Mistaken alternative mnemonics

[Rangi42]

https://gbdev.io/gb-opcodes/optables/classic claims:

• LDH A, [a8] has the alternative mnemonic LD A, [$FF00+a8]
• LDH [a8], A has the alternative mnemonic LD [$FF00+a8], A

These are not true; a8 is "8-bit unsigned data", and $FF00+a8 just results in a single number $FFa8 which does not get auto-converted from LD to LDH.

[Rangi42]

The table also shows LD [C], A / LD A, [C] as the "primary" instructions, with LD A, [$FF00+C] / LD [$FF00+C], A listed as alternative mnemonics and LDH [C], A / LDH A, [C] not even mentioned as possible. I think LDH should be "primary" with LD and $FF00+ listed as the alternatives.

[Rangi42]

Furthermore, LDHL SP, e8 is listed as an alternative for LD HL, SP+e8, when RGBASM has never supported LDHL. (Apparently ASMotor did, but it was removed by RGBDS 0.1.0.)

[nummacway]

The table also shows LD [C], A / LD A, [C] as the "primary" instructions

Even though I usually like backwards compatibility, I would call this notation "plain wrong". To me, it suggests that it addressed $0000 to $00FF, when in fact it addresses $FF00 to $FFFF.
I agree that LDH should be the preferred syntax for consistency with what you say in OP.

[aaaaaa123456789]

The ld a, [c] notation is just derived from the official syntax, I believe. But ldh a, [c] should definitely be the preferred form.

[Rangi42]

The "official" syntax is also (deref) and ldhl and jp (hl). Given that we never even supported ldhl, maybe we should deprecate ld [c] too.

[Rangi42]

Remaining non-deprecated redundant syntaxes as of 0.9.0:

• ldi/ldd [hl] vs ld [hli/hld] vs ld [hl+/hl-]
• ldh [c] vs ld [c] vs ld [$ff00+c] (but can we deprecate ld [c] too?)
• ldh [a8] vs ld [$ff00+a8]

[ISSOtm]

I think only the first of these ought to remain, and $ff00+c as seen in gbdev/rgbds#1567. We've deprecated the second and third bullets.

[Rangi42]

Yes, 0.9.0 will have deprecated ld [c] and ldh [a8]. That leaves:

• ldi/ldd [hl] vs ld [hli/hld] vs ld [hl+/hl-] (all of which get used by someone)
• ldh [c] vs ld [$ff00+c] (a poll found 7 votes to keep ld [$ff00+c] vs 9 to deprecate it)
• ldh [a8] (ld [$ff00+a8] is not even an alias, just a mistaken in the docs here, and absolutely should be corrected)