[LLVM][TableGen] Minor cleanup in CodeGenInstruction

- Use StringRef instead of std::string for `AsmString`.
- Change `hadOperandNamed` to return index as std::optional and
  rename it to `findOperandNamed`.
- Change `SubOperandAlias` to return std::optional and rename it
  to `findSubOperandAlias`.

Author: jurahul

llvm/utils/TableGen/AsmMatcherEmitter.cpp

@@ -1712,11 +1712,11 @@ void AsmMatcherInfo::buildInstructionOperandReference(MatchableInfo *II,
   MatchableInfo::AsmOperand *Op = &II->AsmOperands[AsmOpIdx];
 
   // Map this token to an operand.
-  unsigned Idx;
-  if (!Operands.hasOperandNamed(OperandName, Idx))
+  std::optional<unsigned> MayBeIdx = Operands.findOperandNamed(OperandName);
+  if (!MayBeIdx)
     PrintFatalError(II->TheDef->getLoc(),
                     "error: unable to find operand: '" + OperandName + "'");
-
+  unsigned Idx = *MayBeIdx;
   // If the instruction operand has multiple suboperands, but the parser
   // match class for the asm operand is still the default "ImmAsmOperand",
   // then handle each suboperand separately.

llvm/utils/TableGen/CodeEmitterGen.cpp

@@ -123,12 +123,11 @@ bool CodeEmitterGen::addCodeToMergeInOperand(const Record *R,
   // operand number. Non-matching operands are assumed to be in
   // order.
   unsigned OpIdx;
-  std::pair<unsigned, unsigned> SubOp;
-  if (CGI.Operands.hasSubOperandAlias(VarName, SubOp)) {
-    OpIdx = CGI.Operands[SubOp.first].MIOperandNo + SubOp.second;
-  } else if (CGI.Operands.hasOperandNamed(VarName, OpIdx)) {
+  if (auto SubOp = CGI.Operands.findSubOperandAlias(VarName)) {
+    OpIdx = CGI.Operands[SubOp->first].MIOperandNo + SubOp->second;
+  } else if (auto MayBeOpIdx = CGI.Operands.findOperandNamed(VarName)) {
     // Get the machine operand number for the indicated operand.
-    OpIdx = CGI.Operands[OpIdx].MIOperandNo;
+    OpIdx = CGI.Operands[*MayBeOpIdx].MIOperandNo;
   } else {
     PrintError(R, Twine("No operand named ") + VarName + " in record " +
                       R->getName());

llvm/utils/TableGen/Common/CodeGenInstruction.cpp

@@ -183,8 +183,8 @@ CGIOperandList::CGIOperandList(const Record *R) : TheDef(R) {
       // If we have no explicit sub-op dag, but have an top-level encoder
       // method, the single encoder will multiple sub-ops, itself.
       OpInfo.EncoderMethodNames[0] = EncoderMethod;
-      for (unsigned j = 1; j < NumOps; ++j)
-        OpInfo.DoNotEncode[j] = true;
+      OpInfo.DoNotEncode.set();
+      OpInfo.DoNotEncode[0] = false;
     }
 
     MIOperandNo += NumOps;
@@ -199,36 +199,31 @@ CGIOperandList::CGIOperandList(const Record *R) : TheDef(R) {
 /// specified name, abort.
 ///
 unsigned CGIOperandList::getOperandNamed(StringRef Name) const {
-  unsigned OpIdx;
-  if (hasOperandNamed(Name, OpIdx))
-    return OpIdx;
+  std::optional<unsigned> OpIdx = findOperandNamed(Name);
+  if (OpIdx)
+    return *OpIdx;
   PrintFatalError(TheDef->getLoc(), "'" + TheDef->getName() +
                                         "' does not have an operand named '$" +
                                         Name + "'!");
 }
 
