get_bits: remove A32 variant

The A32 bitstream reader variant is only used on ARMv5 and for
Prores due to the larger bit cache this decoder requires.

In benchmarks on ARMv5 (Marvell Sheeva) with gcc 4.6, the only
statistically significant difference between ALT and A32 is
a 4% advantage for ALT in FLAC decoding.  There is thus no (longer)
any reason to keep the A32 reader from this point of view.

This patch adds an option to the ALT reader increasing the bit
cache to 32 bits as required by the Prores decoder.  Benchmarking
shows no significant change in speed on Intel i7.  Again, the
A32 reader fails to justify its existence.

Signed-off-by: Mans Rullgard <mans@mansr.com>

4 files changed, 16 insertions, 100 deletions

diff --git a/libavcodec/dv.c b/libavcodec/dv.c
index 6c50f77d3f..76825f51ee 100644
--- a/libavcodec/dv.c
+++ b/libavcodec/dv.c
@@ -37,7 +37,7 @@
  * @file
  * DV codec.
  */
-#define ALT_BITSTREAM_READER
+
 #include "libavutil/pixdesc.h"
 #include "avcodec.h"
 #include "dsputil.h"
diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
index 4c03e412ce..684cc992fe 100644
--- a/libavcodec/get_bits.h
+++ b/libavcodec/get_bits.h
@@ -35,31 +35,11 @@
 #include "libavutil/log.h"
 #include "mathops.h"
 
-#if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
-#   define ALT_BITSTREAM_READER
-#endif
-
-#if !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
-#   if ARCH_ARM && !HAVE_FAST_UNALIGNED
-#       define A32_BITSTREAM_READER
-#   else
-#       define ALT_BITSTREAM_READER
-//#define A32_BITSTREAM_READER
-#   endif
-#endif
-
 /* bit input */
 /* buffer, buffer_end and size_in_bits must be present and used by every reader */
 typedef struct GetBitContext {
     const uint8_t *buffer, *buffer_end;
-#ifdef ALT_BITSTREAM_READER
     int index;
-#elif defined A32_BITSTREAM_READER
-    uint32_t *buffer_ptr;
-    uint32_t cache0;
-    uint32_t cache1;
-    int bit_count;
-#endif
     int size_in_bits;
 } GetBitContext;
 
@@ -122,8 +102,11 @@ LAST_SKIP_BITS(name, gb, num)
 for examples see get_bits, show_bits, skip_bits, get_vlc
 */
 
-#ifdef ALT_BITSTREAM_READER
+#ifdef LONG_BITSTREAM_READER
+#   define MIN_CACHE_BITS 32
+#else
 #   define MIN_CACHE_BITS 25
+#endif
 
 #   define OPEN_READER(name, gb)                \
     unsigned int name##_index = (gb)->index;    \
@@ -132,13 +115,23 @@ for examples see get_bits, show_bits, skip_bits, get_vlc
 #   define CLOSE_READER(name, gb) (gb)->index = name##_index
 
 # ifdef ALT_BITSTREAM_READER_LE
+# ifdef LONG_BITSTREAM_READER
+#   define UPDATE_CACHE(name, gb) \
+    name##_cache = AV_RL64((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
+# else
 #   define UPDATE_CACHE(name, gb) \
     name##_cache = AV_RL32((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
+# endif
 
 #   define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
 # else
+# ifdef LONG_BITSTREAM_READER
+#   define UPDATE_CACHE(name, gb) \
+    name##_cache = AV_RB64((gb)->buffer+(name##_index >> 3)) >> (32 - (name##_index & 0x07))
+# else
 #   define UPDATE_CACHE(name, gb) \
     name##_cache = AV_RB32((gb)->buffer+(name##_index>>3)) << (name##_index&0x07)
+# endif
 
 #   define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
 # endif
@@ -174,72 +167,6 @@ static inline void skip_bits_long(GetBitContext *s, int n){
     s->index += n;
 }
 
