nuttx/libs/libc/machine/arm/armv7-r/gnu/arch_memset.S

/****************************************************************************
 * libs/libc/machine/arm/armv7-r/gnu/arch_memset.S
 *
 * Copyright (C) 2013 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 ****************************************************************************/

#include "libc.h"

#ifdef LIBC_BUILD_MEMSET

	.arm
	.syntax unified
	.global memset
	.type	memset, %function
memset:
	mov         r3, r0
	// At this point only d0, d1 are going to be used below.
	vdup.8      q0, r1
	cmp         r2, #16
	blo         .L_set_less_than_16_unknown_align

.L_check_alignment:
	// Align destination to a double word to avoid the store crossing
	// a cache line boundary.
	ands        ip, r3, #7
	bne         .L_do_double_word_align

.L_double_word_aligned:
	// Duplicate since the less than 64 can use d2, d3.
	vmov        q1, q0
	subs        r2, #64
	blo         .L_set_less_than_64

	// Duplicate the copy value so that we can store 64 bytes at a time.
	vmov        q2, q0
	vmov        q3, q0

1:
	// Main loop stores 64 bytes at a time.
	subs        r2, #64
	vstmia      r3!, {d0 - d7}
	bge         1b

.L_set_less_than_64:
	// Restore r2 to the count of bytes left to set.
	add         r2, #64
	lsls        ip, r2, #27
	bcc         .L_set_less_than_32
	// Set 32 bytes.
	vstmia      r3!, {d0 - d3}

.L_set_less_than_32:
	bpl         .L_set_less_than_16
	// Set 16 bytes.
	vstmia      r3!, {d0, d1}

.L_set_less_than_16:
	// Less than 16 bytes to set.
	lsls        ip, r2, #29
	bcc         .L_set_less_than_8

	// Set 8 bytes.
	vstmia      r3!, {d0}

.L_set_less_than_8:
	bpl         .L_set_less_than_4
	// Set 4 bytes
	vst1.32     {d0[0]}, [r3]!

.L_set_less_than_4:
	lsls        ip, r2, #31
	it          ne
	strbne      r1, [r3], #1
	itt         cs
	strbcs      r1, [r3], #1
	strbcs      r1, [r3]
	bx          lr

.L_do_double_word_align:
	rsb         ip, ip, #8
	sub         r2, r2, ip

	// Do this comparison now, otherwise we'll need to save a
	// register to the stack since we've used all available
	// registers.
	cmp         ip, #4
	blo         1f

	// Need to do a four byte copy.
	movs        ip, ip, lsl #31
	it          mi
	strbmi      r1, [r3], #1
	itt         cs
	strbcs      r1, [r3], #1
	strbcs      r1, [r3], #1
	vst1.32     {d0[0]}, [r3]!
	b           .L_double_word_aligned

1:
	// No four byte copy.
	movs        ip, ip, lsl #31
	it          mi
	strbmi      r1, [r3], #1
	itt         cs
	strbcs      r1, [r3], #1
	strbcs      r1, [r3], #1
	b           .L_double_word_aligned

.L_set_less_than_16_unknown_align:
	// Set up to 15 bytes.
	movs        ip, r2, lsl #29
	bcc         1f
	vst1.8      {d0}, [r3]!
1:
	bge         2f
	vst1.32     {d0[0]}, [r3]!
2:
	movs        ip, r2, lsl #31
	it          mi
	strbmi      r1, [r3], #1
	itt         cs
	strbcs      r1, [r3], #1
	strbcs      r1, [r3], #1
	bx          lr
	.size memset, . - memset

#endif