[llvm] [CodeGen] Precompute untyped getMinimalPhysRegClass (PR #193438)

[Sander de Smalen via llvm-commits]

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@@ -829,6 +829,14 @@ class LLVM_ABI TargetRegisterInfo : public MCRegisterInfo {
     return nullptr;
   }
 
+  /// Return the target-defined minimal register class for an untyped physical
+  /// register query.
+  /// Will be nullptr if the register is not in any register class.
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sdesmalen-arm wrote:

```suggestion
  /// register query or nullptr if the register is not in any register class.
```

https://github.com/llvm/llvm-project/pull/193438