mirror of
https://github.com/autc04/Retro68.git
synced 2024-09-01 16:29:41 +00:00
33 lines
875 B
ArmAsm
33 lines
875 B
ArmAsm
.file "memchr.S"
|
|
|
|
.section .text
|
|
|
|
.global _memchr
|
|
.type _memchr,@function
|
|
_memchr:
|
|
;; R1: string pointer
|
|
;; R2: byte sought
|
|
;; R3: max number to scan
|
|
#ifdef __RX_DISALLOW_STRING_INSNS__
|
|
mov.b r2, r2 ; The mov.b below sign extends as it loads, so make sure that r2 is sign-extended as well.
|
|
2: cmp #0, r3
|
|
beq 1f
|
|
sub #1, r3
|
|
mov.b [r1+], r5
|
|
cmp r5, r2
|
|
bne 2b
|
|
|
|
sub #1, r1 ; We have found a match, bit now R1 points to the byte after the match.
|
|
1: rts
|
|
#else
|
|
cmp #0, r3 ; If r3 is 0 suntil.b will do nothing and not set any flags...
|
|
stz #1, r1 ; ...so store 1 into r1. It will be decremented by the SUB later.
|
|
suntil.b ; Search until *r1 == r2 or r3 bytes have been examined.
|
|
stnz #1, r1 ; If no match was found return NULL.
|
|
sub #1, r1 ; suntil.b leaves r1 pointing at the address *after* the match.
|
|
rts
|
|
#endif
|
|
|
|
.size _memchr, . - _memchr
|
|
|