FreeCalypso > hg > freecalypso-tools
view target-utils/libc/bzero.S @ 238:08ad558c1fbc
CHANGES: exitcodes.h addition documented
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sun, 20 Aug 2017 18:40:03 +0000 |
parents | bfed7a5c21a6 |
children |
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/* * This ARM implementation of bzero() has been derived from: * * linux/arch/arm/lib/memzero.S * * Copyright (C) 1995-2000 Russell King * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ .text .code 32 .globl bzero /* * Align the pointer in r0. r3 contains the number of bytes that we are * mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we * don't bother; we use byte stores instead. */ 1: subs r1, r1, #4 @ 1 do we have enough blt 5f @ 1 bytes to align with? cmp r3, #2 @ 1 strltb r2, [r0], #1 @ 1 strleb r2, [r0], #1 @ 1 strb r2, [r0], #1 @ 1 add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3)) /* * The pointer is now aligned and the length is adjusted. Try doing the * bzero again. */ bzero: mov r2, #0 @ 1 ands r3, r0, #3 @ 1 unaligned? bne 1b @ 1 /* * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary. */ 3: subs r1, r1, #4 strcs r2, [r0], #4 bhi 3b @ 1 bxeq lr @ 1/2 quick exit /* * No need to correct the count; we're only testing bits from now on * * When we get here, we've got less than 4 bytes to zero. We * may have an unaligned pointer as well. */ 5: tst r1, #2 @ 1 2 bytes or more? strneb r2, [r0], #1 @ 1 strneb r2, [r0], #1 @ 1 tst r1, #1 @ 1 a byte left over strneb r2, [r0], #1 @ 1 bx lr @ 1