[TargetLowering] Simplify the interface for expandCTPOP/expandCTLZ/expandCTTZ.

There is no need to return a bool and have an SDValue output
parameter. Just return the SDValue and let the caller check if it
is null.

I have another patch to add more callers of these so I thought
I'd clean up the interface first.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D112267

Author: topperc

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -4446,23 +4446,20 @@ class TargetLowering : public TargetLoweringBase {
   /// Expand CTPOP nodes. Expands vector/scalar CTPOP nodes,
   /// vector nodes can only succeed if all operations are legal/custom.
   /// \param N Node to expand
-  /// \param Result output after conversion
-  /// \returns True, if the expansion was successful, false otherwise
-  bool expandCTPOP(SDNode *N, SDValue &Result, SelectionDAG &DAG) const;
+  /// \returns The expansion result or SDValue() if it fails.
+  SDValue expandCTPOP(SDNode *N, SelectionDAG &DAG) const;
 
   /// Expand CTLZ/CTLZ_ZERO_UNDEF nodes. Expands vector/scalar CTLZ nodes,
   /// vector nodes can only succeed if all operations are legal/custom.
   /// \param N Node to expand
-  /// \param Result output after conversion
-  /// \returns True, if the expansion was successful, false otherwise
-  bool expandCTLZ(SDNode *N, SDValue &Result, SelectionDAG &DAG) const;
+  /// \returns The expansion result or SDValue() if it fails.
+  SDValue expandCTLZ(SDNode *N, SelectionDAG &DAG) const;
 
   /// Expand CTTZ/CTTZ_ZERO_UNDEF nodes. Expands vector/scalar CTTZ nodes,
   /// vector nodes can only succeed if all operations are legal/custom.
   /// \param N Node to expand
-  /// \param Result output after conversion
-  /// \returns True, if the expansion was successful, false otherwise
-  bool expandCTTZ(SDNode *N, SDValue &Result, SelectionDAG &DAG) const;
+  /// \returns The expansion result or SDValue() if it fails.
+  SDValue expandCTTZ(SDNode *N, SelectionDAG &DAG) const;
 
   /// Expand ABS nodes. Expands vector/scalar ABS nodes,
   /// vector nodes can only succeed if all operations are legal/custom.

llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -2688,17 +2688,17 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
       Results.push_back(Tmp1);
     break;
   case ISD::CTPOP:
-    if (TLI.expandCTPOP(Node, Tmp1, DAG))
+    if ((Tmp1 = TLI.expandCTPOP(Node, DAG)))
       Results.push_back(Tmp1);
     break;
   case ISD::CTLZ:
   case ISD::CTLZ_ZERO_UNDEF:
-    if (TLI.expandCTLZ(Node, Tmp1, DAG))
+    if ((Tmp1 = TLI.expandCTLZ(Node, DAG)))
       Results.push_back(Tmp1);
     break;
   case ISD::CTTZ:
   case ISD::CTTZ_ZERO_UNDEF:
-    if (TLI.expandCTTZ(Node, Tmp1, DAG))
+    if ((Tmp1 = TLI.expandCTTZ(Node, DAG)))
       Results.push_back(Tmp1);
     break;
   case ISD::BITREVERSE:

llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp

@@ -783,22 +783,22 @@ void VectorLegalizer::Expand(SDNode *Node, SmallVectorImpl<SDValue> &Results) {
     ExpandBITREVERSE(Node, Results);
     return;
   case ISD::CTPOP:
-    if (TLI.expandCTPOP(Node, Tmp, DAG)) {
-      Results.push_back(Tmp);
+    if (SDValue Expanded = TLI.expandCTPOP(Node, DAG)) {
+      Results.push_back(Expanded);
       return;
     }
     break;
   case ISD::CTLZ:
   case ISD::CTLZ_ZERO_UNDEF:
-    if (TLI.expandCTLZ(Node, Tmp, DAG)) {
-      Results.push_back(Tmp);
+    if (SDValue Expanded = TLI.expandCTLZ(Node, DAG)) {
+      Results.push_back(Expanded);
       return;
     }
     break;
   case ISD::CTTZ:
   case ISD::CTTZ_ZERO_UNDEF:
-    if (TLI.expandCTTZ(Node, Tmp, DAG)) {
-      Results.push_back(Tmp);
+    if (SDValue Expanded = TLI.expandCTTZ(Node, DAG)) {
+      Results.push_back(Expanded);
       return;
     }
     break;

