[llvm] [TableGen] Improvements to Named operands in InstrInfoEmitter (PR #124960)

[Craig Topper via llvm-commits]

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@@ -283,22 +241,52 @@ void InstrInfoEmitter::emitOperandNameMappings(
     raw_ostream &OS, const CodeGenTarget &Target,
     ArrayRef<const CodeGenInstruction *> NumberedInstructions) {
   StringRef Namespace = Target.getInstNamespace();
-  // Map of operand names to their enumeration value.  This will be used to
-  // generate the OpName enum.
-  std::map<std::string, unsigned> Operands;
-  OpNameMapTy OperandMap;
 
-  initOperandMapData(NumberedInstructions, Namespace, Operands, OperandMap);
+  /// To facilitate assigning OpName enum values in the sorted alphabetical
+  /// order, we go through an indirection from OpName -> ID, and Enum -> ID.
+  /// This allows us to build the OpList and assign IDs to OpNames in a single
+  /// scan of the instructions below.
+
+  // Map of operand names to their ID.
+  std::map<std::string, unsigned> OperandNameToID;
+  // Map from operand name enum value -> ID.
+  std::vector<unsigned> OperandEnumToID;
+
+  /// The keys of this map is a map which have OpName ID values as their keys
+  /// and instruction operand indices as their values. The values of this map
+  /// are lists of instruction names. This map helps to unique entries among
+  /// instructions that have identical OpName -> Operand index mapping.
+  std::map<std::map<unsigned, unsigned>, std::vector<std::string>> OperandMap;
+
+  // Max operand index seen.
+  unsigned MaxOperandNo = 0;
+  unsigned NumOperandNames = 0;
+
+  for (const CodeGenInstruction *Inst : NumberedInstructions) {
+    if (!Inst->TheDef->getValueAsBit("UseNamedOperandTable"))
+      continue;
+    std::map<unsigned, unsigned> OpList;
+    for (const auto &Info : Inst->Operands) {
+      auto [I, Inserted] = OperandNameToID.try_emplace(Info.Name, 0);
+      if (Inserted)
+        I->second = NumOperandNames++;
+      OpList[I->second] = Info.MIOperandNo;
+      MaxOperandNo = std::max(MaxOperandNo, Info.MIOperandNo);
+    }
+    OperandMap[OpList].push_back(Inst->TheDef->getName().str());
+  }
+
+  OperandEnumToID.reserve(NumOperandNames);
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topperc wrote:

Could we change `OperandNameToID` to a `MapVector<std::string, unsigned>`? Iterating over that will be the order they were inserted. Then I don't think you would need OperandEnumToID.

https://github.com/llvm/llvm-project/pull/124960