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fc30b13b25
Typical saving is 15-20 bytes in each file using memmove(). Signed-off-by: Michael Brown <mcb30@ipxe.org>
243 lines
6.6 KiB
C
243 lines
6.6 KiB
C
#ifndef ETHERBOOT_BITS_STRING_H
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#define ETHERBOOT_BITS_STRING_H
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/*
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* Taken from Linux /usr/include/asm/string.h
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* All except memcpy, memmove, memset and memcmp removed.
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*
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* Non-standard memswap() function added because it saves quite a bit
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* of code (mbrown@fensystems.co.uk).
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*/
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/*
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* This string-include defines all string functions as inline
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* functions. Use gcc. It also assumes ds=es=data space, this should be
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* normal. Most of the string-functions are rather heavily hand-optimized,
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* see especially strtok,strstr,str[c]spn. They should work, but are not
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* very easy to understand. Everything is done entirely within the register
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* set, making the functions fast and clean. String instructions have been
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* used through-out, making for "slightly" unclear code :-)
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*
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* NO Copyright (C) 1991, 1992 Linus Torvalds,
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* consider these trivial functions to be PD.
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*/
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FILE_LICENCE ( PUBLIC_DOMAIN );
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#define __HAVE_ARCH_MEMCPY
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extern void * __memcpy ( void *dest, const void *src, size_t len );
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extern void * __memcpy_reverse ( void *dest, const void *src, size_t len );
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static inline __attribute__ (( always_inline )) void *
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__constant_memcpy ( void *dest, const void *src, size_t len ) {
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union {
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uint32_t u32[2];
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uint16_t u16[4];
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uint8_t u8[8];
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} __attribute__ (( __may_alias__ )) *dest_u = dest;
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const union {
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uint32_t u32[2];
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uint16_t u16[4];
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uint8_t u8[8];
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} __attribute__ (( __may_alias__ )) *src_u = src;
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const void *esi;
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void *edi;
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switch ( len ) {
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case 0 : /* 0 bytes */
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return dest;
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/*
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* Single-register moves; these are always better than a
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* string operation. We can clobber an arbitrary two
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* registers (data, source, dest can re-use source register)
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* instead of being restricted to esi and edi. There's also a
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* much greater potential for optimising with nearby code.
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*
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*/
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case 1 : /* 4 bytes */
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dest_u->u8[0] = src_u->u8[0];
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return dest;
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case 2 : /* 6 bytes */
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dest_u->u16[0] = src_u->u16[0];
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return dest;
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case 4 : /* 4 bytes */
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dest_u->u32[0] = src_u->u32[0];
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return dest;
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/*
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* Double-register moves; these are probably still a win.
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*
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*/
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case 3 : /* 12 bytes */
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dest_u->u16[0] = src_u->u16[0];
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dest_u->u8[2] = src_u->u8[2];
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return dest;
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case 5 : /* 10 bytes */
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dest_u->u32[0] = src_u->u32[0];
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dest_u->u8[4] = src_u->u8[4];
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return dest;
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case 6 : /* 12 bytes */
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dest_u->u32[0] = src_u->u32[0];
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dest_u->u16[2] = src_u->u16[2];
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return dest;
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case 8 : /* 10 bytes */
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dest_u->u32[0] = src_u->u32[0];
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dest_u->u32[1] = src_u->u32[1];
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return dest;
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}
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/* Even if we have to load up esi and edi ready for a string
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* operation, we can sometimes save space by using multiple
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* single-byte "movs" operations instead of loading up ecx and
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* using "rep movsb".
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*
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* "load ecx, rep movsb" is 7 bytes, plus an average of 1 byte
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* to allow for saving/restoring ecx 50% of the time.
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*
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* "movsl" and "movsb" are 1 byte each, "movsw" is two bytes.
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* (In 16-bit mode, "movsl" is 2 bytes and "movsw" is 1 byte,
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* but "movsl" moves twice as much data, so it balances out).