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -6991,8 +6991,7 @@ static bool canExpandVectorCTPOP(const TargetLowering &TLI, EVT VT) {
          TLI.isOperationLegalOrCustomOrPromote(ISD::AND, VT);
 }
 
-bool TargetLowering::expandCTPOP(SDNode *Node, SDValue &Result,
-                                 SelectionDAG &DAG) const {
+SDValue TargetLowering::expandCTPOP(SDNode *Node, SelectionDAG &DAG) const {
   SDLoc dl(Node);
   EVT VT = Node->getValueType(0);
   EVT ShVT = getShiftAmountTy(VT, DAG.getDataLayout());
@@ -7002,11 +7001,11 @@ bool TargetLowering::expandCTPOP(SDNode *Node, SDValue &Result,
 
   // TODO: Add support for irregular type lengths.
   if (!(Len <= 128 && Len % 8 == 0))
-    return false;
+    return SDValue();
 
   // Only expand vector types if we have the appropriate vector bit operations.
   if (VT.isVector() && !canExpandVectorCTPOP(*this, VT))
-    return false;
+    return SDValue();
 
   // This is the "best" algorithm from
   // http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
@@ -7043,12 +7042,10 @@ bool TargetLowering::expandCTPOP(SDNode *Node, SDValue &Result,
         DAG.getNode(ISD::SRL, dl, VT, DAG.getNode(ISD::MUL, dl, VT, Op, Mask01),
                     DAG.getConstant(Len - 8, dl, ShVT));
 
-  Result = Op;
-  return true;
+  return Op;
 }
 
-bool TargetLowering::expandCTLZ(SDNode *Node, SDValue &Result,
-                                SelectionDAG &DAG) const {
+SDValue TargetLowering::expandCTLZ(SDNode *Node, SelectionDAG &DAG) const {
   SDLoc dl(Node);
   EVT VT = Node->getValueType(0);
   EVT ShVT = getShiftAmountTy(VT, DAG.getDataLayout());
@@ -7057,10 +7054,8 @@ bool TargetLowering::expandCTLZ(SDNode *Node, SDValue &Result,
 
   // If the non-ZERO_UNDEF version is supported we can use that instead.
   if (Node->getOpcode() == ISD::CTLZ_ZERO_UNDEF &&
-      isOperationLegalOrCustom(ISD::CTLZ, VT)) {
-    Result = DAG.getNode(ISD::CTLZ, dl, VT, Op);
-    return true;
-  }
+      isOperationLegalOrCustom(ISD::CTLZ, VT))
+    return DAG.getNode(ISD::CTLZ, dl, VT, Op);
 
   // If the ZERO_UNDEF version is supported use that and handle the zero case.
   if (isOperationLegalOrCustom(ISD::CTLZ_ZERO_UNDEF, VT)) {
@@ -7069,9 +7064,8 @@ bool TargetLowering::expandCTLZ(SDNode *Node, SDValue &Result,
     SDValue CTLZ = DAG.getNode(ISD::CTLZ_ZERO_UNDEF, dl, VT, Op);
     SDValue Zero = DAG.getConstant(0, dl, VT);
     SDValue SrcIsZero = DAG.getSetCC(dl, SetCCVT, Op, Zero, ISD::SETEQ);
-    Result = DAG.getNode(ISD::SELECT, dl, VT, SrcIsZero,
-                         DAG.getConstant(NumBitsPerElt, dl, VT), CTLZ);
-    return true;
+    return DAG.getNode(ISD::SELECT, dl, VT, SrcIsZero,
+                       DAG.getConstant(NumBitsPerElt, dl, VT), CTLZ);
   }
 
   // Only expand vector types if we have the appropriate vector bit operations.
@@ -7081,7 +7075,7 @@ bool TargetLowering::expandCTLZ(SDNode *Node, SDValue &Result,
                          !canExpandVectorCTPOP(*this, VT)) ||
                         !isOperationLegalOrCustom(ISD::SRL, VT) ||
                         !isOperationLegalOrCustomOrPromote(ISD::OR, VT)))
-    return false;
+    return SDValue();
 
