[FFmpeg-cvslog] avcodec/e?ac3enc: Inform compiler about PutBitContext being blank

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Fri May 24 16:43:31 2024 +0200| [2df9c8da72d59ff1be58ded85674d58d2ed69bdb] | committer: Andreas Rheinhardt

avcodec/e?ac3enc: Inform compiler about PutBitContext being blank

This turned out to be very beneficial: For GCC 13, the codesize
of ac3_output_frame_header went down from 4522B to 1247B and
from 10762B to 9298B for eac3_output_frame_header. For Clang 17,
the numbers went down from 3923B to 2477B and from 8338B to 6548B
(always with -O3).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2df9c8da72d59ff1be58ded85674d58d2ed69bdb
---

 libavcodec/ac3enc.c  | 2 ++
 libavcodec/eac3enc.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/libavcodec/ac3enc.c b/libavcodec/ac3enc.c
index 3649289865..a1783577c5 100644
--- a/libavcodec/ac3enc.c
+++ b/libavcodec/ac3enc.c
@@ -1638,6 +1638,8 @@ static void ac3_output_frame_header(AC3EncodeContext *s, PutBitContext *pb)
 {
     AC3EncOptions *opt = &s->options;
 
+    put_bits_assume_flushed(pb);
+
     put_bits(pb, 16, 0x0b77);   /* frame header */
     put_bits(pb, 16, 0);        /* crc1: will be filled later */
     put_bits(pb, 2,  s->bit_alloc.sr_code);
diff --git a/libavcodec/eac3enc.c b/libavcodec/eac3enc.c
index 3590b821a3..10b1ab337c 100644
--- a/libavcodec/eac3enc.c
+++ b/libavcodec/eac3enc.c
@@ -135,6 +135,8 @@ static void eac3_output_frame_header(AC3EncodeContext *s, PutBitContext *pb)
     int blk, ch;
     AC3EncOptions *opt = &s->options;
 
+    put_bits_assume_flushed(pb);
+
     put_bits(pb, 16, 0x0b77);                   /* sync word */
 
     /* BSI header */