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(Redoing check-in lost by SourceForge's failure.)

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Avoid optimisation errors under -fstrict-aliasing.
This commit is contained in:
Michael Brown 2006-05-13 11:10:24 +00:00
parent 10606e95b3
commit 97d265f8dc
1 changed files with 21 additions and 11 deletions
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32
src/arch/i386/include/bits/string.h
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@ -34,6 +34,16 @@ __memcpy ( void *dest, const void *src, size_t len ) {
static inline __attribute__ (( always_inline )) void *
__constant_memcpy ( void *dest, const void *src, size_t len ) {
union {
uint32_t u32[2];
uint16_t u16[4];
uint8_t u8[8];
} __attribute__ (( __may_alias__ )) *dest_u = dest;
const union {
uint32_t u32[2];
uint16_t u16[4];
uint8_t u8[8];
} __attribute__ (( __may_alias__ )) *src_u = src;
const void *esi;
void *edi;
@ -49,33 +59,33 @@ __constant_memcpy ( void *dest, const void *src, size_t len ) {
*
*/
case 1 : /* 4 bytes */
* ( uint8_t * ) ( dest + 0 ) = * ( uint8_t * ) ( src + 0 );
dest_u->u8[0] = src_u->u8[0];
return dest;
case 2 : /* 6 bytes */
* ( uint16_t * ) ( dest + 0 ) = * ( uint16_t * ) ( src + 0 );
dest_u->u16[0] = src_u->u16[0];
return dest;
case 4 : /* 4 bytes */
* ( uint32_t * ) ( dest + 0 ) = * ( uint32_t * ) ( src + 0 );
dest_u->u32[0] = src_u->u32[0];
return dest;
/*
* Double-register moves; these are probably still a win.
*
*/
case 3 : /* 12 bytes */
* ( uint16_t * ) ( dest + 0 ) = * ( uint16_t * ) ( src + 0 );
* ( uint8_t * ) ( dest + 2 ) = * ( uint8_t * ) ( src + 2 );
dest_u->u16[0] = src_u->u16[0];
dest_u->u8[2] = src_u->u8[2];
return dest;
case 5 : /* 10 bytes */
* ( uint32_t * ) ( dest + 0 ) = * ( uint32_t * ) ( src + 0 );
* ( uint8_t * ) ( dest + 4 ) = * ( uint8_t * ) ( src + 4 );
dest_u->u32[0] = src_u->u32[0];
dest_u->u8[4] = src_u->u8[4];
return dest;
case 6 : /* 12 bytes */
* ( uint32_t * ) ( dest + 0 ) = * ( uint32_t * ) ( src + 0 );
* ( uint16_t * ) ( dest + 4 ) = * ( uint16_t * ) ( src + 4 );
dest_u->u32[0] = src_u->u32[0];
dest_u->u16[2] = src_u->u16[2];
return dest;
case 8 : /* 10 bytes */
* ( uint32_t * ) ( dest + 0 ) = * ( uint32_t * ) ( src + 0 );
* ( uint32_t * ) ( dest + 4 ) = * ( uint32_t * ) ( src + 4 );
dest_u->u32[0] = src_u->u32[0];
dest_u->u32[1] = src_u->u32[1];
return dest;
}