[llvm] [X86] Support EGPR (R16-R31) for APX (PR #67702)

[Phoebe Wang via llvm-commits]

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@@ -158,6 +158,10 @@ X86RegisterInfo::getLargestLegalSuperClass(const TargetRegisterClass *RC,
     case X86::GR16RegClassID:
     case X86::GR32RegClassID:
     case X86::GR64RegClassID:
+    case X86::GR8_NOREX2RegClassID:
+    case X86::GR16_NOREX2RegClassID:
+    case X86::GR32_NOREX2RegClassID:
+    case X86::GR64_NOREX2RegClassID:
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phoebewang wrote:

It's not clear to me when we need to distinguish `X86::GR8_NOREX2RegClassID` from `X86::GR8RegClassID` and when not. We have some other places, e.g., [here ](https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/X86/X86InsertPrefetch.cpp#L87-L91)that using `X86::GRxxRegClassID`, shouldn't need to update with `X86::GRxx_NOREX2RegClassID`
Besides, we also have some place to `createVirtualRegister(&X86::GRxxRegClass)`, should they need to update too?

https://github.com/llvm/llvm-project/pull/67702