167 lines
4.8 KiB
ArmAsm
167 lines
4.8 KiB
ArmAsm
/* memcmp - compare memory
|
|
|
|
Copyright (c) 2013, Linaro Limited
|
|
All rights reserved.
|
|
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, are permitted provided that the following conditions are met:
|
|
* Redistributions of source code must retain the above copyright
|
|
notice, this list of conditions and the following disclaimer.
|
|
* Redistributions in binary form must reproduce the above copyright
|
|
notice, this list of conditions and the following disclaimer in the
|
|
documentation and/or other materials provided with the distribution.
|
|
* Neither the name of the Linaro nor the
|
|
names of its contributors may be used to endorse or promote products
|
|
derived from this software without specific prior written permission.
|
|
|
|
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
|
|
|
|
#if (defined (__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED))
|
|
/* See memcmp-stub.c */
|
|
#else
|
|
/* Assumptions:
|
|
*
|
|
* ARMv8-a, AArch64
|
|
*/
|
|
|
|
.macro def_fn f p2align=0
|
|
.text
|
|
.p2align \p2align
|
|
.global \f
|
|
.type \f, %function
|
|
\f:
|
|
.endm
|
|
|
|
/* Parameters and result. */
|
|
#define src1 x0
|
|
#define src2 x1
|
|
#define limit x2
|
|
#define result x0
|
|
|
|
/* Internal variables. */
|
|
#define data1 x3
|
|
#define data1w w3
|
|
#define data2 x4
|
|
#define data2w w4
|
|
#define has_nul x5
|
|
#define diff x6
|
|
#define endloop x7
|
|
#define tmp1 x8
|
|
#define tmp2 x9
|
|
#define tmp3 x10
|
|
#define pos x11
|
|
#define limit_wd x12
|
|
#define mask x13
|
|
|
|
def_fn memcmp p2align=6
|
|
cbz limit, .Lret0
|
|
eor tmp1, src1, src2
|
|
tst tmp1, #7
|
|
b.ne .Lmisaligned8
|
|
ands tmp1, src1, #7
|
|
b.ne .Lmutual_align
|
|
add limit_wd, limit, #7
|
|
lsr limit_wd, limit_wd, #3
|
|
/* Start of performance-critical section -- one 64B cache line. */
|
|
.Lloop_aligned:
|
|
ldr data1, [src1], #8
|
|
ldr data2, [src2], #8
|
|
.Lstart_realigned:
|
|
subs limit_wd, limit_wd, #1
|
|
eor diff, data1, data2 /* Non-zero if differences found. */
|
|
csinv endloop, diff, xzr, ne /* Last Dword or differences. */
|
|
cbz endloop, .Lloop_aligned
|
|
/* End of performance-critical section -- one 64B cache line. */
|
|
|
|
/* Not reached the limit, must have found a diff. */
|
|
cbnz limit_wd, .Lnot_limit
|
|
|
|
/* Limit % 8 == 0 => all bytes significant. */
|
|
ands limit, limit, #7
|
|
b.eq .Lnot_limit
|
|
|
|
lsl limit, limit, #3 /* Bits -> bytes. */
|
|
mov mask, #~0
|
|
#ifdef __AARCH64EB__
|
|
lsr mask, mask, limit
|
|
#else
|
|
lsl mask, mask, limit
|
|
#endif
|
|
bic data1, data1, mask
|
|
bic data2, data2, mask
|
|
|
|
orr diff, diff, mask
|
|
.Lnot_limit:
|
|
|
|
#ifndef __AARCH64EB__
|
|
rev diff, diff
|
|
rev data1, data1
|
|
rev data2, data2
|
|
#endif
|
|
/* The MS-non-zero bit of DIFF marks either the first bit
|
|
that is different, or the end of the significant data.
|
|
Shifting left now will bring the critical information into the
|
|
top bits. */
|
|
clz pos, diff
|
|
lsl data1, data1, pos
|
|
lsl data2, data2, pos
|
|
/* But we need to zero-extend (char is unsigned) the value and then
|
|
perform a signed 32-bit subtraction. */
|
|
lsr data1, data1, #56
|
|
sub result, data1, data2, lsr #56
|
|
ret
|
|
|
|
.Lmutual_align:
|
|
/* Sources are mutually aligned, but are not currently at an
|
|
alignment boundary. Round down the addresses and then mask off
|
|
the bytes that precede the start point. */
|
|
bic src1, src1, #7
|
|
bic src2, src2, #7
|
|
add limit, limit, tmp1 /* Adjust the limit for the extra. */
|
|
lsl tmp1, tmp1, #3 /* Bytes beyond alignment -> bits. */
|
|
ldr data1, [src1], #8
|
|
neg tmp1, tmp1 /* Bits to alignment -64. */
|
|
ldr data2, [src2], #8
|
|
mov tmp2, #~0
|
|
#ifdef __AARCH64EB__
|
|
/* Big-endian. Early bytes are at MSB. */
|
|
lsl tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
|
|
#else
|
|
/* Little-endian. Early bytes are at LSB. */
|
|
lsr tmp2, tmp2, tmp1 /* Shift (tmp1 & 63). */
|
|
#endif
|
|
add limit_wd, limit, #7
|
|
orr data1, data1, tmp2
|
|
orr data2, data2, tmp2
|
|
lsr limit_wd, limit_wd, #3
|
|
b .Lstart_realigned
|
|
|
|
.Lret0:
|
|
mov result, #0
|
|
ret
|
|
|
|
.p2align 6
|
|
.Lmisaligned8:
|
|
sub limit, limit, #1
|
|
1:
|
|
/* Perhaps we can do better than this. */
|
|
ldrb data1w, [src1], #1
|
|
ldrb data2w, [src2], #1
|
|
subs limit, limit, #1
|
|
ccmp data1w, data2w, #0, cs /* NZCV = 0b0000. */
|
|
b.eq 1b
|
|
sub result, data1, data2
|
|
ret
|
|
.size memcmp, . - memcmp
|
|
|
|
#endif |