[PATCH] D73176: [ARM] Fix dropped dollar sign from symbols in branch targets

[Lucas Prates via Phabricator via llvm-commits]

pratlucas added a comment.

Regarding the `b $4` case, I found that the limitation currently lies in the expression/identifier parsing at the core AsmParser, which only detects $-prefixed `Identifier` or `String` tokens at the moment.
As this part of the code has no knowledge of the branch instruction context, I'm afraid updating it to accept `Integer` tokens as well might cause some inconsistencies in the instructions for which we drop the leading `Dollar` token. For example:

  # Branch instructions consistently treat $<integere> as identifier
  b   $4                  @ b ($4)         - Symbol
  b   $4 + $4             @ b #($4)+($4)   - Symbol
  # Other instructions treat those as identifiers only when they're
  # on the begining of the operand
  movw  r0, $4            @ movw r0, #4            - Immediate constant
  movw  r0, :lower16:$4   @ movw r0, :lower16:($4) - Symbol

>From what I checked on the gas behavior, it seems to only treat those as constant immediates when actual constants are explicitly expected by the instruction. Otherwise it assumes those are identifiers.
Would you say the behavior above is the expected one? Or should we go for the alignment with gas' behavior?


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https://reviews.llvm.org/D73176