/*
* arch/xtensa/lib/strnlen_user.S
*
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file "COPYING" in the main directory of
* this archive for more details.
*
* Returns strnlen, including trailing zero terminator.
* Zero indicates error.
*
* Copyright (C) 2002 Tensilica Inc.
*/
#include <variant/core.h>
/* Load or store instructions that may cause exceptions use the EX macro. */
#define EX(insn,reg1,reg2,offset,handler) \
9: insn reg1, reg2, offset; \
.section __ex_table, "a"; \
.word 9b, handler; \
.previous
/*
* size_t __strnlen_user(const char *s, size_t len)
*/
#ifdef __XTENSA_EB__
# define MASK0 0xff000000
# define MASK1 0x00ff0000
# define MASK2 0x0000ff00
# define MASK3 0x000000ff
#else
# define MASK0 0x000000ff
# define MASK1 0x0000ff00
# define MASK2 0x00ff0000
# define MASK3 0xff000000
#endif
# Register use:
# a2/ src
# a3/ len
# a4/ tmp
# a5/ mask0
# a6/ mask1
# a7/ mask2
# a8/ mask3
# a9/ tmp
# a10/ tmp
.text
.align 4
.global __strnlen_user
.type __strnlen_user,@function
__strnlen_user:
entry sp, 16 # minimal stack frame
# a2/ s, a3/ len
addi a4, a2, -4 # because we overincrement at the end;
# we compensate with load offsets of 4
movi a5, MASK0 # mask for byte 0
movi a6, MASK1 # mask for byte 1
movi a7, MASK2 # mask for byte 2
movi a8, MASK3 # mask for byte 3
bbsi.l a2, 0, .L1mod2 # if only 8-bit aligned
bbsi.l a2, 1, .L2mod4 # if only 16-bit aligned
/*
* String is word-aligned.
*/
.Laligned:
srli a10, a3, 2 # number of loop iterations with 4B per loop
#if XCHAL_HAVE_LOOPS
loopnez a10, .Ldone
#else
beqz a10, .Ldone
slli a10, a10, 2
add a10, a10, a4 # a10 = end of last 4B chunk
#endif /* XCHAL_HAVE_LOOPS */
.Loop:
EX(l32i, a9, a4, 4, lenfixup) # get next word of string
addi a4, a4, 4 # advance string pointer
bnone a9, a5, .Lz0 # if byte 0 is zero
bnone a9, a6, .Lz1 # if byte 1 is zero
bnone a9, a7, .Lz2 # if byte 2 is zero
bnone a9, a8, .Lz3 # if byte 3 is zero
#if !XCHAL_HAVE_LOOPS
blt a4, a10, .Loop
#endif
.Ldone:
EX(l32i, a9, a4, 4, lenfixup) # load 4 bytes for remaining checks
bbci.l a3, 1, .L100
# check two more bytes (bytes 0, 1 of word)
addi a4, a4, 2 # advance string pointer
bnone a9, a5, .Lz0 # if byte 0 is zero
bnone a9, a6, .Lz1 # if byte 1 is zero
.L100:
bbci.l a3, 0, .L101
# check one more byte (byte 2 of word)
# Actually, we don't need to check. Zero or nonzero, we'll add one.
# Do not add an extra one for the NULL terminator since we have
# exhausted the original len parameter.
addi a4, a4, 1 # advance string pointer
.L101:
sub a2, a4, a2 # compute length
retw
# NOTE that in several places below, we point to the byte just after
# the zero byte in order to include the NULL terminator in the count.
.Lz3: # byte 3 is zero
addi a4, a4, 3 # point to zero byte
.Lz0: # byte 0 is zero
addi a4, a4, 1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.Lz1: # byte 1 is zero
addi a4, a4, 1+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.Lz2: # byte 2 is zero
addi a4, a4, 2+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.L1mod2: # address is odd
EX(l8ui, a9, a4, 4, lenfixup) # get byte 0
addi a4, a4, 1 # advance string pointer
beqz a9, .Lz3 # if byte 0 is zero
bbci.l a4, 1, .Laligned # if string pointer is now word-aligned
.L2mod4: # address is 2 mod 4
addi a4, a4, 2 # advance ptr for aligned access
EX(l32i, a9, a4, 0, lenfixup) # get word with first two bytes of string
bnone a9, a7, .Lz2 # if byte 2 (of word, not string) is zero
bany a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero
# byte 3 is zero
addi a4, a4, 3+1 # point just beyond zero byte
sub a2, a4, a2 # subtract to get length
retw
.section .fixup, "ax"
.align 4
lenfixup:
movi a2, 0
retw
