119 lines
3.1 KiB
C
119 lines
3.1 KiB
C
#ifndef __ASM_ARM_UNALIGNED_H
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#define __ASM_ARM_UNALIGNED_H
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#include <asm/types.h>
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extern int __bug_unaligned_x(void *ptr);
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/*
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* What is the most efficient way of loading/storing an unaligned value?
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*
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* That is the subject of this file. Efficiency here is defined as
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* minimum code size with minimum register usage for the common cases.
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* It is currently not believed that long longs are common, so we
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* trade efficiency for the chars, shorts and longs against the long
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* longs.
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*
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* Current stats with gcc 2.7.2.2 for these functions:
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*
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* ptrsize get: code regs put: code regs
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* 1 1 1 1 2
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* 2 3 2 3 2
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* 4 7 3 7 3
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* 8 20 6 16 6
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*
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* gcc 2.95.1 seems to code differently:
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*
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* ptrsize get: code regs put: code regs
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* 1 1 1 1 2
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* 2 3 2 3 2
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* 4 7 4 7 4
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* 8 19 8 15 6
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*
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* which may or may not be more efficient (depending upon whether
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* you can afford the extra registers). Hopefully the gcc 2.95
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* is inteligent enough to decide if it is better to use the
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* extra register, but evidence so far seems to suggest otherwise.
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*
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* Unfortunately, gcc is not able to optimise the high word
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* out of long long >> 32, or the low word from long long << 32
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*/
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#define __get_unaligned_2_le(__p) \
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(__p[0] | __p[1] << 8)
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#define __get_unaligned_4_le(__p) \
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(__p[0] | __p[1] << 8 | __p[2] << 16 | __p[3] << 24)
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#define __get_unaligned_le(ptr) \
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({ \
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__typeof__(*(ptr)) __v; \
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__u8 *__p = (__u8 *)(ptr); \
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switch (sizeof(*(ptr))) { \
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case 1: __v = *(ptr); break; \
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case 2: __v = __get_unaligned_2_le(__p); break; \
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case 4: __v = __get_unaligned_4_le(__p); break; \
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case 8: { \
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unsigned int __v1, __v2; \
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__v2 = __get_unaligned_4_le((__p+4)); \
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__v1 = __get_unaligned_4_le(__p); \
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__v = ((unsigned long long)__v2 << 32 | __v1); \
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} \
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break; \
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default: __v = __bug_unaligned_x(__p); break; \
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} \
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__v; \
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})
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static inline void __put_unaligned_2_le(__u32 __v, register __u8 *__p)
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{
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*__p++ = __v;
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*__p++ = __v >> 8;
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}
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static inline void __put_unaligned_4_le(__u32 __v, register __u8 *__p)
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{
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__put_unaligned_2_le(__v >> 16, __p + 2);
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__put_unaligned_2_le(__v, __p);
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}
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static inline void __put_unaligned_8_le(const unsigned long long __v, register __u8 *__p)
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{
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/*
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* tradeoff: 8 bytes of stack for all unaligned puts (2
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* instructions), or an extra register in the long long
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* case - go for the extra register.
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*/
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__put_unaligned_4_le(__v >> 32, __p+4);
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__put_unaligned_4_le(__v, __p);
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}
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/*
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* Try to store an unaligned value as efficiently as possible.
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*/
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#define __put_unaligned_le(val,ptr) \
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({ \
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switch (sizeof(*(ptr))) { \
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case 1: \
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*(ptr) = (val); \
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break; \
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case 2: __put_unaligned_2_le((val),(__u8 *)(ptr)); \
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break; \
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case 4: __put_unaligned_4_le((val),(__u8 *)(ptr)); \
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break; \
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case 8: __put_unaligned_8_le((val),(__u8 *)(ptr)); \
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break; \
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default: __bug_unaligned_x(ptr); \
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break; \
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} \
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(void) 0; \
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})
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/*
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* Select endianness
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*/
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#define get_unaligned __get_unaligned_le
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#define put_unaligned __put_unaligned_le
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#endif
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