-/// hasOperandNamed - Query whether the instruction has an operand of the
-/// given name. If so, return true and set OpIdx to the index of the
-/// operand. Otherwise, return false.
-bool CGIOperandList::hasOperandNamed(StringRef Name, unsigned &OpIdx) const {
+/// findOperandNamed - Query whether the instruction has an operand of the
+/// given name. If so, the index of the operand. Otherwise, return std::nullopt.
+std::optional<unsigned> CGIOperandList::findOperandNamed(StringRef Name) const {
   assert(!Name.empty() && "Cannot search for operand with no name!");
-  for (unsigned i = 0, e = OperandList.size(); i != e; ++i)
-    if (OperandList[i].Name == Name) {
-      OpIdx = i;
-      return true;
-    }
-  return false;
+  for (const auto &[Index, Opnd] : enumerate(OperandList))
+    if (Opnd.Name == Name)
+      return Index;
+  return std::nullopt;
 }
 
-bool CGIOperandList::hasSubOperandAlias(
-    StringRef Name, std::pair<unsigned, unsigned> &SubOp) const {
+std::optional<std::pair<unsigned, unsigned>>
+CGIOperandList::findSubOperandAlias(StringRef Name) const {
   assert(!Name.empty() && "Cannot search for operand with no name!");
   auto SubOpIter = SubOpAliases.find(Name);
-  if (SubOpIter != SubOpAliases.end()) {
-    SubOp = SubOpIter->second;
-    return true;
-  }
-  return false;
+  if (SubOpIter != SubOpAliases.end())
+    return SubOpIter->second;
+  return std::nullopt;
 }
 
 std::pair<unsigned, unsigned>
@@ -251,9 +246,7 @@ CGIOperandList::ParseOperandName(StringRef Op, bool AllowWholeOp) {
     OpName = OpName.substr(0, DotIdx);
   }
 
-  unsigned OpIdx;
-
-  if (std::pair<unsigned, unsigned> SubOp; hasSubOperandAlias(OpName, SubOp)) {
+  if (auto SubOp = findSubOperandAlias(OpName)) {
     // Found a name for a piece of an operand, just return it directly.
     if (!SubOpName.empty()) {
       PrintFatalError(
@@ -262,10 +255,10 @@ CGIOperandList::ParseOperandName(StringRef Op, bool AllowWholeOp) {
               ": Cannot use dotted suboperand name within suboperand '" +
               OpName + "'");
     }
-    return SubOp;
+    return *SubOp;
   }
 
-  OpIdx = getOperandNamed(OpName);
+  unsigned OpIdx = getOperandNamed(OpName);
 
   if (SubOpName.empty()) { // If no suboperand name was specified:
     // If one was needed, throw.

llvm/utils/TableGen/Common/CodeGenInstruction.h

@@ -127,10 +127,9 @@ class CGIOperandList {
     /// getTiedOperand - If this operand is tied to another one, return the
     /// other operand number.  Otherwise, return -1.
     int getTiedRegister() const {
-      for (const CGIOperandList::ConstraintInfo &CI : Constraints) {
+      for (const CGIOperandList::ConstraintInfo &CI : Constraints)
         if (CI.isTied())
           return CI.getTiedOperand();
-      }
       return -1;
     }
   };
@@ -176,13 +175,13 @@ class CGIOperandList {
   /// specified name, abort.
   unsigned getOperandNamed(StringRef Name) const;
 
-  /// hasOperandNamed - Query whether the instruction has an operand of the
-  /// given name. If so, return true and set OpIdx to the index of the
-  /// operand. Otherwise, return false.
-  bool hasOperandNamed(StringRef Name, unsigned &OpIdx) const;
+  /// findOperandNamed - Query whether the instruction has an operand of the
+  /// given name. If so, the index of the operand. Otherwise, return
+  /// std::nullopt.
+  std::optional<unsigned> findOperandNamed(StringRef Name) const;
 
-  bool hasSubOperandAlias(StringRef Name,
-                          std::pair<unsigned, unsigned> &SubOp) const;
+  std::optional<std::pair<unsigned, unsigned>>
+  findSubOperandAlias(StringRef Name) const;
 
   /// ParseOperandName - Parse an operand name like "$foo" or "$foo.bar",
   /// where $foo is a whole operand and $foo.bar refers to a suboperand.