--- /dev/null
+/*
+ * 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;
+}
Code Review / kvmfornfv.git / blobdiff