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*
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* The cutoff point therefore occurs around 26 bytes; the byte
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* requirements for each method are:
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*
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* len 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
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* #bytes (ecx) 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8
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* #bytes (no ecx) 4 5 6 7 5 6 7 8 6 7 8 9 7 8 9 10
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*/
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esi = src;
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edi = dest;
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if ( len >= 26 )
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return __memcpy ( dest, src, len );
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if ( len >= 6*4 )
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__asm__ __volatile__ ( "movsl" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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if ( len >= 5*4 )
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__asm__ __volatile__ ( "movsl" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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if ( len >= 4*4 )
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__asm__ __volatile__ ( "movsl" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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if ( len >= 3*4 )
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__asm__ __volatile__ ( "movsl" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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if ( len >= 2*4 )
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__asm__ __volatile__ ( "movsl" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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if ( len >= 1*4 )
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__asm__ __volatile__ ( "movsl" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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if ( ( len % 4 ) >= 2 )
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__asm__ __volatile__ ( "movsw" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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if ( ( len % 2 ) >= 1 )
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__asm__ __volatile__ ( "movsb" : "=&D" ( edi ), "=&S" ( esi )
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: "0" ( edi ), "1" ( esi ) : "memory" );
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return dest;
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}
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#define memcpy( dest, src, len ) \
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( __builtin_constant_p ( (len) ) ? \
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__constant_memcpy ( (dest), (src), (len) ) : \
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__memcpy ( (dest), (src), (len) ) )
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#define __HAVE_ARCH_MEMMOVE
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extern void * __memmove ( void *dest, const void *src, size_t len );
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/**
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* Copy (possibly overlapping) memory area
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*
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* @v dest Destination address
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* @v src Source address
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* @v len Length
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* @ret dest Destination address
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*/
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static inline __attribute__ (( always_inline )) void *
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memmove ( void *dest, const void *src, size_t len ) {
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ssize_t offset = ( dest - src );
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if ( __builtin_constant_p ( offset ) ) {
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if ( offset <= 0 ) {
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return memcpy ( dest, src, len );
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} else {
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return __memcpy_reverse ( dest, src, len );
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}
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} else {
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return __memmove ( dest, src, len );
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}
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}
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#define __HAVE_ARCH_MEMSET
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static inline void * memset(void *s, int c,size_t count)
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{
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int d0, d1;
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__asm__ __volatile__(
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"cld\n\t"
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"rep\n\t"
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"stosb"
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: "=&c" (d0), "=&D" (d1)
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:"a" (c),"1" (s),"0" (count)
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:"memory");
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return s;
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}
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#define __HAVE_ARCH_MEMSWAP
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static inline void * memswap(void *dest, void *src, size_t n)
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{
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long d0, d1, d2, d3;
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__asm__ __volatile__(
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"\n1:\t"
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"movb (%2),%%al\n\t"
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"xchgb (%1),%%al\n\t"
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"inc %1\n\t"
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"stosb\n\t"
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"loop 1b"
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: "=&c" (d0), "=&S" (d1), "=&D" (d2), "=&a" (d3)
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: "0" (n), "1" (src), "2" (dest)
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: "memory" );
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return dest;
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}
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#define __HAVE_ARCH_STRNCMP
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static inline int strncmp(const char * cs,const char * ct,size_t count)
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{
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register int __res;
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int d0, d1, d2;
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__asm__ __volatile__(
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"1:\tdecl %3\n\t"
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"js 2f\n\t"
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"lodsb\n\t"
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"scasb\n\t"
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"jne 3f\n\t"
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"testb %%al,%%al\n\t"
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"jne 1b\n"
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"2:\txorl %%eax,%%eax\n\t"
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"jmp 4f\n"
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"3:\tsbbl %%eax,%%eax\n\t"
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"orb $1,%%al\n"
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"4:"
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:"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2)
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:"1" (cs),"2" (ct),"3" (count));
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return __res;
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}
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#define __HAVE_ARCH_STRLEN
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static inline size_t strlen(const char * s)
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{
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int d0;
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register int __res;
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__asm__ __volatile__(
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"repne\n\t"
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"scasb\n\t"
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"notl %0\n\t"
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"decl %0"
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:"=c" (__res), "=&D" (d0) :"1" (s),"a" (0), "0" (0xffffffff));
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return __res;
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}
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#endif /* ETHERBOOT_BITS_STRING_H */
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