xref: /freebsd/contrib/cortex-strings/src/arm/strchr.S (revision 8c4282b370bd66908b45b6a223226a9fc2b69d57)

/* Copyright (c) 2010-2011, Linaro Limited
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/*
   Written by Dave Gilbert <david.gilbert@linaro.org>

   A very simple strchr routine, from benchmarks on A9 it's a bit faster than
   the current version in eglibc (2.12.1-0ubuntu14 package)
   I don't think doing a word at a time version is worth it since a lot
   of strchr cases are very short anyway.

 */

@ 2011-02-07 david.gilbert@linaro.org
@    Extracted from local git a5b438d861

	.syntax unified
	.arch armv7-a

	.text
	.thumb

@ ---------------------------------------------------------------------------

	.thumb_func
	.align 2
	.p2align 4,,15
	.global strchr
	.type strchr,%function
strchr:
	@ r0 = start of string
	@ r1 = character to match
	@ returns NULL for no match, or a pointer to the match
	and	r1,r1, #255

1:
	ldrb	r2,[r0],#1
	cmp	r2,r1
	cbz	r2,10f
	bne	1b

	@ We're here if it matched
5:
	subs	r0,r0,#1
	bx	lr

10:
	@ We're here if we ran off the end
	cmp	r1, #0	@ Corner case - you're allowed to search for the nil and get a pointer to it
	beq	5b	@ A bit messy, if it's common we should branch at the start to a special loop
	mov	r0,#0
	bx	lr