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lavc/jrevdct: Avoid an aliasing violation. 

Fixes fate on different PowerPC systems with some compilers.

Analyzed-by: Lauri Kasanen
This commit is contained in:
Carl Eugen Hoyos 2018-11-26 00:43:46 +01:00
parent fd2d6f376d
commit 5a7617136a
1 changed files with 9 additions and 8 deletions
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17
libavcodec/jrevdct.c
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@ -63,6 +63,7 @@
*/
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "dct.h"
#include "idctdsp.h"
@ -234,7 +235,7 @@ void ff_j_rev_dct(DCTBLOCK data)
* row DCT calculations can be simplified this way.
*/
register int *idataptr = (int*)dataptr;
register uint8_t *idataptr = (uint8_t*)dataptr;
/* WARNING: we do the same permutation as MMX idct to simplify the
video core */
@ -254,10 +255,10 @@ void ff_j_rev_dct(DCTBLOCK data)
int16_t dcval = (int16_t) (d0 * (1 << PASS1_BITS));
register int v = (dcval & 0xffff) | ((dcval * (1 << 16)) & 0xffff0000);
idataptr[0] = v;
idataptr[1] = v;
idataptr[2] = v;
idataptr[3] = v;
AV_WN32A(&idataptr[ 0], v);
AV_WN32A(&idataptr[ 4], v);
AV_WN32A(&idataptr[ 8], v);
AV_WN32A(&idataptr[12], v);
}
dataptr += DCTSIZE; /* advance pointer to next row */
@ -974,7 +975,7 @@ void ff_j_rev_dct4(DCTBLOCK data)
* row DCT calculations can be simplified this way.
*/
register int *idataptr = (int*)dataptr;
register uint8_t *idataptr = (uint8_t*)dataptr;
d0 = dataptr[0];
d2 = dataptr[1];
@ -988,8 +989,8 @@ void ff_j_rev_dct4(DCTBLOCK data)
int16_t dcval = (int16_t) (d0 << PASS1_BITS);
register int v = (dcval & 0xffff) | ((dcval << 16) & 0xffff0000);
idataptr[0] = v;
idataptr[1] = v;
AV_WN32A(&idataptr[0], v);
AV_WN32A(&idataptr[4], v);
}
dataptr += DCTSTRIDE; /* advance pointer to next row */