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
20 static 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
36 static 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
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