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[AsmParser][SystemZ][z/OS] Implement HLASM location counter syntax ("*") for Z…

Authored by anirudhp on May 3 2021, 11:57 AM.

Description

[AsmParser][SystemZ][z/OS] Implement HLASM location counter syntax ("*") for Z PC-relative instructions.

  • 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