FreeCalypso > hg > freecalypso-tools
annotate target-utils/libc/bzero.S @ 211:3b009a0a1873
README: minor updates
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 19 May 2017 00:31:54 +0000 |
parents | bfed7a5c21a6 |
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target-utils/libc: bzero imported from Citrine
Mychaela Falconia <falcon@freecalypso.org>
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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 |
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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 |
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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 |
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19 * mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we |
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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 |
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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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target-utils/libc/bzero.S: changed signed conditions to unsigned
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42 strcs r2, [r0], #4 |
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43 bhi 3b @ 1 |
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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 |