   // for now, we do this:
   // x = x | (x >> 1);
@@ -7098,23 +7092,19 @@ bool TargetLowering::expandCTLZ(SDNode *Node, SDValue &Result,
                      DAG.getNode(ISD::SRL, dl, VT, Op, Tmp));
   }
   Op = DAG.getNOT(dl, Op, VT);
-  Result = DAG.getNode(ISD::CTPOP, dl, VT, Op);
-  return true;
+  return DAG.getNode(ISD::CTPOP, dl, VT, Op);
 }
 
-bool TargetLowering::expandCTTZ(SDNode *Node, SDValue &Result,
-                                SelectionDAG &DAG) const {
+SDValue TargetLowering::expandCTTZ(SDNode *Node, SelectionDAG &DAG) const {
   SDLoc dl(Node);
   EVT VT = Node->getValueType(0);
   SDValue Op = Node->getOperand(0);
   unsigned NumBitsPerElt = VT.getScalarSizeInBits();
 
   // If the non-ZERO_UNDEF version is supported we can use that instead.
   if (Node->getOpcode() == ISD::CTTZ_ZERO_UNDEF &&
-      isOperationLegalOrCustom(ISD::CTTZ, VT)) {
-    Result = DAG.getNode(ISD::CTTZ, dl, VT, Op);
-    return true;
-  }
+      isOperationLegalOrCustom(ISD::CTTZ, VT))
+    return DAG.getNode(ISD::CTTZ, dl, VT, Op);
 
   // If the ZERO_UNDEF version is supported use that and handle the zero case.
   if (isOperationLegalOrCustom(ISD::CTTZ_ZERO_UNDEF, VT)) {
@@ -7123,9 +7113,8 @@ bool TargetLowering::expandCTTZ(SDNode *Node, SDValue &Result,
     SDValue CTTZ = DAG.getNode(ISD::CTTZ_ZERO_UNDEF, dl, VT, Op);
     SDValue Zero = DAG.getConstant(0, dl, VT);
     SDValue SrcIsZero = DAG.getSetCC(dl, SetCCVT, Op, Zero, ISD::SETEQ);
-    Result = DAG.getNode(ISD::SELECT, dl, VT, SrcIsZero,
-                         DAG.getConstant(NumBitsPerElt, dl, VT), CTTZ);
-    return true;
+    return DAG.getNode(ISD::SELECT, dl, VT, SrcIsZero,
+                       DAG.getConstant(NumBitsPerElt, dl, VT), CTTZ);
   }
 
   // Only expand vector types if we have the appropriate vector bit operations.
@@ -7137,7 +7126,7 @@ bool TargetLowering::expandCTTZ(SDNode *Node, SDValue &Result,
                         !isOperationLegalOrCustom(ISD::SUB, VT) ||
                         !isOperationLegalOrCustomOrPromote(ISD::AND, VT) ||
                         !isOperationLegalOrCustomOrPromote(ISD::XOR, VT)))
-    return false;
+    return SDValue();
 
   // for now, we use: { return popcount(~x & (x - 1)); }
   // unless the target has ctlz but not ctpop, in which case we use:
@@ -7149,14 +7138,11 @@ bool TargetLowering::expandCTTZ(SDNode *Node, SDValue &Result,
 
   // If ISD::CTLZ is legal and CTPOP isn't, then do that instead.
   if (isOperationLegal(ISD::CTLZ, VT) && !isOperationLegal(ISD::CTPOP, VT)) {
-    Result =
-        DAG.getNode(ISD::SUB, dl, VT, DAG.getConstant(NumBitsPerElt, dl, VT),
-                    DAG.getNode(ISD::CTLZ, dl, VT, Tmp));
-    return true;
+    return DAG.getNode(ISD::SUB, dl, VT, DAG.getConstant(NumBitsPerElt, dl, VT),
+                       DAG.getNode(ISD::CTLZ, dl, VT, Tmp));
   }
 
-  Result = DAG.getNode(ISD::CTPOP, dl, VT, Tmp);
-  return true;
+  return DAG.getNode(ISD::CTPOP, dl, VT, Tmp);
 }
 
 bool TargetLowering::expandABS(SDNode *N, SDValue &Result,