[llvm] CodeGen: Add RegisterClass by HwMode (PR #158269)

[Craig Topper via llvm-commits]

================
@@ -916,15 +922,30 @@ def decoder;
 /// derived from this. TableGen treats the register class as having a symbolic
 /// type that it doesn't know, and resolves the actual regclass to use by using
 /// the TargetRegisterInfo::getPointerRegClass() hook at codegen time.
+///
+/// This is deprecated in favor of RegClassByHwMode.
 class PointerLikeRegClass<int Kind> {
   int RegClassKind = Kind;
 }
 
+/// RegClassByHwMode - Operands that change the register class based
+/// on the subtarget are derived from this derived from this. TableGen
----------------
topperc wrote:

```suggestion
/// on the subtarget are derived from this. TableGen
```

https://github.com/llvm/llvm-project/pull/158269