avcodec/me_cmp: Remove ff_check_alignment()

The usage of a static variable presents a potential for data races and
means that this function can't be used in init functions of codecs with
FF_CODEC_CAP_INIT_THREADSAFE (unless of course one presumes that
everything is alright in which case the error is not triggered; but then
the whole function is pointless...). This makes the Snow decoder
init-threadsafe as it already claims.

Notice that this function has been removed in 2014 by Libav in commit
9103185bd1, because only some codepaths
are checked this way and because it only affects legacy compilers. The
latter is of course even more true today.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/me_cmp.c

@@ -1012,31 +1012,8 @@ WRAPPER8_16_SQ(quant_psnr8x8_c, quant_psnr16_c)
 WRAPPER8_16_SQ(rd8x8_c, rd16_c)
 WRAPPER8_16_SQ(bit8x8_c, bit16_c)
 
-int ff_check_alignment(void)
-{
-    static int did_fail = 0;
-    LOCAL_ALIGNED_16(int, aligned, [4]);
-
-    if ((intptr_t)aligned & 15) {
-        if (!did_fail) {
-#if HAVE_MMX || HAVE_ALTIVEC
-            av_log(NULL, AV_LOG_ERROR,
-                "Compiler did not align stack variables. Libavcodec has been miscompiled\n"
-                "and may be very slow or crash. This is not a bug in libavcodec,\n"
-                "but in the compiler. You may try recompiling using gcc >= 4.2.\n"
-                "Do not report crashes to FFmpeg developers.\n");
-#endif
-            did_fail=1;
-        }
-        return -1;
-    }
-    return 0;
-}
-
 av_cold void ff_me_cmp_init(MECmpContext *c, AVCodecContext *avctx)
 {
-    ff_check_alignment();
-
     c->sum_abs_dctelem = sum_abs_dctelem_c;
 
     /* TODO [0] 16  [1] 8 */

libavcodec/me_cmp.h

@@ -79,8 +79,6 @@ typedef struct MECmpContext {
     me_cmp_func median_sad[6];
 } MECmpContext;
 
-int ff_check_alignment(void);
-
 void ff_me_cmp_init(MECmpContext *c, AVCodecContext *avctx);
 void ff_me_cmp_init_alpha(MECmpContext *c, AVCodecContext *avctx);
 void ff_me_cmp_init_arm(MECmpContext *c, AVCodecContext *avctx);

libavcodec/mpegvideo_enc.c

@@ -2786,8 +2786,6 @@ static int pre_estimate_motion_thread(AVCodecContext *c, void *arg){
 static int estimate_motion_thread(AVCodecContext *c, void *arg){
     MpegEncContext *s= *(void**)arg;
 
-    ff_check_alignment();
-
     s->me.dia_size= s->avctx->dia_size;
     s->first_slice_line=1;
     for(s->mb_y= s->start_mb_y; s->mb_y < s->end_mb_y; s->mb_y++) {
@@ -2814,8 +2812,6 @@ static int mb_var_thread(AVCodecContext *c, void *arg){
     MpegEncContext *s= *(void**)arg;
     int mb_x, mb_y;
 
-    ff_check_alignment();
-
     for(mb_y=s->start_mb_y; mb_y < s->end_mb_y; mb_y++) {
         for(mb_x=0; mb_x < s->mb_width; mb_x++) {
             int xx = mb_x * 16;
@@ -2944,8 +2940,6 @@ static int encode_thread(AVCodecContext *c, void *arg){
     uint8_t bit_buf_tex[2][MAX_MB_BYTES];
     PutBitContext pb[2], pb2[2], tex_pb[2];
 
-    ff_check_alignment();
-
     for(i=0; i<2; i++){
         init_put_bits(&pb    [i], bit_buf    [i], MAX_MB_BYTES);
         init_put_bits(&pb2   [i], bit_buf2   [i], MAX_MB_BYTES);