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/* Optimized strcmp for Xtensa.
Copyright (C) 2001, 2007 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
Boston, MA 02110-1301, USA. */
#include <sysdep.h>
#include <bits/xtensa-config.h>
#include <features.h>
#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
#define MASK4 0x40404040
.literal .Lmask0, MASK0
.literal .Lmask1, MASK1
.literal .Lmask2, MASK2
.literal .Lmask3, MASK3
.literal .Lmask4, MASK4
.text
ENTRY (strcmp)
/* a2 = s1, a3 = s2 */
l8ui a8, a2, 0 /* byte 0 from s1 */
l8ui a9, a3, 0 /* byte 0 from s2 */
movi a10, 3 /* mask */
bne a8, a9, .Lretdiff
or a11, a2, a3
bnone a11, a10, .Laligned
xor a11, a2, a3 /* compare low two bits of s1 and s2 */
bany a11, a10, .Lunaligned /* if they have different alignment */
/* s1/s2 are not word-aligned. */
addi a2, a2, 1 /* advance s1 */
beqz a8, .Leq /* bytes equal, if zero, strings are equal */
addi a3, a3, 1 /* advance s2 */
bnone a2, a10, .Laligned /* if s1/s2 now aligned */
l8ui a8, a2, 0 /* byte 1 from s1 */
l8ui a9, a3, 0 /* byte 1 from s2 */
addi a2, a2, 1 /* advance s1 */
bne a8, a9, .Lretdiff /* if different, return difference */
beqz a8, .Leq /* bytes equal, if zero, strings are equal */
addi a3, a3, 1 /* advance s2 */
bnone a2, a10, .Laligned /* if s1/s2 now aligned */
l8ui a8, a2, 0 /* byte 2 from s1 */
l8ui a9, a3, 0 /* byte 2 from s2 */
addi a2, a2, 1 /* advance s1 */
bne a8, a9, .Lretdiff /* if different, return difference */
beqz a8, .Leq /* bytes equal, if zero, strings are equal */
addi a3, a3, 1 /* advance s2 */
j .Laligned
/* s1 and s2 have different alignment.
If the zero-overhead loop option is available, use an (almost)
infinite zero-overhead loop with conditional exits so we only pay
for taken branches when exiting the loop.
Note: It is important for this unaligned case to come before the
code for aligned strings, because otherwise some of the branches
above cannot reach and have to be transformed to branches around
jumps. The unaligned code is smaller and the branches can reach
over it. */
.align 4
/* (2 mod 4) alignment for loop instruction */
.Lunaligned:
#if XCHAL_HAVE_LOOPS
_movi.n a8, 0 /* set up for the maximum loop count */
loop a8, .Lretdiff /* loop forever (almost anyway) */
#endif
.Lnextbyte:
l8ui a8, a2, 0
l8ui a9, a3, 0
addi a2, a2, 1
bne a8, a9, .Lretdiff
addi a3, a3, 1
#if XCHAL_HAVE_LOOPS
beqz a8, .Lretdiff
#else
bnez a8, .Lnextbyte
#endif
.Lretdiff:
sub a2, a8, a9
retw
/* s1 is word-aligned; s2 is word-aligned.
If the zero-overhead loop option is available, use an (almost)
infinite zero-overhead loop with conditional exits so we only pay
for taken branches when exiting the loop. */
/* New algorithm, relying on the fact that all normal ASCII is between
32 and 127.
Rather than check all bytes for zero:
Take one word (4 bytes). Call it w1.
Shift w1 left by one into w1'.
Or w1 and w1'. For all normal ASCII bit 6 will be 1; for zero it won't.
Check that all 4 bit 6's (one for each byte) are one:
If they are, we are definitely not done.
If they are not, we are probably done, but need to check for zero. */
.align 4
#if XCHAL_HAVE_LOOPS
.Laligned:
.begin no-transform
l32r a4, .Lmask0 /* mask for byte 0 */
l32r a7, .Lmask4
/* Loop forever. (a4 is more than than the maximum number
of iterations) */
loop a4, .Laligned_done
/* First unrolled loop body. */
l32i a8, a2, 0 /* get word from s1 */
l32i a9, a3, 0 /* get word from s2 */
slli a5, a8, 1
bne a8, a9, .Lwne2
or a9, a8, a5
bnall a9, a7, .Lprobeq
/* Second unrolled loop body. */
l32i a8, a2, 4 /* get word from s1+4 */
l32i a9, a3, 4 /* get word from s2+4 */
slli a5, a8, 1
bne a8, a9, .Lwne2
or a9, a8, a5
bnall a9, a7, .Lprobeq2
addi a2, a2, 8 /* advance s1 pointer */
addi a3, a3, 8 /* advance s2 pointer */
.Laligned_done:
or a1, a1, a1 /* nop */
.Lprobeq2:
/* Adjust pointers to account for the loop unrolling. */
addi a2, a2, 4
addi a3, a3, 4
#else /* !XCHAL_HAVE_LOOPS */
.Laligned:
movi a4, MASK0 /* mask for byte 0 */
movi a7, MASK4
j .Lfirstword
.Lnextword:
addi a2, a2, 4 /* advance s1 pointer */
addi a3, a3, 4 /* advance s2 pointer */
.Lfirstword:
l32i a8, a2, 0 /* get word from s1 */
l32i a9, a3, 0 /* get word from s2 */
slli a5, a8, 1
bne a8, a9, .Lwne2
or a9, a8, a5
ball a9, a7, .Lnextword
#endif /* !XCHAL_HAVE_LOOPS */
/* align (0 mod 4) */
.Lprobeq:
/* Words are probably equal, but check for sure.
