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Fixed crash with movaps instruction in SDL_memcpy(), due to unaligned Uint32* cast and -O3 vectorization optimizations with gcc 4.9.0

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This commit is contained in:
Sam Lantinga 2013-05-27 16:18:11 -07:00
parent 21512a77b7
commit b3ec1b660b
1 changed files with 40 additions and 20 deletions
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60
src/stdlib/SDL_string.c
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@ -310,29 +310,49 @@ void *SDL_memcpy(void *dst, const void *src, size_t len) { return SDL_memcpy_inl
void *
SDL_memcpy(void *dst, const void *src, size_t len)
{
size_t left = (len % 4);
Uint32 *srcp4, *dstp4;
Uint8 *srcp1, *dstp1;
#ifdef __GNUC__
/* Presumably this is well tuned for speed.
On my machine this is twice as fast as the C code below.
*/
return __builtin_memcpy(dst, src, len);
#else
/* GCC 4.9.0 with -O3 will generate movaps instructions with the loop
using Uint32* pointers, so we need to make sure the pointers are
aligned before we loop using them.
*/
if (((intptr_t)src & 0x3) || ((intptr_t)dst & 0x3)) {
/* Do an unaligned byte copy */
Uint8 *srcp1 = (Uint8 *)src;
Uint8 *dstp1 = (Uint8 *)dst;
srcp4 = (Uint32 *) src;
dstp4 = (Uint32 *) dst;
len /= 4;
while (len--) {
*dstp4++ = *srcp4++;
while (len--) {
*dstp1++ = *srcp1++;
}
} else {
size_t left = (len % 4);
Uint32 *srcp4, *dstp4;
Uint8 *srcp1, *dstp1;
srcp4 = (Uint32 *) src;
dstp4 = (Uint32 *) dst;
len /= 4;
while (len--) {
*dstp4++ = *srcp4++;
}
srcp1 = (Uint8 *) srcp4;
dstp1 = (Uint8 *) dstp4;
switch (left) {
case 3:
*dstp1++ = *srcp1++;
case 2:
*dstp1++ = *srcp1++;
case 1:
*dstp1++ = *srcp1++;
}
}
srcp1 = (Uint8 *) srcp4;
dstp1 = (Uint8 *) dstp4;
switch (left) {
case 3:
*dstp1++ = *srcp1++;
case 2:
*dstp1++ = *srcp1++;
case 1:
*dstp1++ = *srcp1++;
}
return dst;
#endif /* __GNUC__ */
}
#endif