xref: /aosp_15_r20/bionic/libc/arch-arm64/oryon/memset-nt.S (revision 8d67ca893c1523eb926b9080dbe4e2ffd2a27ba1)

/* Copyright (c) 2012, Linaro Limited
   All rights reserved.
   Copyright (c) 2024 Qualcomm Innovation Center, Inc. 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>

#define dstin		x0
#define val		    w1
#define count		x2
#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
#define tmp4        x10
#define SMALL_BUFFER_SIZE    96

ENTRY(__memset_aarch64_nt)
    mov	dst, dstin		/* Preserve return value.  */
    ands	A_lw, val, #255
    b.eq	.Lzero_mem  /* Use DC ZVA instruction if the val = 0 */
    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:
    mov tmp4, #SMALL_BUFFER_SIZE
    cmp count, tmp4, LSL#10
    /* Use non-temporal instruction if count > SMALL_BUFFER_SIZE */
    bgt L(not_short_nt)
    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
.Lnot_short_nt:
    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
    stnp	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:
    stnp	A_l, A_l, [dst, #16]
    stnp	A_l, A_l, [dst, #32]
    stnp	A_l, A_l, [dst, #48]
    stnp	A_l, A_l, [dst, #64]
    add     dst, dst, #64
    subs	count, count, #64
    b.ge	1b
    tst	count, #0x3f
    add	dst, dst, #16
    b.ne	.Ltail63
    ret
.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
    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
.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_aarch64_nt)