If not, loop over the rest of string using normal algorithm. */
bnone a8, a4, .Leq /* if byte 0 is zero */
l32r a5, .Lmask1 /* mask for byte 1 */
l32r a6, .Lmask2 /* mask for byte 2 */
bnone a8, a5, .Leq /* if byte 1 is zero */
l32r a7, .Lmask3 /* mask for byte 3 */
bnone a8, a6, .Leq /* if byte 2 is zero */
bnone a8, a7, .Leq /* if byte 3 is zero */
addi.n a2, a2, 4 /* advance s1 pointer */
addi.n a3, a3, 4 /* advance s2 pointer */
#if XCHAL_HAVE_LOOPS
/* align (1 mod 4) */
loop a4, .Leq /* loop forever (a4 is bigger than max iters) */
.end no-transform
l32i a8, a2, 0 /* get word from s1 */
l32i a9, a3, 0 /* get word from s2 */
addi a2, a2, 4 /* advance s1 pointer */
bne a8, a9, .Lwne
bnone a8, a4, .Leq /* if byte 0 is zero */
bnone a8, a5, .Leq /* if byte 1 is zero */
bnone a8, a6, .Leq /* if byte 2 is zero */
bnone a8, a7, .Leq /* if byte 3 is zero */
addi a3, a3, 4 /* advance s2 pointer */
#else /* !XCHAL_HAVE_LOOPS */
j .Lfirstword2
.Lnextword2:
addi a3, a3, 4 /* advance s2 pointer */
.Lfirstword2:
l32i a8, a2, 0 /* get word from s1 */
l32i a9, a3, 0 /* get word from s2 */
addi a2, a2, 4 /* advance s1 pointer */
bne a8, a9, .Lwne
bnone a8, a4, .Leq /* if byte 0 is zero */
bnone a8, a5, .Leq /* if byte 1 is zero */
bnone a8, a6, .Leq /* if byte 2 is zero */
bany a8, a7, .Lnextword2 /* if byte 3 is zero */
#endif /* !XCHAL_HAVE_LOOPS */
/* Words are equal; some byte is zero. */
.Leq: movi a2, 0 /* return equal */
retw
.Lwne2: /* Words are not equal. On big-endian processors, if none of the
bytes are zero, the return value can be determined by a simple
comparison. */
#ifdef __XTENSA_EB__
or a10, a8, a5
bnall a10, a7, .Lsomezero
bgeu a8, a9, .Lposreturn
movi a2, -1
retw
.Lposreturn:
movi a2, 1
retw
.Lsomezero: /* There is probably some zero byte. */
#endif /* __XTENSA_EB__ */
.Lwne: /* Words are not equal. */
xor a2, a8, a9 /* get word with nonzero in byte that differs */
bany a2, a4, .Ldiff0 /* if byte 0 differs */
movi a5, MASK1 /* mask for byte 1 */
bnone a8, a4, .Leq /* if byte 0 is zero */
bany a2, a5, .Ldiff1 /* if byte 1 differs */
movi a6, MASK2 /* mask for byte 2 */
bnone a8, a5, .Leq /* if byte 1 is zero */
bany a2, a6, .Ldiff2 /* if byte 2 differs */
bnone a8, a6, .Leq /* if byte 2 is zero */
#ifdef __XTENSA_EB__
.Ldiff3:
.Ldiff2:
.Ldiff1:
/* Byte 0 is equal (at least) and there is a difference before a zero
byte. Just subtract words to get the return value.
The high order equal bytes cancel, leaving room for the sign. */
sub a2, a8, a9
retw
.Ldiff0:
/* Need to make room for the sign, so can't subtract whole words. */
extui a10, a8, 24, 8
extui a11, a9, 24, 8
sub a2, a10, a11
retw
#else /* !__XTENSA_EB__ */
/* Little-endian is a little more difficult because can't subtract
whole words. */
.Ldiff3:
/* Bytes 0-2 are equal; byte 3 is different.
For little-endian need to have a sign bit for the difference. */
extui a10, a8, 24, 8
extui a11, a9, 24, 8
sub a2, a10, a11
retw
.Ldiff0:
/* Byte 0 is different. */
extui a10, a8, 0, 8
extui a11, a9, 0, 8
sub a2, a10, a11
retw
.Ldiff1:
/* Byte 0 is equal; byte 1 is different. */
extui a10, a8, 8, 8
extui a11, a9, 8, 8
sub a2, a10, a11
retw
.Ldiff2:
/* Bytes 0-1 are equal; byte 2 is different. */
extui a10, a8, 16, 8
extui a11, a9, 16, 8
sub a2, a10, a11
retw
#endif /* !__XTENSA_EB */
libc_hidden_def (strcmp)
#ifndef __UCLIBC_HAS_LOCALE__
strong_alias (strcmp, strcoll)
libc_hidden_def (strcoll)
#endif
|
