[llvm] [TableGen][CallingConv] Add CCAssignToRegTuple for synthetic registers. (PR #137826)

[Rahul Joshi via llvm-commits]

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@@ -35,14 +37,20 @@ class CallingConvEmitter {
   std::map<std::string, std::set<std::string>> DelegateToMap;
 
 public:
-  explicit CallingConvEmitter(const RecordKeeper &R) : Records(R) {}
+  explicit CallingConvEmitter(const RecordKeeper &R) : Records(R), Target(R) {
+    for (const CodeGenRegister &Reg : Target.getRegBank().getRegisters())
+      RegistersByDefName.try_emplace(Reg.getName(), &Reg);
+  }
 
   void run(raw_ostream &O);
 
 private:
   void emitCallingConv(const Record *CC, raw_ostream &O);
   void emitAction(const Record *Action, indent Indent, raw_ostream &O);
   void emitArgRegisterLists(raw_ostream &O);
+
+  StringMap<const CodeGenRegister *> RegistersByDefName;
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jurahul wrote:

I looked at this a bit more just for my understanding: It seems "RegisterTuples" are expanded in `CodeGenRegBank` constructor to synthesize the actual register records, and then synthesized records are never added back to `RecordKeeper`, hence the lookup path I suggested will fail. @nvjle is that correct? 

https://github.com/llvm/llvm-project/pull/137826