#ifndef __ASM_ARM_UNALIGNED_H #define __ASM_ARM_UNALIGNED_H #include extern int __bug_unaligned_x(void *ptr); /* * What is the most efficient way of loading/storing an unaligned value? * * That is the subject of this file. Efficiency here is defined as * minimum code size with minimum register usage for the common cases. * It is currently not believed that long longs are common, so we * trade efficiency for the chars, shorts and longs against the long * longs. * * Current stats with gcc 2.7.2.2 for these functions: * * ptrsize get: code regs put: code regs * 1 1 1 1 2 * 2 3 2 3 2 * 4 7 3 7 3 * 8 20 6 16 6 * * gcc 2.95.1 seems to code differently: * * ptrsize get: code regs put: code regs * 1 1 1 1 2 * 2 3 2 3 2 * 4 7 4 7 4 * 8 19 8 15 6 * * which may or may not be more efficient (depending upon whether * you can afford the extra registers). Hopefully the gcc 2.95 * is inteligent enough to decide if it is better to use the * extra register, but evidence so far seems to suggest otherwise. * * Unfortunately, gcc is not able to optimise the high word * out of long long >> 32, or the low word from long long << 32 */ #define __get_unaligned_2(__p) \ (__p[0] | __p[1] << 8) #define __get_unaligned_4(__p) \ (__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24) #define get_unaligned(ptr) \ ({ \ __typeof__(*(ptr)) __v; \ __u8 *__p = (__u8 *)(ptr); \ switch (sizeof(*(ptr))) { \ case 1: __v = *(ptr); break; \ case 2: __v = __get_unaligned_2(__p); break; \ case 4: __v = __get_unaligned_4(__p); break; \ case 8: { \ unsigned int __v1, __v2; \ __v2 = __get_unaligned_4((__p+4)); \ __v1 = __get_unaligned_4(__p); \ __v = ((unsigned long long)__v2 << 32 | __v1); \ } \ break; \ default: __v = __bug_unaligned_x(__p); break; \ } \ __v; \ }) static inline void __put_unaligned_2(__u32 __v, register __u8 *__p) { *__p++ = __v; *__p++ = __v >> 8; } static inline void __put_unaligned_4(__u32 __v, register __u8 *__p) { __put_unaligned_2(__v >> 16, __p + 2); __put_unaligned_2(__v, __p); } static inline void __put_unaligned_8(const unsigned long long __v, register __u8 *__p) { /* * tradeoff: 8 bytes of stack for all unaligned puts (2 * instructions), or an extra register in the long long * case - go for the extra register. */ __put_unaligned_4(__v >> 32, __p+4); __put_unaligned_4(__v, __p); } /* * Try to store an unaligned value as efficiently as possible. */ #define put_unaligned(val,ptr) \ ({ \ switch (sizeof(*(ptr))) { \ case 1: \ *(ptr) = (val); \ break; \ case 2: __put_unaligned_2((val),(__u8 *)(ptr)); \ break; \ case 4: __put_unaligned_4((val),(__u8 *)(ptr)); \ break; \ case 8: __put_unaligned_8((val),(__u8 *)(ptr)); \ break; \ default: __bug_unaligned_x(ptr); \ break; \ } \ (void) 0; \ }) #endif