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freebsd
GitHub Repository: freebsd/freebsd-src
 Path: blob/main/lib/libc/amd64/string/memset.S
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/*-

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 * Copyright (c) 2018 The FreeBSD Foundation

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 *

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 * This software was developed by Mateusz Guzik <[email protected]>

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 * under sponsorship from the FreeBSD Foundation.

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 *

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 * Redistribution and use in source and binary forms, with or without

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 * modification, are permitted provided that the following conditions

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 * are met:

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 * 1. Redistributions of source code must retain the above copyright

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 *    notice, this list of conditions and the following disclaimer.

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 * 2. Redistributions in binary form must reproduce the above copyright

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 *    notice, this list of conditions and the following disclaimer in the

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 *    documentation and/or other materials provided with the distribution.

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 *

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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND

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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

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 * SUCH DAMAGE.

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 */

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#include <machine/asm.h>

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/*

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 * Note: this routine was written with kernel use in mind (read: no simd),

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 * it is only present in userspace as a temporary measure until something

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 * better gets imported.

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 */

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#define ALIGN_TEXT      .p2align 4,0x90 /* 16-byte alignment, nop filled */

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.macro MEMSET erms

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	movq	%rdi,%rax

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	movq	%rdx,%rcx

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	movzbq	%sil,%r8

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	movabs	$0x0101010101010101,%r10

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	imulq	%r8,%r10

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	cmpq	$32,%rcx

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	jbe	101632f

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	cmpq	$256,%rcx

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	ja	1256f

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	ALIGN_TEXT

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103200:

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	movq	%r10,(%rdi)

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	movq	%r10,8(%rdi)

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	movq	%r10,16(%rdi)

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	movq	%r10,24(%rdi)

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	leaq	32(%rdi),%rdi

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	subq	$32,%rcx

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	cmpq	$32,%rcx

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	ja	103200b

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	cmpb	$16,%cl

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	ja	201632f

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	movq	%r10,-16(%rdi,%rcx)

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	movq	%r10,-8(%rdi,%rcx)

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	ret

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	ALIGN_TEXT

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101632:

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	cmpb	$16,%cl

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	jl	100816f

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201632:

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	movq	%r10,(%rdi)

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	movq	%r10,8(%rdi)

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	movq	%r10,-16(%rdi,%rcx)

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	movq	%r10,-8(%rdi,%rcx)

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	ret

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	ALIGN_TEXT

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100816:

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	cmpb	$8,%cl

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	jl	100408f

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	movq	%r10,(%rdi)

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	movq	%r10,-8(%rdi,%rcx)

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	ret

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	ALIGN_TEXT

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100408:

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	cmpb	$4,%cl

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	jl	100204f

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	movl	%r10d,(%rdi)

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	movl	%r10d,-4(%rdi,%rcx)

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	ret

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	ALIGN_TEXT

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100204:

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	cmpb	$2,%cl

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	jl	100001f

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	movw	%r10w,(%rdi)

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	movw	%r10w,-2(%rdi,%rcx)

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	ret

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	ALIGN_TEXT

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100001:

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	cmpb	$0,%cl

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	je	100000f

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	movb	%r10b,(%rdi)

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100000:

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	ret

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	ALIGN_TEXT

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1256:

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	movq	%rdi,%r9

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	movq	%r10,%rax

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	testl	$15,%edi

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	jnz	3f

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1:

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.if \erms == 1

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	rep

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	stosb

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	movq	%r9,%rax

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.else

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	movq	%rcx,%rdx

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	shrq	$3,%rcx

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	rep

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	stosq

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	movq	%r9,%rax

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	andl	$7,%edx

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	jnz	2f

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	ret

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2:

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	movq	%r10,-8(%rdi,%rdx)

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.endif

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	ret

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	ALIGN_TEXT

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3:

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	movq	%r10,(%rdi)

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	movq	%r10,8(%rdi)

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	movq	%rdi,%r8

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	andq	$15,%r8

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	leaq	-16(%rcx,%r8),%rcx

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	neg	%r8

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	leaq	16(%rdi,%r8),%rdi

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	jmp	1b

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.endm

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ENTRY(memset)

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	MEMSET erms=0

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END(memset)

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	.section .note.GNU-stack,"",%progbits

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