Avoid branch in 'num_bits == 0' branch when peeking bits

diff --git a/include/wimlib/decompress_common.h b/include/wimlib/decompress_common.h
index 420f7f41e3adf8a207248241a41aee0db3ee3879..ce731dca39ba40cc4c3c92c2f5a973a6fd59084a 100644 (file)
--- a/include/wimlib/decompress_common.h
+++ b/include/wimlib/decompress_common.h
@@ -90,9 +90,7 @@ overflow:
 static inline u32
 bitstream_peek_bits(const struct input_bitstream *is, const unsigned num_bits)
 {
 static inline u32
 bitstream_peek_bits(const struct input_bitstream *is, const unsigned num_bits)
 {

-       if (unlikely(num_bits == 0))
-               return 0;
-       return is->bitbuf >> (32 - num_bits);
+       return (is->bitbuf >> 1) >> (sizeof(is->bitbuf) * 8 - num_bits - 1);

 }
 
 /* Remove @num_bits from the bitstream.  There must be at least @num_bits
 }
 
 /* Remove @num_bits from the bitstream.  There must be at least @num_bits

diff --git a/src/lzms_decompress.c b/src/lzms_decompress.c
index 7f82803c9339b61d06da48756b45767ae12fa30d..bd7e76e12e809dcbd222baf08557ebce51990717 100644 (file)
--- a/src/lzms_decompress.c
+++ b/src/lzms_decompress.c
@@ -430,9 +430,7 @@ lzms_ensure_bits(struct lzms_input_bitstream *is, unsigned num_bits)
 static inline bitbuf_t
 lzms_peek_bits(struct lzms_input_bitstream *is, unsigned num_bits)
 {
 static inline bitbuf_t
 lzms_peek_bits(struct lzms_input_bitstream *is, unsigned num_bits)
 {

-       if (unlikely(num_bits == 0))
-               return 0;
-       return is->bitbuf >> (sizeof(is->bitbuf) * 8 - num_bits);
+       return (is->bitbuf >> 1) >> (sizeof(is->bitbuf) * 8 - num_bits - 1);

 }
 
 /* Remove @num_bits bits from the bitbuffer variable.  */
 }
 
 /* Remove @num_bits bits from the bitbuffer variable.  */