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Improve memset(3) performance.

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This commit is contained in:
Jonas 'Sortie' Termansen 2014-06-21 20:37:44 +02:00
parent 95fcb94648
commit 73312b201b
1 changed files with 31 additions and 0 deletions
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31
libc/string/memset.cpp
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@ -22,11 +22,42 @@
*******************************************************************************/
#include <stdint.h>
#include <string.h>
#include <__/wordsize.h>
extern "C" void* memset(void* dest_ptr, int value, size_t length)
{
unsigned char* dest = (unsigned char*) dest_ptr;
#if __WORDSIZE == 32 || __WORDSIZE == 64
if ( ((uintptr_t) dest_ptr & (sizeof(unsigned long) - 1)) == 0 )
{
unsigned long* ulong_dest = (unsigned long*) dest;
size_t ulong_length = length / sizeof(unsigned long);
#if __WORDSIZE == 32
unsigned long ulong_value =
(unsigned long) ((unsigned char) value) << 0 |
(unsigned long) ((unsigned char) value) << 8 |
(unsigned long) ((unsigned char) value) << 16 |
(unsigned long) ((unsigned char) value) << 24;
#elif __WORDSIZE == 64
unsigned long ulong_value =
(unsigned long) ((unsigned char) value) << 0 |
(unsigned long) ((unsigned char) value) << 8 |
(unsigned long) ((unsigned char) value) << 16 |
(unsigned long) ((unsigned char) value) << 24 |
(unsigned long) ((unsigned char) value) << 32 |
(unsigned long) ((unsigned char) value) << 40 |
(unsigned long) ((unsigned char) value) << 48 |
(unsigned long) ((unsigned char) value) << 56;
#endif
for ( size_t i = 0; i < ulong_length; i++ )
ulong_dest[i] = ulong_value;
dest += ulong_length * sizeof(unsigned long);
length -= ulong_length * sizeof(unsigned long);
}
#endif
for ( size_t i = 0; i < length; i++ )
dest[i] = (unsigned char) value;
return dest_ptr;