[NFC][TableGen] Change RecordKeeper::getDef() to return const pointer (#110992)

This is a part of effort to have better const correctness in TableGen
backends:


https://discourse.llvm.org/t/psa-planned-changes-to-tablegen-getallderiveddefinitions-api-potential-downstream-breakages/81089

Author: jurahul

llvm/include/llvm/TableGen/Record.h

@@ -1993,14 +1993,14 @@ class RecordKeeper {
   }
 
   /// Get the concrete record with the specified name.
-  Record *getDef(StringRef Name) const {
+  const Record *getDef(StringRef Name) const {
     auto I = Defs.find(Name);
     return I == Defs.end() ? nullptr : I->second.get();
   }
 
   /// Get the \p Init value of the specified global variable.
   Init *getGlobal(StringRef Name) const {
-    if (Record *R = getDef(Name))
+    if (const Record *R = getDef(Name))
       return R->getDefInit();
     auto It = ExtraGlobals.find(Name);
     return It == ExtraGlobals.end() ? nullptr : It->second;

llvm/lib/TableGen/Record.cpp

@@ -871,7 +871,7 @@ Init *UnOpInit::Fold(Record *CurRec, bool IsFinal) const {
 
     } else if (isa<RecordRecTy>(getType())) {
       if (StringInit *Name = dyn_cast<StringInit>(LHS)) {
-        Record *D = RK.getDef(Name->getValue());
+        const Record *D = RK.getDef(Name->getValue());
         if (!D && CurRec) {
           // Self-references are allowed, but their resolution is delayed until
           // the final resolve to ensure that we get the correct type for them.
@@ -2113,7 +2113,7 @@ Init *ExistsOpInit::Fold(Record *CurRec, bool IsFinal) const {
   if (StringInit *Name = dyn_cast<StringInit>(Expr)) {
 
     // Look up all defined records to see if we can find one.
-    Record *D = CheckType->getRecordKeeper().getDef(Name->getValue());
+    const Record *D = CheckType->getRecordKeeper().getDef(Name->getValue());
     if (D) {
       // Check if types are compatible.
       return IntInit::get(getRecordKeeper(),

llvm/lib/TableGen/SetTheory.cpp

@@ -222,7 +222,7 @@ struct SequenceOp : public SetTheory::Operator {
       std::string Name;
       raw_string_ostream OS(Name);
       OS << format(Format.c_str(), unsigned(From));
-      Record *Rec = Records.getDef(Name);
+      const Record *Rec = Records.getDef(Name);
       if (!Rec)
         PrintFatalError(Loc, "No def named '" + Name + "': " +
           Expr->getAsString());

llvm/lib/TableGen/TGParser.cpp

@@ -541,7 +541,7 @@ bool TGParser::resolve(const std::vector<RecordsEntry> &Source,
 /// Resolve the record fully and add it to the record keeper.
 bool TGParser::addDefOne(std::unique_ptr<Record> Rec) {
   Init *NewName = nullptr;
-  if (Record *Prev = Records.getDef(Rec->getNameInitAsString())) {
+  if (const Record *Prev = Records.getDef(Rec->getNameInitAsString())) {
     if (!Rec->isAnonymous()) {
       PrintError(Rec->getLoc(),
                  "def already exists: " + Rec->getNameInitAsString());
@@ -1108,7 +1108,7 @@ const RecTy *TGParser::ParseType() {
       Lex.Lex();
       return I->second;
     }
-    if (Record *R = ParseClassID())
+    if (const Record *R = ParseClassID())
       return RecordRecTy::get(R);
     TokError("unknown class name");
     return nullptr;

llvm/unittests/TableGen/ParserEntryPointTest.cpp

@@ -33,7 +33,7 @@ TEST(Parser, SanityTest) {
   bool ProcessResult = TableGenParseFile(SrcMgr, Records);
   EXPECT_FALSE(ProcessResult);
 
-  Record *Foo = Records.getDef("Foo");
+  const Record *Foo = Records.getDef("Foo");
   std::optional<StringRef> Field = Foo->getValueAsOptionalString("strField");
   EXPECT_TRUE(Field.has_value());
   EXPECT_EQ(*Field, "value");

llvm/utils/TableGen/Common/CodeGenSchedule.cpp

@@ -532,8 +532,8 @@ void CodeGenSchedModels::collectProcModels() {
   ProcModels.reserve(ProcRecords.size() + 1);
 
   // Use idx=0 for NoModel/NoItineraries.
-  Record *NoModelDef = Records.getDef("NoSchedModel");
-  Record *NoItinsDef = Records.getDef("NoItineraries");
+  const Record *NoModelDef = Records.getDef("NoSchedModel");
+  const Record *NoItinsDef = Records.getDef("NoItineraries");
   ProcModels.emplace_back(0, "NoSchedModel", NoModelDef, NoItinsDef);
   ProcModelMap[NoModelDef] = 0;