/* strcpy/stpcpy implementation for x86-64.

   Copyright (C) 2002-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Andreas Jaeger <aj@suse.de>, 2002.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

#include "asm-syntax.h"

#ifndef USE_AS_STPCPY

# define STRCPY strcpy

#endif

	.text

ENTRY (STRCPY)

	movq %rsi, %rcx		/* Source register. */

	andl $7, %ecx		/* mask alignment bits */

	movq %rdi, %rdx		/* Duplicate destination pointer.  */

	jz 5f			/* aligned => start loop */

	neg %ecx		/* We need to align to 8 bytes.  */

	addl $8,%ecx

	/* Search the first bytes directly.  */

0:

	movb	(%rsi), %al	/* Fetch a byte */

	testb	%al, %al	/* Is it NUL? */

	movb	%al, (%rdx)	/* Store it */

	jz	4f		/* If it was NUL, done! */

	incq	%rsi

	incq	%rdx

	decl	%ecx

	jnz	0b

5:

	movq $0xfefefefefefefeff,%r8

	/* Now the sources is aligned.  Unfortunatly we cannot force

	   to have both source and destination aligned, so ignore the

	   alignment of the destination.  */

	.p2align 4

1:

	/* 1st unroll.  */

	movq	(%rsi), %rax	/* Read double word (8 bytes).  */

	addq	$8, %rsi	/* Adjust pointer for next word.  */

	movq	%rax, %r9	/* Save a copy for NUL finding.  */

	addq	%r8, %r9	/* add the magic value to the word.  We get

				   carry bits reported for each byte which

				   is *not* 0 */

	jnc	3f		/* highest byte is NUL => return pointer */

	xorq	%rax, %r9	/* (word+magic)^word */

	orq	%r8, %r9	/* set all non-carry bits */

	incq	%r9		/* add 1: if one carry bit was *not* set

				   the addition will not result in 0.  */

	jnz	3f		/* found NUL => return pointer */

	movq	%rax, (%rdx)	/* Write value to destination.  */

	addq	$8, %rdx	/* Adjust pointer.  */

	/* 2nd unroll.  */

	movq	(%rsi), %rax	/* Read double word (8 bytes).  */

	addq	$8, %rsi	/* Adjust pointer for next word.  */

	movq	%rax, %r9	/* Save a copy for NUL finding.  */

	addq	%r8, %r9	/* add the magic value to the word.  We get

				   carry bits reported for each byte which

				   is *not* 0 */

	jnc	3f		/* highest byte is NUL => return pointer */

	xorq	%rax, %r9	/* (word+magic)^word */

	orq	%r8, %r9	/* set all non-carry bits */

	incq	%r9		/* add 1: if one carry bit was *not* set

				   the addition will not result in 0.  */

	jnz	3f		/* found NUL => return pointer */

	movq	%rax, (%rdx)	/* Write value to destination.  */

	addq	$8, %rdx	/* Adjust pointer.  */

	/* 3rd unroll.  */

	movq	(%rsi), %rax	/* Read double word (8 bytes).  */

	addq	$8, %rsi	/* Adjust pointer for next word.  */

	movq	%rax, %r9	/* Save a copy for NUL finding.  */

	addq	%r8, %r9	/* add the magic value to the word.  We get

				   carry bits reported for each byte which

				   is *not* 0 */

	jnc	3f		/* highest byte is NUL => return pointer */

	xorq	%rax, %r9	/* (word+magic)^word */

	orq	%r8, %r9	/* set all non-carry bits */

	incq	%r9		/* add 1: if one carry bit was *not* set

				   the addition will not result in 0.  */

	jnz	3f		/* found NUL => return pointer */

	movq	%rax, (%rdx)	/* Write value to destination.  */

	addq	$8, %rdx	/* Adjust pointer.  */

	/* 4th unroll.  */

	movq	(%rsi), %rax	/* Read double word (8 bytes).  */

	addq	$8, %rsi	/* Adjust pointer for next word.  */

	movq	%rax, %r9	/* Save a copy for NUL finding.  */

	addq	%r8, %r9	/* add the magic value to the word.  We get

				   carry bits reported for each byte which

				   is *not* 0 */

	jnc	3f		/* highest byte is NUL => return pointer */

	xorq	%rax, %r9	/* (word+magic)^word */

	orq	%r8, %r9	/* set all non-carry bits */

	incq	%r9		/* add 1: if one carry bit was *not* set

				   the addition will not result in 0.  */

	jnz	3f		/* found NUL => return pointer */

	movq	%rax, (%rdx)	/* Write value to destination.  */

	addq	$8, %rdx	/* Adjust pointer.  */

	jmp	1b		/* Next iteration.  */

	/* Do the last few bytes. %rax contains the value to write.

	   The loop is unrolled twice.  */

	.p2align 4

3:

	/* Note that stpcpy needs to return with the value of the NUL

	   byte.  */

	movb	%al, (%rdx)	/* 1st byte.  */

	testb	%al, %al	/* Is it NUL.  */

	jz	4f		/* yes, finish.  */

	incq	%rdx		/* Increment destination.  */

	movb	%ah, (%rdx)	/* 2nd byte.  */

	testb	%ah, %ah	/* Is it NUL?.  */

	jz	4f		/* yes, finish.  */

	incq	%rdx		/* Increment destination.  */

	shrq	$16, %rax	/* Shift...  */

	jmp	3b		/* and look at next two bytes in %rax.  */

4:

#ifdef USE_AS_STPCPY

	movq	%rdx, %rax	/* Destination is return value.  */

#else

	movq	%rdi, %rax	/* Source is return value.  */

#endif

	retq

END (STRCPY)

#ifndef USE_AS_STPCPY

libc_hidden_builtin_def (strcpy)

#endif