Most assemblers treat '<' and '>' as byte-select operators. Merlin 32
treats them as shift operators, making '<' effectively a no-op. A
mask is applied based on the length implied by the opcode or pseudo-op,
e.g. "DFB <FOO" will mask off the high bits. This is problematic for
instructions like "LDA <FOO", where the choice between absolute and DP
addressing depends on the value of "<FOO". If FOO is >= $100, the
lack of masking will cause it be treated as absolute. There is
currently no other mechanism to force the use of a direct-page opcode.
The only recourse is to append "&$ff" to the operand, so the
assembler knows that it can be handled as a DP op. The code generator
has been updated to add "&$ff" where needed, based on the label's
value. Unfortunately the assembler doesn't accept this for certain
specific addressing modes; this appears to be a bug.
The relevant test cases (2003x-labels-and-symbols) have been updated
to exercise these situations. The current test projects side-step the
failing assembler behavior by using a DP label instead. These should
be changed to correctly exercise the full behavior, with the code
generator outputting the instructions as raw hex values to work
around bugs.
There are some deliberately broken things (like a duplicate label) in
the 20030 case that were copied into the 20032 case when it was
created. For ease of editing these have been removed from 20032.
(issue #170)
Add a 6502-only version of the 20032-labels-and-symbols test. The
65816 version could get away with just the 65816-specific stuff, but
there's no real need to modify it. (The next time I update it I may
remove the duplicate label since that requires hand-editing.)
Andy McFadden