1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
2/*
3 * include/asm-xtensa/swab.h
4 *
5 * This file is subject to the terms and conditions of the GNU General Public
6 * License.  See the file "COPYING" in the main directory of this archive
7 * for more details.
8 *
9 * Copyright (C) 2001 - 2005 Tensilica Inc.
10 */
11
12#ifndef _XTENSA_SWAB_H
13#define _XTENSA_SWAB_H
14
15#include <linux/types.h>
16#include <linux/compiler.h>
17
18#define __SWAB_64_THRU_32__
19
20static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
21{
22    __u32 res;
23    /* instruction sequence from Xtensa ISA release 2/2000 */
24    __asm__("ssai     8           \n\t"
25	    "srli     %0, %1, 16  \n\t"
26	    "src      %0, %0, %1  \n\t"
27	    "src      %0, %0, %0  \n\t"
28	    "src      %0, %1, %0  \n"
29	    : "=&a" (res)
30	    : "a" (x)
31	    );
32    return res;
33}
34#define __arch_swab32 __arch_swab32
35
36static inline __attribute_const__ __u16 __arch_swab16(__u16 x)
37{
38    /* Given that 'short' values are signed (i.e., can be negative),
39     * we cannot assume that the upper 16-bits of the register are
40     * zero.  We are careful to mask values after shifting.
41     */
42
43    /* There exists an anomaly between xt-gcc and xt-xcc.  xt-gcc
44     * inserts an extui instruction after putting this function inline
45     * to ensure that it uses only the least-significant 16 bits of
46     * the result.  xt-xcc doesn't use an extui, but assumes the
47     * __asm__ macro follows convention that the upper 16 bits of an
48     * 'unsigned short' result are still zero.  This macro doesn't
49     * follow convention; indeed, it leaves garbage in the upport 16
50     * bits of the register.
51
52     * Declaring the temporary variables 'res' and 'tmp' to be 32-bit
53     * types while the return type of the function is a 16-bit type
54     * forces both compilers to insert exactly one extui instruction
55     * (or equivalent) to mask off the upper 16 bits. */
56
57    __u32 res;
58    __u32 tmp;
59
60    __asm__("extui    %1, %2, 8, 8\n\t"
61	    "slli     %0, %2, 8   \n\t"
62	    "or       %0, %0, %1  \n"
63	    : "=&a" (res), "=&a" (tmp)
64	    : "a" (x)
65	    );
66
67    return res;
68}
69#define __arch_swab16 __arch_swab16
70
71#endif /* _XTENSA_SWAB_H */
72