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