diff --git a/libavcodec/dca_core.c b/libavcodec/dca_core.c
index 60508fabb9..5dd727fc72 100644
--- a/libavcodec/dca_core.c
+++ b/libavcodec/dca_core.c
@@ -770,10 +770,6 @@ static void erase_adpcm_history(DCACoreDecoder *s)
     for (ch = 0; ch < DCA_CHANNELS; ch++)
         for (band = 0; band < DCA_SUBBANDS; band++)
             AV_ZERO128(s->subband_samples[ch][band] - DCA_ADPCM_COEFFS);
-
-#ifdef FF_COPY_SWAP_ZERO_USES_MMX
-    emms_c();
-#endif
 }
 
 static int alloc_sample_buffer(DCACoreDecoder *s)
@@ -837,10 +833,6 @@ static int parse_frame_data(DCACoreDecoder *s, enum HeaderType header, int xch_b
         }
     }
 
-#ifdef FF_COPY_SWAP_ZERO_USES_MMX
-    emms_c();
-#endif
-
     return 0;
 }
 
@@ -1283,10 +1275,6 @@ static void erase_x96_adpcm_history(DCACoreDecoder *s)
     for (ch = 0; ch < DCA_CHANNELS; ch++)
         for (band = 0; band < DCA_SUBBANDS_X96; band++)
             AV_ZERO128(s->x96_subband_samples[ch][band] - DCA_ADPCM_COEFFS);
-
-#ifdef FF_COPY_SWAP_ZERO_USES_MMX
-    emms_c();
-#endif
 }
 
 static int alloc_x96_sample_buffer(DCACoreDecoder *s)
@@ -1516,10 +1504,6 @@ static int parse_x96_frame_data(DCACoreDecoder *s, int exss, int xch_base)
         }
     }
 
-#ifdef FF_COPY_SWAP_ZERO_USES_MMX
-    emms_c();
-#endif
-
     return 0;
 }
 
diff --git a/libavutil/x86/intreadwrite.h b/libavutil/x86/intreadwrite.h
index 40f375b013..5e57d6a8cd 100644
--- a/libavutil/x86/intreadwrite.h
+++ b/libavutil/x86/intreadwrite.h
@@ -27,42 +27,6 @@
 
 #if HAVE_MMX
 
-#if !HAVE_FAST_64BIT && defined(__MMX__)
-
-#define FF_COPY_SWAP_ZERO_USES_MMX
-
-#define AV_COPY64 AV_COPY64
-static av_always_inline void AV_COPY64(void *d, const void *s)
-{
-    __asm__("movq   %1, %%mm0  \n\t"
-            "movq   %%mm0, %0  \n\t"
-            : "=m"(*(uint64_t*)d)
-            : "m" (*(const uint64_t*)s)
-            : "mm0");
-}
-
-#define AV_SWAP64 AV_SWAP64
-static av_always_inline void AV_SWAP64(void *a, void *b)
-{
-    __asm__("movq   %1, %%mm0  \n\t"
-            "movq   %0, %%mm1  \n\t"
-            "movq   %%mm0, %0  \n\t"
-            "movq   %%mm1, %1  \n\t"
-            : "+m"(*(uint64_t*)a), "+m"(*(uint64_t*)b)
-            ::"mm0", "mm1");
-}
-
-#define AV_ZERO64 AV_ZERO64
-static av_always_inline void AV_ZERO64(void *d)
-{
-    __asm__("pxor %%mm0, %%mm0  \n\t"
-            "movq %%mm0, %0     \n\t"
-            : "=m"(*(uint64_t*)d)
-            :: "mm0");
-}
-
-#endif /* !HAVE_FAST_64BIT && defined(__MMX__) */
-
 #ifdef __SSE__
 
 #define AV_COPY128 AV_COPY128