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 
__arch_swab32(__u32 x)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 
__arch_swab16(__u16 x)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