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avra: generalize arg swapping behavior

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This commit is contained in:
Virgil Dupras 2019-12-15 16:36:43 -05:00
parent 14fbfa2967
commit 20861767e6
1 changed files with 23 additions and 13 deletions
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36
apps/zasm/avr.asm
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@ -121,7 +121,14 @@ instrNames:
; index (1-based, 0 means no arg) in the argSpecs table. High nibble is for
; flags. Meaning:
;
; (None for now)
; Bit 7: Arguments swapped. For example, if we have this bit set on the argspec
; row 'A', 'R', then what will actually be read is 'R', 'A'. The
; arguments destination will be, hum, de-swapped, that is, 'A' is going
; in H and 'R' is going in L. This is used, for example, with IN and OUT.
; IN has a Rd(5), A(6) signature. OUT could have the same signature, but
; AVR's mnemonics has those args reversed for more consistency
; (destination is always the first arg). The goal of this flag is to
; allow this kind of syntactic sugar with minimal complexity.
; In the same order as in instrNames
instrTbl:
@ -157,8 +164,8 @@ instrTbl:
.db 0x00, 0b11010000, 0x00 ; RCALL
.db 0x00, 0b11000000, 0x00 ; RJMP
; IN and OUT
.db 0x08, 0b10110000, 0x00 ; IN
.db 0x07, 0b10111000, 0x00 ; OUT
.db 0x07, 0b10110000, 0x00 ; IN
.db 0x87, 0b10111000, 0x00 ; OUT (args reversed)
; no arg
.db 0x00, 0b10010101, 0b10011000 ; BREAK
.db 0x00, 0b10010100, 0b10001000 ; CLC
@ -273,6 +280,8 @@ parseInstruction:
ld a, (hl)
ld h, d
ld l, a ; H and L contain specs now
bit 7, (ix)
call nz, .swapHL ; Bit 7 set, swap H and L
call _parseArgs
ret nz
.noarg:
@ -280,6 +289,8 @@ parseInstruction:
; (IX) is table row
; Parse arg values now in H and L
; InstrID is E
bit 7, (ix)
call nz, .swapHL ; Bit 7 set, swap H and L again!
ld a, e ; InstrID
cp I_ANDI
jr c, .spitRd5Rr5
@ -289,9 +300,8 @@ parseInstruction:
jr c, .spitRdBit
cp I_IN
jr c, .spitK12
jp z, .spitIN
cp I_OUT
jp z, .spitOUT
cp I_BREAK
jp c, .spitINOUT
cp I_ASR
jp c, .spit ; no arg
; spitRd5
@ -368,12 +378,7 @@ parseInstruction:
or b
jp ioPutB
.spitOUT:
ld a, h
ld h, l
ld l, a
; Continue to spitIN
.spitIN:
.spitINOUT:
; Rd in H, A in L
ld a, h
call .placeRd
@ -463,6 +468,12 @@ parseInstruction:
ld c, a
ret
.swapHL:
ld a, h
ld h, l
ld l, a
ret
; Argspecs: two bytes describing the arguments that are accepted. Possible
; values:
;
@ -486,7 +497,6 @@ argSpecs:
.db 'r', 8 ; Rd(4) + K(8)
.db 'R', 'b' ; Rd(5) + bit
.db 'b', 7 ; bit + k(7)
.db 'A', 'R' ; A(6) + Rr(5)
.db 'R', 'A' ; Rd(5) + A(6)
; Parse arguments from I/O according to specs in HL