-#elif defined A32_BITSTREAM_READER
-
-#   define MIN_CACHE_BITS 32
-
-#   define OPEN_READER(name, gb)                        \
-    int name##_bit_count        = (gb)->bit_count;      \
-    uint32_t name##_cache0      = (gb)->cache0;         \
-    uint32_t name##_cache1      = (gb)->cache1;         \
-    uint32_t *name##_buffer_ptr = (gb)->buffer_ptr
-
-#   define CLOSE_READER(name, gb) do {          \
-        (gb)->bit_count  = name##_bit_count;    \
-        (gb)->cache0     = name##_cache0;       \
-        (gb)->cache1     = name##_cache1;       \
-        (gb)->buffer_ptr = name##_buffer_ptr;   \
-    } while (0)
-
-#   define UPDATE_CACHE(name, gb) do {                                  \
-        if(name##_bit_count > 0){                                       \
-            const uint32_t next = av_be2ne32(*name##_buffer_ptr);       \
-            name##_cache0 |= NEG_USR32(next, name##_bit_count);         \
-            name##_cache1 |= next << name##_bit_count;                  \
-            name##_buffer_ptr++;                                        \
-            name##_bit_count -= 32;                                     \
-        }                                                               \
-    } while (0)
-
-#   define SKIP_CACHE(name, gb, num) do {               \
-        name##_cache0 <<= (num);                        \
-        name##_cache0 |= NEG_USR32(name##_cache1,num);  \
-        name##_cache1 <<= (num);                        \
-    } while (0)
-
-#   define SKIP_COUNTER(name, gb, num) name##_bit_count += (num)
-
-#   define SKIP_BITS(name, gb, num) do {        \
-        SKIP_CACHE(name, gb, num);              \
-        SKIP_COUNTER(name, gb, num);            \
-    } while (0)
-
-#   define LAST_SKIP_BITS(name, gb, num)  SKIP_BITS(name, gb, num)
-#   define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
-
-#   define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache0, num)
-
-#   define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache0, num)
-
-#   define GET_CACHE(name, gb) name##_cache0
-
-static inline int get_bits_count(const GetBitContext *s) {
-    return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
-}
-
-static inline void skip_bits_long(GetBitContext *s, int n){
-    OPEN_READER(re, s);
-    re_bit_count += n;
-    re_buffer_ptr += re_bit_count>>5;
-    re_bit_count &= 31;
-    re_cache0 = av_be2ne32(re_buffer_ptr[-1]) << re_bit_count;
-    re_cache1 = 0;
-    UPDATE_CACHE(re, s);
-    CLOSE_READER(re, s);
-}
-
-#endif
-
 /**
  * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
  * if MSB not set it is negative
@@ -301,7 +228,6 @@ static inline void skip_bits(GetBitContext *s, int n){
 }
 
 static inline unsigned int get_bits1(GetBitContext *s){
-#ifdef ALT_BITSTREAM_READER
     unsigned int index = s->index;
     uint8_t result = s->buffer[index>>3];
 #ifdef ALT_BITSTREAM_READER_LE
@@ -315,9 +241,6 @@ static inline unsigned int get_bits1(GetBitContext *s){
     s->index = index;
 
     return result;
-#else
-    return get_bits(s, 1);
-#endif
 }
 
 static inline unsigned int show_bits1(GetBitContext *s){
@@ -392,13 +315,7 @@ static inline void init_get_bits(GetBitContext *s,
     s->buffer       = buffer;
     s->size_in_bits = bit_size;
     s->buffer_end   = buffer + buffer_size;
-#ifdef ALT_BITSTREAM_READER
     s->index        = 0;
-#elif defined A32_BITSTREAM_READER
-    s->buffer_ptr   = (uint32_t*)((intptr_t)buffer & ~3);
-    s->bit_count    = 32 +     8*((intptr_t)buffer &  3);
-    skip_bits_long(s, 0);
-#endif
 }
 
 static inline void align_get_bits(GetBitContext *s)
diff --git a/libavcodec/imc.c b/libavcodec/imc.c
index b55eee9b70..ff8e31e9e6 100644
--- a/libavcodec/imc.c
+++ b/libavcodec/imc.c
@@ -35,7 +35,6 @@
 #include <stddef.h>
 #include <stdio.h>
 
-#define ALT_BITSTREAM_READER
 #include "avcodec.h"
 #include "get_bits.h"
 #include "dsputil.h"
diff --git a/libavcodec/proresdec.c b/libavcodec/proresdec.c
index adadcf8b75..031760c3bb 100644
--- a/libavcodec/proresdec.c
+++ b/libavcodec/proresdec.c
@@ -28,7 +28,7 @@
  * @see http://wiki.multimedia.cx/index.php?title=Apple_ProRes
  */
 
-#define A32_BITSTREAM_READER // some ProRes vlc codes require up to 28 bits to be read at once
+#define LONG_BITSTREAM_READER // some ProRes vlc codes require up to 28 bits to be read at once
 
 #include <stdint.h>