1/* strspn (str, ss) -- Return the length of the initial segment of STR
2			which contains only characters from SS.
3   For AMD x86-64.
4   Copyright (C) 1994-2021 Free Software Foundation, Inc.
5   This file is part of the GNU C Library.
6
7   The GNU C Library is free software; you can redistribute it and/or
8   modify it under the terms of the GNU Lesser General Public
9   License as published by the Free Software Foundation; either
10   version 2.1 of the License, or (at your option) any later version.
11
12   The GNU C Library is distributed in the hope that it will be useful,
13   but WITHOUT ANY WARRANTY; without even the implied warranty of
14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15   Lesser General Public License for more details.
16
17   You should have received a copy of the GNU Lesser General Public
18   License along with the GNU C Library; if not, see
19   <https://www.gnu.org/licenses/>.  */
20
21#include <sysdep.h>
22
23	.text
24ENTRY (strspn)
25
26	movq %rdi, %rdx		/* Save SRC.  */
27
28	/* First we create a table with flags for all possible characters.
29	   For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
30	   supported by the C string functions we have 256 characters.
31	   Before inserting marks for the stop characters we clear the whole
32	   table.  */
33	movq %rdi, %r8			/* Save value.  */
34	subq $256, %rsp			/* Make space for 256 bytes.  */
35	cfi_adjust_cfa_offset(256)
36	movl $32,  %ecx			/* 32*8 bytes = 256 bytes.  */
37	movq %rsp, %rdi
38	xorl %eax, %eax			/* We store 0s.  */
39	cld
40	rep
41	stosq
42
43	movq %rsi, %rax			/* Setup stopset.  */
44
45/* For understanding the following code remember that %rcx == 0 now.
46   Although all the following instruction only modify %cl we always
47   have a correct zero-extended 64-bit value in %rcx.  */
48
49	.p2align 4
50L(2):	movb (%rax), %cl	/* get byte from stopset */
51	testb %cl, %cl		/* is NUL char? */
52	jz L(1)			/* yes => start compare loop */
53	movb %cl, (%rsp,%rcx)	/* set corresponding byte in stopset table */
54
55	movb 1(%rax), %cl	/* get byte from stopset */
56	testb $0xff, %cl	/* is NUL char? */
57	jz L(1)			/* yes => start compare loop */
58	movb %cl, (%rsp,%rcx)	/* set corresponding byte in stopset table */
59
60	movb 2(%rax), %cl	/* get byte from stopset */
61	testb $0xff, %cl	/* is NUL char? */
62	jz L(1)			/* yes => start compare loop */
63	movb %cl, (%rsp,%rcx)	/* set corresponding byte in stopset table */
64
65	movb 3(%rax), %cl	/* get byte from stopset */
66	addq $4, %rax		/* increment stopset pointer */
67	movb %cl, (%rsp,%rcx)	/* set corresponding byte in stopset table */
68	testb $0xff, %cl	/* is NUL char? */
69	jnz L(2)		/* no => process next dword from stopset */
70
71L(1):	leaq -4(%rdx), %rax	/* prepare loop */
72
73	/* We use a neat trick for the following loop.  Normally we would
74	   have to test for two termination conditions
75	   1. a character in the stopset was found
76	   and
77	   2. the end of the string was found
78	   But as a sign that the character is in the stopset we store its
79	   value in the table.  But the value of NUL is NUL so the loop
80	   terminates for NUL in every case.  */
81
82	.p2align 4
83L(3):	addq $4, %rax		/* adjust pointer for full loop round */
84
85	movb (%rax), %cl	/* get byte from string */
86	testb %cl, (%rsp,%rcx)	/* is it contained in skipset? */
87	jz L(4)			/* no => return */
88
89	movb 1(%rax), %cl	/* get byte from string */
90	testb %cl, (%rsp,%rcx)	/* is it contained in skipset? */
91	jz L(5)			/* no => return */
92
93	movb 2(%rax), %cl	/* get byte from string */
94	testb %cl, (%rsp,%rcx)	/* is it contained in skipset? */
95	jz L(6)			/* no => return */
96
97	movb 3(%rax), %cl	/* get byte from string */
98	testb %cl, (%rsp,%rcx)	/* is it contained in skipset? */
99	jnz L(3)		/* yes => start loop again */
100
101	incq %rax		/* adjust pointer */
102L(6):	incq %rax
103L(5):	incq %rax
104
105L(4):	addq $256, %rsp		/* remove stopset */
106	cfi_adjust_cfa_offset(-256)
107	subq %rdx, %rax		/* we have to return the number of valid
108				   characters, so compute distance to first
109				   non-valid character */
110	ret
111END (strspn)
112libc_hidden_builtin_def (strspn)
113