[libav-devel] [PATCH 1/2] golomb: Optimize get_ue/se_golomb

[Diego Biurrun]

From: Alexandra Hájková <alexan...@khirnov.net>

Do not prefetch data too often for short codes.
---
 libavcodec/golomb.h | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/libavcodec/golomb.h b/libavcodec/golomb.h
index 648f924..cbb5d12 100644
--- a/libavcodec/golomb.h
+++ b/libavcodec/golomb.h
@@ -54,20 +54,20 @@ static inline int get_ue_golomb(BitstreamContext *bc)
 {
     unsigned int buf;
 
-    buf = bitstream_peek(bc, 32);
+    buf = bitstream_peek(bc, 9);
 
-    if (buf >= (1 << 27)) {
-        buf >>= 32 - 9;
+    if (buf >= (1 << 4)) {
         bitstream_skip(bc, ff_golomb_vlc_len[buf]);
 
         return ff_ue_golomb_vlc_code[buf];
     } else {
-        int log = 2 * av_log2(buf) - 31;
-        buf >>= log;
-        buf--;
+        unsigned int buf2 = bitstream_peek(bc, 32);
+        int log = 2 * av_log2(buf2) - 31;
+        buf2 >>= log;
+        buf2--;
         bitstream_skip(bc, 32 - log);
 
-        return buf;
+        return buf2;
     }
 }
 
@@ -167,25 +167,25 @@ static inline int get_se_golomb(BitstreamContext *bc)
 {
     unsigned int buf;
 
-    buf = bitstream_peek(bc, 32);
+    buf = bitstream_peek(bc, 9);
 
-    if (buf >= (1 << 27)) {
-        buf >>= 32 - 9;
+    if (buf >= (1 << 4)) {
         bitstream_skip(bc, ff_golomb_vlc_len[buf]);
 
         return ff_se_golomb_vlc_code[buf];
     } else {
-        int log = 2 * av_log2(buf) - 31;
-        buf >>= log;
+        unsigned int buf2 = bitstream_peek(bc, 32);
+        int log = 2 * av_log2(buf2) - 31;
+        buf2 >>= log;
 
         bitstream_skip(bc, 32 - log);
 
-        if (buf & 1)
-            buf = -(buf >> 1);
+        if (buf2 & 1)
+            buf2 = -(buf2 >> 1);
         else
-            buf = (buf >> 1);
+            buf2 = (buf2 >> 1);
 
-        return buf;
+        return buf2;
     }
 }
 
-- 
2.1.4

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