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Lots of minor optimisations

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Removed an unecessary conditional jump in main.asm, saving 7 cycles and 2 bytes. Removed a function called "subDEfromHL" or something like that, and replaced it with `sbc hl, de`, saving 10 bytes total and 61 cycles. I also rewrote enterParens and strlen to use cpir instead of cpi in a loop, saving 14 cycles per character and also 6 bytes (bc needed to be zeroed in enterParens).
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Clanmaster21 2019-10-17 20:33:01 +01:00 committed by GitHub
parent c255903323
commit 6c0052578e
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3 changed files with 10 additions and 27 deletions
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6
apps/zasm/instr.asm
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@ -739,12 +739,14 @@ getUpcode:
push de ; Don't let go of this, that's our dest push de ; Don't let go of this, that's our dest
push hl push hl
call zasmGetPC ; --> HL call zasmGetPC ; --> HL
ex de, hl ex de, hl ; zasmGetPC sets carry on add hl, de
; Since it's a PC value, a carry would mean we've overflowed memory.
; That means we can safely assume the carry is unset.
pop hl pop hl
call intoHL call intoHL
dec hl ; what we write is "e-2" dec hl ; what we write is "e-2"
dec hl dec hl
call subDEFromHL sbc hl, de ; flags don't need preserving, and carry unset
pop de ; Still have it? good pop de ; Still have it? good
; HL contains our number and we'll check its bounds. If It's negative, ; HL contains our number and we'll check its bounds. If It's negative,
; H is going to be 0xff and L has to be >= 0x80. If it's positive, ; H is going to be 0xff and L has to be >= 0x80. If it's positive,

3
apps/zasm/main.asm
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@ -115,8 +115,7 @@ zasmParseFile:
ret nz ; error ret nz ; error
ld a, b ; TOK_* ld a, b ; TOK_*
cp TOK_EOF cp TOK_EOF
jr z, .eof jr nz, .loop
jr .loop
.eof: .eof:
call zasmIsLocalPass call zasmIsLocalPass
jr nz, .end ; EOF and not local pass jr nz, .end ; EOF and not local pass

28
apps/zasm/util.asm
View File

@ -12,18 +12,6 @@ callHL:
jp (hl) jp (hl)
ret ret
; HL - DE -> HL
subDEFromHL:
push af
ld a, l
sub e
ld l, a
ld a, h
sbc a, d
ld h, a
pop af
ret
; make Z the opposite of what it is now ; make Z the opposite of what it is now
toggleZ: toggleZ:
jp z, unsetZ jp z, unsetZ
@ -37,17 +25,13 @@ strlen:
push hl push hl
ld bc, 0 ld bc, 0
ld a, 0 ; look for null char ld a, 0 ; look for null char
.loop: cpir
cpi
jp z, .found
jr .loop
.found: .found:
; How many char do we have? the (NEG BC)-1, which started at 0 and ; How many char do we have? the (NEG BC)-1, which started at 0 and
; decreased at each CPI call. In this routine, we stay in the 8-bit ; decreased at each CPI call. In this routine, we stay in the 8-bit
; realm, so C only. ; realm, so C only.
ld a, c ld a, c
neg cpl ; -a = (~a)+1, so (-a)-1 = ~a
dec a
pop hl pop hl
pop bc pop bc
ret ret
@ -132,12 +116,10 @@ enterParens:
cp '(' cp '('
ret nz ; nothing to do ret nz ; nothing to do
push hl push hl
ld a, 0 ; look for null char ld bc, 0 ; so we can use cpir
ld a, b ; look for null char
; advance until we get null ; advance until we get null
.loop: cpir
cpi
jp z, .found
jr .loop
.found: .found:
dec hl ; cpi over-advances. go back to null-char dec hl ; cpi over-advances. go back to null-char
dec hl ; looking at the last char before null dec hl ; looking at the last char before null