+  SDValue SubC = DAG.getNode(HexagonISD::SUBC, dl, Op.getNode()->getVTList(),
+                             { X, Y, DAG.getLogicalNOT(dl, C, CarryTy) });
+  SDValue Out[] = { SubC.getValue(0),
+                    DAG.getLogicalNOT(dl, SubC.getValue(1), CarryTy) };
+  return DAG.getMergeValues(Out, dl);
+}
+
+SDValue
 HexagonTargetLowering::LowerEH_RETURN(SDValue Op, SelectionDAG &DAG) const {
   SDValue Chain     = Op.getOperand(0);
   SDValue Offset    = Op.getOperand(1);
@@ -2763,6 +2788,8 @@ HexagonTargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const {
     case ISD::VECTOR_SHUFFLE:       return LowerVECTOR_SHUFFLE(Op, DAG);
     case ISD::BITCAST:              return LowerBITCAST(Op, DAG);
     case ISD::LOAD:                 return LowerUnalignedLoad(Op, DAG);
+    case ISD::ADDCARRY:
+    case ISD::SUBCARRY:             return LowerAddSubCarry(Op, DAG);
     case ISD::SRA:
     case ISD::SHL:
     case ISD::SRL:                  return LowerVECTOR_SHIFT(Op, DAG);
diff --git a/llvm/lib/Target/Hexagon/HexagonISelLowering.h b/llvm/lib/Target/Hexagon/HexagonISelLowering.h
index 5ed26101d58..cb570b4dc7f 100644
--- a/llvm/lib/Target/Hexagon/HexagonISelLowering.h
+++ b/llvm/lib/Target/Hexagon/HexagonISelLowering.h
@@ -36,6 +36,8 @@ namespace HexagonISD {
 
       CONST32 = OP_BEGIN,
       CONST32_GP,  // For marking data present in GP.
+      ADDC,        // Add with carry: (X, Y, Cin) -> (X+Y, Cout).
+      SUBC,        // Sub with carry: (X, Y, Cin) -> (X+~Y+Cin, Cout).
       ALLOCA,
 
       AT_GOT,      // Index in GOT.
@@ -162,6 +164,7 @@ namespace HexagonISD {
     SDValue LowerSIGN_EXTEND(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerZERO_EXTEND(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerUnalignedLoad(SDValue Op, SelectionDAG &DAG) const;
+    SDValue LowerAddSubCarry(SDValue Op, SelectionDAG &DAG) const;
 
     SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const;
     SDValue LowerINLINEASM(SDValue Op, SelectionDAG &DAG) const;