FreeCalypso > hg > freecalypso-tools
diff target-utils/libc/bzero.S @ 88:4f3843165014
target-utils/libc: bzero imported from Citrine
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 28 Oct 2016 22:22:56 +0000 |
parents | |
children | bfed7a5c21a6 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/target-utils/libc/bzero.S Fri Oct 28 22:22:56 2016 +0000 @@ -0,0 +1,56 @@ +/* + * 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 + strge r2, [r0], #4 + bgt 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