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GB: a few minor optimizations to the integer division routines

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Toxa
2026-01-13 19:23:54 +03:00
parent a51b4e04cc
commit bab52712cf
1 changed files with 11 additions and 10 deletions
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21
gbdk-lib/libc/asm/sm83/div.s
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@@ -260,8 +260,7 @@ signexte:
ld d,a
ret
.exit:
pop af
pop af
add sp, #4
ret
.divu8::
@@ -275,13 +274,8 @@ signexte:
;; Check for division by zero
ld a,e
or d
jr NZ,.divide ; Branch if divisor is non-zero
ld bc,#0x00 ; Divide by zero error
ld d,b
ld e,c
scf ; Set carry, invalid result
ret
.divide:
jr Z,.error ; Branch if divisor is zero
ld l,c ; L = low byte of dividend/quotient
ld h,b ; H = high byte of dividend/quotient
ld bc,#0x00 ; BC = remainder
@@ -319,13 +313,14 @@ signexte:
or a ; restore (clear) the carry flag
jr NZ,.dvloop
jr .nodrop
.drop:
pop af ; faster and smaller than 2x inc sp
pop af ; recover # bits remaining, carry flag destroyed
dec a
scf ; restore (set) the carry flag
jr NZ,.dvloop
jr .nodrop
.nodrop:
;; Shift last carry bit into quotient
ld d,b ; DE = remainder
@@ -337,3 +332,9 @@ signexte:
or a ; Clear carry, valid result
ret
.error:
ld bc,#0x00 ; Divide by zero error
ld d,b
ld e,c
scf ; Set carry, invalid result
ret