[llvm] [TableGen] Implement getOperandIdxName (PR #154944)

[Matt Arsenault via llvm-commits]

================
@@ -223,17 +223,104 @@ void InstrInfoEmitter::EmitOperandInfo(raw_ostream &OS,
   }
 }
 
+static void emitGetInstructionIndexForOpLookup(
+    raw_ostream &OS, const MapVector<SmallVector<int>, unsigned> &OperandMap,
+    ArrayRef<unsigned> InstructionIndex) {
+  StringRef Type = OperandMap.size() <= UINT8_MAX + 1 ? "uint8_t" : "uint16_t";
+  OS << "LLVM_READONLY static " << Type
+     << " getInstructionIndexForOpLookup(uint16_t Opcode) {\n"
+        "  static constexpr "
+     << Type << " InstructionIndex[] = {";
+  for (auto [TableIndex, Entry] : enumerate(InstructionIndex))
+    OS << (TableIndex % 16 == 0 ? "\n    " : " ") << Entry << ',';
+  OS << "\n  };\n"
+        "  return InstructionIndex[Opcode];\n"
+        "}\n";
+}
+
+static void
+emitGetNamedOperandIdx(raw_ostream &OS,
+                       const MapVector<SmallVector<int>, unsigned> &OperandMap,
+                       unsigned MaxOperandNo, unsigned NumOperandNames) {
+  OS << "LLVM_READONLY int16_t getNamedOperandIdx(uint16_t Opcode, OpName "
+        "Name) {\n";
+  OS << "  assert(Name != OpName::NUM_OPERAND_NAMES);\n";
+  if (!NumOperandNames) {
+    // There are no operands, so no need to emit anything
+    OS << "  return -1;\n}\n";
+    return;
+  }
+  assert(MaxOperandNo <= INT16_MAX &&
+         "Too many operands for the operand name -> index table");
+  StringRef Type = MaxOperandNo <= INT8_MAX ? "int8_t" : "int16_t";
+  OS << "  static constexpr " << Type << " OperandMap[][" << NumOperandNames
+     << "] = {\n";
+  for (const auto &[OpList, _] : OperandMap) {
+    // Emit a row of the OperandMap table.
+    OS << "    {";
+    for (unsigned ID = 0; ID < NumOperandNames; ++ID)
+      OS << (ID < OpList.size() ? OpList[ID] : -1) << ", ";
+    OS << "},\n";
+  }
+  OS << "  };\n";
+
+  OS << "  unsigned InstrIdx = getInstructionIndexForOpLookup(Opcode);\n";
+  OS << "  return OperandMap[InstrIdx][(unsigned)Name];\n";
+  OS << "}\n";
+}
+
+static void
+emitGetOperandIdxName(raw_ostream &OS,
+                      MapVector<StringRef, unsigned> OperandNameToID,
+                      const MapVector<SmallVector<int>, unsigned> &OperandMap,
+                      unsigned MaxNumOperands, unsigned NumOperandNames) {
+  OS << "LLVM_READONLY OpName getOperandIdxName(uint16_t Opcode, int16_t Idx) "
+        "{\n";
+  OS << "  assert(Idx >= 0 && Idx < " << MaxNumOperands << ");\n";
+  if (!MaxNumOperands) {
+    // There are no operands, so no need to emit anything
+    OS << "  return -1;\n}\n";
+    return;
+  }
+  OS << "  static constexpr OpName OperandMap[][" << MaxNumOperands
+     << "] = {\n";
+  for (const auto &[OpList, _] : OperandMap) {
+    SmallVector<unsigned> IDs(MaxNumOperands, NumOperandNames);
+    for (const auto &[ID, Idx] : enumerate(OpList)) {
+      if (Idx >= 0)
+        IDs[Idx] = ID;
+    }
+    // Emit a row of the OperandMap table. Map operand indices to enum values.
+    OS << "    {";
+    for (unsigned ID : IDs) {
+      if (ID == NumOperandNames)
+        OS << "OpName::NUM_OPERAND_NAMES, ";
+      else
+        OS << "OpName::" << OperandNameToID.getArrayRef()[ID].first << ", ";
+    }
+    OS << "},\n";
+  }
+  OS << "  };\n";
+
+  OS << "  unsigned InstrIdx = getInstructionIndexForOpLookup(Opcode);\n";
+  OS << "  return OperandMap[InstrIdx][(unsigned)Idx];\n";
+  OS << "}\n";
----------------
arsenm wrote:

```suggestion
  OS << "  unsigned InstrIdx = getInstructionIndexForOpLookup(Opcode);\n"
              "  return OperandMap[InstrIdx][(unsigned)Idx];\n"
              "}\n";
```
Also should probably switch to raw string literals 

https://github.com/llvm/llvm-project/pull/154944