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/* Copyright (c) 2012, 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.
*/
/* Assumptions:
*
* ARMv8-a, AArch64
* Unaligned accesses
*
*/
#include <private/bionic_asm.h>
/* By default we assume that the DC instruction can be used to zero
data blocks more efficiently. In some circumstances this might be
unsafe, for example in an asymmetric multiprocessor environment with
different DC clear lengths (neither the upper nor lower lengths are
safe to use).
If code may be run in a virtualized environment, then define
MAYBE_VIRT. This will cause the code to cache the system register
values rather than re-reading them each call. */
#define dstin x0
#define count x2
#define val w1
#define tmp1 x3
#define tmp1w w3
#define tmp2 x4
#define tmp2w w4
#define zva_len_x x5
#define zva_len w5
#define zva_bits_x x6
#define A_l x7
#define A_lw w7
#define dst x8
#define tmp3w w9
ENTRY(memset)
mov dst, dstin /* Preserve return value. */
ands A_lw, val, #255
b.eq .Lzero_mem
orr A_lw, A_lw, A_lw, lsl #8
orr A_lw, A_lw, A_lw, lsl #16
orr A_l, A_l, A_l, lsl #32
.Ltail_maybe_long:
cmp count, #64
b.ge .Lnot_short
.Ltail_maybe_tiny:
cmp count, #15
b.le .Ltail15tiny
.Ltail63:
ands tmp1, count, #0x30
b.eq .Ltail15
add dst, dst, tmp1
cmp tmp1w, #0x20
b.eq 1f
b.lt 2f
stp A_l, A_l, [dst, #-48]
1:
stp A_l, A_l, [dst, #-32]
2:
stp A_l, A_l, [dst, #-16]
.Ltail15:
and count, count, #15
add dst, dst, count
stp A_l, A_l, [dst, #-16] /* Repeat some/all of last store. */
ret
.Ltail15tiny:
/* Set up to 15 bytes. Does not assume earlier memory
being set. */
tbz count, #3, 1f
str A_l, [dst], #8
1:
tbz count, #2, 1f
str A_lw, [dst], #4
1:
tbz count, #1, 1f
strh A_lw, [dst], #2
1:
tbz count, #0, 1f
strb A_lw, [dst]
1:
ret
/* Critical loop. Start at a new cache line boundary. Assuming
* 64 bytes per line, this ensures the entire loop is in one line. */
.p2align 6
.Lnot_short:
neg tmp2, dst
ands tmp2, tmp2, #15
b.eq 2f
/* Bring DST to 128-bit (16-byte) alignment. We know that there's
* more than that to set, so we simply store 16 bytes and advance by
* the amount required to reach alignment. */
sub count, count, tmp2
stp A_l, A_l, [dst]
add dst, dst, tmp2
/* There may be less than 63 bytes to go now. */
cmp count, #63
b.le .Ltail63
2:
sub dst, dst, #16 /* Pre-bias. */
sub count, count, #64
1:
stp A_l, A_l, [dst, #16]
stp A_l, A_l, [dst, #32]
stp A_l, A_l, [dst, #48]
stp A_l, A_l, [dst, #64]!
subs count, count, #64
b.ge 1b
tst count, #0x3f
add dst, dst, #16
b.ne .Ltail63
ret
/* For zeroing memory, check to see if we can use the ZVA feature to
* zero entire 'cache' lines. */
.Lzero_mem:
mov A_l, #0
cmp count, #63
b.le .Ltail_maybe_tiny
neg tmp2, dst
ands tmp2, tmp2, #15
b.eq 1f
sub count, count, tmp2
stp A_l, A_l, [dst]
add dst, dst, tmp2
cmp count, #63
b.le .Ltail63
1:
/* For zeroing small amounts of memory, it's not worth setting up
* the line-clear code. */
cmp count, #128
b.lt .Lnot_short
#ifdef MAYBE_VIRT
/* For efficiency when virtualized, we cache the ZVA capability. */
adrp tmp2, .Lcache_clear
ldr zva_len, [tmp2, #:lo12:.Lcache_clear]
tbnz zva_len, #31, .Lnot_short
cbnz zva_len, .Lzero_by_line
mrs tmp1, dczid_el0
tbz tmp1, #4, 1f
/* ZVA not available. Remember this for next time. */
mov zva_len, #~0
str zva_len, [tmp2, #:lo12:.Lcache_clear]
b .Lnot_short
1:
mov tmp3w, #4
and zva_len, tmp1w, #15 /* Safety: other bits reserved. */
lsl zva_len, tmp3w, zva_len
str zva_len, [tmp2, #:lo12:.Lcache_clear]
#else
mrs tmp1, dczid_el0
tbnz tmp1, #4, .Lnot_short
mov tmp3w, #4
and zva_len, tmp1w, #15 /* Safety: other bits reserved. */
lsl zva_len, tmp3w, zva_len
#endif
.Lzero_by_line:
/* Compute how far we need to go to become suitably aligned. We're
* already at quad-word alignment. */
cmp count, zva_len_x
b.lt .Lnot_short /* Not enough to reach alignment. */
sub zva_bits_x, zva_len_x, #1
neg tmp2, dst
ands tmp2, tmp2, zva_bits_x
b.eq 1f /* Already aligned. */
/* Not aligned, check that there's enough to copy after alignment. */
sub tmp1, count, tmp2
cmp tmp1, #64
ccmp tmp1, zva_len_x, #8, ge /* NZCV=0b1000 */
b.lt .Lnot_short
/* We know that there's at least 64 bytes to zero and that it's safe
* to overrun by 64 bytes. */
mov count, tmp1
2:
stp A_l, A_l, [dst]
stp A_l, A_l, [dst, #16]
stp A_l, A_l, [dst, #32]
subs tmp2, tmp2, #64
stp A_l, A_l, [dst, #48]
add dst, dst, #64
b.ge 2b
/* We've overrun a bit, so adjust dst downwards. */
add dst, dst, tmp2
1:
sub count, count, zva_len_x
3:
dc zva, dst
add dst, dst, zva_len_x
subs count, count, zva_len_x
b.ge 3b
ands count, count, zva_bits_x
b.ne .Ltail_maybe_long
ret
END(memset)
#ifdef MAYBE_VIRT
.bss
.p2align 2
.Lcache_clear:
.space 4
#endif
|
