[llvm] [X86][GISel] Fix crash on bitcasting i16 <-> half with gisel enabled. (PR #168456)

[Simon Pilgrim via llvm-commits]

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@@ -312,6 +312,55 @@ bool X86InstructionSelector::selectCopy(MachineInstr &I,
       }
     }
 
+    const int RegBankSize = 16;
+
+    // Special case GPR16 -> XMM
+    if (SrcSize == RegBankSize && SrcRegBank.getID() == X86::GPRRegBankID &&
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RKSimon wrote:

TBH I'd prefer we ditch RegBankSize and just put 16 in the condition directly - especially as RegBankSize doesn't hint at the size at all.
```suggestion
    if (SrcSize == 16 && SrcRegBank.getID() == X86::GPRRegBankID &&
```

https://github.com/llvm/llvm-project/pull/168456