diff options
Diffstat (limited to 'qemu/roms/ipxe/src/arch/x86/core/x86_string.c')
| -rw-r--r-- | qemu/roms/ipxe/src/arch/x86/core/x86_string.c | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/qemu/roms/ipxe/src/arch/x86/core/x86_string.c b/qemu/roms/ipxe/src/arch/x86/core/x86_string.c new file mode 100644 index 000000000..d48347c96 --- /dev/null +++ b/qemu/roms/ipxe/src/arch/x86/core/x86_string.c @@ -0,0 +1,190 @@ +/* + * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License as + * published by the Free Software Foundation; either version 2 of the + * License, or any later version. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA + * 02110-1301, USA. + */ + +/** @file + * + * Optimised string operations + * + */ + +FILE_LICENCE ( GPL2_OR_LATER ); + +#include <string.h> + +/** + * Copy memory area + * + * @v dest Destination address + * @v src Source address + * @v len Length + * @ret dest Destination address + */ +void * __attribute__ (( noinline )) __memcpy ( void *dest, const void *src, + size_t len ) { + void *edi = dest; + const void *esi = src; + int discard_ecx; + + /* We often do large dword-aligned and dword-length block + * moves. Using movsl rather than movsb speeds these up by + * around 32%. + */ + __asm__ __volatile__ ( "rep movsl" + : "=&D" ( edi ), "=&S" ( esi ), + "=&c" ( discard_ecx ) + : "0" ( edi ), "1" ( esi ), "2" ( len >> 2 ) + : "memory" ); + __asm__ __volatile__ ( "rep movsb" + : "=&D" ( edi ), "=&S" ( esi ), + "=&c" ( discard_ecx ) + : "0" ( edi ), "1" ( esi ), "2" ( len & 3 ) + : "memory" ); + return dest; +} + +/** + * Copy memory area backwards + * + * @v dest Destination address + * @v src Source address + * @v len Length + * @ret dest Destination address + */ +void * __attribute__ (( noinline )) __memcpy_reverse ( void *dest, + const void *src, + size_t len ) { + void *edi = ( dest + len - 1 ); + const void *esi = ( src + len - 1 ); + int discard_ecx; + + /* Assume memmove() is not performance-critical, and perform a + * bytewise copy for simplicity. + */ + __asm__ __volatile__ ( "std\n\t" + "rep movsb\n\t" + "cld\n\t" + : "=&D" ( edi ), "=&S" ( esi ), + "=&c" ( discard_ecx ) + : "0" ( edi ), "1" ( esi ), + "2" ( len ) + : "memory" ); + return dest; +} + + +/** + * Copy (possibly overlapping) memory area + * + * @v dest Destination address + * @v src Source address + * @v len Length + * @ret dest Destination address + */ +void * __memmove ( void *dest, const void *src, size_t len ) { + + if ( dest <= src ) { + return __memcpy ( dest, src, len ); + } else { + return __memcpy_reverse ( dest, src, len ); + } +} + +/** + * Swap memory areas + * + * @v dest Destination address + * @v src Source address + * @v len Length + * @ret dest Destination address + */ +void * memswap ( void *dest, void *src, size_t len ) { + size_t discard_c; + int discard; + + __asm__ __volatile__ ( "\n1:\n\t" + "dec %2\n\t" + "js 2f\n\t" + "movb (%0,%2), %b3\n\t" + "xchgb (%1,%2), %b3\n\t" + "movb %b3, (%0,%2)\n\t" + "jmp 1b\n\t" + "2:\n\t" + : "=r" ( src ), "=r" ( dest ), + "=&c" ( discard_c ), "=&q" ( discard ) + : "0" ( src ), "1" ( dest ), "2" ( len ) + : "memory" ); + + return dest; +} + +/** + * Calculate length of string + * + * @v string String + * @ret len Length (excluding NUL) + */ +size_t strlen ( const char *string ) { + const char *discard_D; + size_t len_plus_one; + + __asm__ __volatile__ ( "repne scasb\n\t" + "not %1\n\t" + : "=&D" ( discard_D ), "=&c" ( len_plus_one ) + : "0" ( string ), "1" ( -1UL ), "a" ( 0 ) ); + + return ( len_plus_one - 1 ); +} + +/** + * Compare strings (up to a specified length) + * + * @v str1 First string + * @v str2 Second string + * @v len Maximum length + * @ret diff Difference + */ +int strncmp ( const char *str1, const char *str2, size_t len ) { + const void *discard_S; + const void *discard_D; + size_t discard_c; + int diff; + + __asm__ __volatile__ ( "\n1:\n\t" + "dec %2\n\t" + "js 2f\n\t" + "lodsb\n\t" + "scasb\n\t" + "jne 3f\n\t" + "testb %b3, %b3\n\t" + "jnz 1b\n\t" + /* Equal */ + "\n2:\n\t" + "xor %3, %3\n\t" + "jmp 4f\n\t" + /* Not equal; CF indicates difference */ + "\n3:\n\t" + "sbb %3, %3\n\t" + "orb $1, %b3\n\t" + "\n4:\n\t" + : "=&S" ( discard_S ), "=&D" ( discard_D ), + "=&c" ( discard_c ), "=&a" ( diff ) + : "0" ( str1 ), "1" ( str2 ), "2" ( len ) ); + + return diff; +} |