annotate target-utils/libc/bzero.S @ 619:f82551c77e58

libserial-newlnx: ASYNC_LOW_LATENCY patch reverted Reports from Das Signal indicate that loadtools performance on Debian is about the same as on Slackware, and that including or omitting the ASYNC_LOW_LATENCY patch from Serg makes no difference. Because the patch in question does not appear to be necessary, it is being reverted until and unless someone other than Serg reports an actual real-world system on which loadtools operation times are slowed compared to the Mother's Slackware reference and on which Slackware-like performance can be restored by setting the ASYNC_LOW_LATENCY flag.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 27 Feb 2020 01:09:48 +0000
parents bfed7a5c21a6
children
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4f3843165014 target-utils/libc: bzero imported from Citrine
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1 /*
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2 * This ARM implementation of bzero() has been derived from:
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3 *
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4 * linux/arch/arm/lib/memzero.S
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5 *
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6 * Copyright (C) 1995-2000 Russell King
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7 *
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8 * This program is free software; you can redistribute it and/or modify
4f3843165014 target-utils/libc: bzero imported from Citrine
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9 * it under the terms of the GNU General Public License version 2 as
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10 * published by the Free Software Foundation.
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11 */
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12
4f3843165014 target-utils/libc: bzero imported from Citrine
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13 .text
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14 .code 32
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15 .globl bzero
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16
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17 /*
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18 * Align the pointer in r0. r3 contains the number of bytes that we are
4f3843165014 target-utils/libc: bzero imported from Citrine
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19 * mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we
4f3843165014 target-utils/libc: bzero imported from Citrine
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20 * don't bother; we use byte stores instead.
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21 */
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22 1: subs r1, r1, #4 @ 1 do we have enough
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23 blt 5f @ 1 bytes to align with?
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24 cmp r3, #2 @ 1
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25 strltb r2, [r0], #1 @ 1
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26 strleb r2, [r0], #1 @ 1
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27 strb r2, [r0], #1 @ 1
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28 add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3))
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29 /*
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30 * The pointer is now aligned and the length is adjusted. Try doing the
4f3843165014 target-utils/libc: bzero imported from Citrine
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31 * bzero again.
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32 */
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33
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34 bzero:
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35 mov r2, #0 @ 1
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36 ands r3, r0, #3 @ 1 unaligned?
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37 bne 1b @ 1
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38 /*
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39 * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
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40 */
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41 3: subs r1, r1, #4
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42 strcs r2, [r0], #4
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43 bhi 3b @ 1
88
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44 bxeq lr @ 1/2 quick exit
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45 /*
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46 * No need to correct the count; we're only testing bits from now on
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47 *
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48 * When we get here, we've got less than 4 bytes to zero. We
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49 * may have an unaligned pointer as well.
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50 */
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51 5: tst r1, #2 @ 1 2 bytes or more?
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52 strneb r2, [r0], #1 @ 1
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53 strneb r2, [r0], #1 @ 1
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54 tst r1, #1 @ 1 a byte left over
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55 strneb r2, [r0], #1 @ 1
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56 bx lr @ 1