75 lines
1.9 KiB
ArmAsm
75 lines
1.9 KiB
ArmAsm
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/*
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* Copyright (c) 2020, Arm Limited. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <asm_macros.S>
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.syntax unified
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.global memset
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/* -----------------------------------------------------------------------
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* void *memset(void *dst, int val, size_t count)
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*
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* Copy the value of 'val' (converted to an unsigned char) into
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* each of the first 'count' characters of the object pointed to by 'dst'.
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*
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* Returns the value of 'dst'.
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* -----------------------------------------------------------------------
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*/
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func memset
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mov r12, r0 /* keep r0 */
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tst r0, #3
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beq aligned /* 4-bytes aligned */
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/* Unaligned 'dst' */
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unaligned:
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subs r2, r2, #1
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strbhs r1, [r12], #1
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bxls lr /* return if 0 */
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tst r12, #3
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bne unaligned /* continue while unaligned */
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/* 4-bytes aligned */
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aligned:bfi r1, r1, #8, #8 /* propagate 'val' */
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bfi r1, r1, #16, #16
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mov r3, r1
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cmp r2, #16
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blo less_16 /* < 16 */
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push {r4, lr}
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mov r4, r1
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mov lr, r1
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write_32:
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subs r2, r2, #32
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stmiahs r12!, {r1, r3, r4, lr}
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stmiahs r12!, {r1, r3, r4, lr}
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bhi write_32 /* write 32 bytes in a loop */
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popeq {r4, pc} /* return if 0 */
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lsls r2, r2, #28 /* C = r2[4]; N = r2[3]; Z = r2[3:0] */
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stmiacs r12!, {r1, r3, r4, lr} /* write 16 bytes */
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popeq {r4, pc} /* return if 16 */
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stmiami r12!, {r1, r3} /* write 8 bytes */
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lsls r2, r2, #2 /* C = r2[2]; N = r2[1]; Z = r2[1:0] */
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strcs r1, [r12], #4 /* write 4 bytes */
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popeq {r4, pc} /* return if 8 or 4 */
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strhmi r1, [r12], #2 /* write 2 bytes */
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lsls r2, r2, #1 /* N = Z = r2[0] */
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strbmi r1, [r12] /* write 1 byte */
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pop {r4, pc}
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less_16:lsls r2, r2, #29 /* C = r2[3]; N = r2[2]; Z = r2[2:0] */
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stmiacs r12!, {r1, r3} /* write 8 bytes */
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bxeq lr /* return if 8 */
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strmi r1, [r12], #4 /* write 4 bytes */
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lsls r2, r2, #2 /* C = r2[1]; N = Z = r2[0] */
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strhcs r1, [r12], #2 /* write 2 bytes */
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strbmi r1, [r12] /* write 1 byte */
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bx lr
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endfunc memset
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