- This patch attempts to implement the location counter syntax (*) for the HLASM variant for PC-relative instructions.
- In the HLASM variant, for purely constant relocatable values, we expect a * token preceding it, with special support for " *" which is parsed as "<pc-rel-insn 0>"
- For combinations of absolute values and relocatable values, we don't expect the "*" preceding the token.
When you have a " * " what’s accepted is:
```
*<space>.*{.*} -> <pc-rel-insn> 0
*[+|-][constant-value] -> <pc-rel-insn> [+|-]constant-value
```
When you don’t have a " * " what’s accepted is:
```
brasl 1,func is allowed (MCSymbolRef type)
brasl 1,func+4 is allowed (MCBinary type)
brasl 1,4+func is allowed (MCBinary type)
brasl 1,-4+func is allowed (MCBinary type)
brasl 1,func-4 is allowed (MCBinary type)
brasl 1,*func is not allowed (* cannot be used for non-MCConstantExprs)
brasl 1,*+func is not allowed (* cannot be used for non-MCConstantExprs)
brasl 1,*+func+4 is not allowed (* cannot be used for non-MCConstantExprs)
brasl 1,*+4+func is not allowed (* cannot be used for non-MCConstantExprs)
brasl 1,*-4+8+func is not allowed (* cannot be used for non-MCConstantExprs)
```
Reviewed By: Kai
Differential Revision: https://reviews.llvm.org/D100987
ca02fab7e7