From 714508bcb91057868a96588b9fba4d29c6c4fc77 Mon Sep 17 00:00:00 2001 From: Luca Barbato Date: Thu, 13 Sep 2012 19:45:21 +0200 Subject: [PATCH] vorbisdec: ensure FASTDIV denominator is never 1 In both usages of FASTDIV the denominator might be 1. Using a branch could make the function slower than using a normal division. Both denominator and numerator can be multiplied by 2 safely and using shifts is faster than using a branch. --- libavcodec/vorbisdec.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/libavcodec/vorbisdec.c b/libavcodec/vorbisdec.c index f11e2f5d61..f5a541adae 100644 --- a/libavcodec/vorbisdec.c +++ b/libavcodec/vorbisdec.c @@ -1354,8 +1354,7 @@ static av_always_inline int vorbis_residue_decode_internal(vorbis_context *vc, if (vqbook >= 0 && vc->codebooks[vqbook].codevectors) { unsigned coffs; unsigned dim = vc->codebooks[vqbook].dimensions; - unsigned step = dim == 1 ? vr->partition_size - : FASTDIV(vr->partition_size, dim); + unsigned step = FASTDIV(vr->partition_size << 1, dim << 1); vorbis_codebook codebook = vc->codebooks[vqbook]; if (vr_type == 0) { @@ -1409,7 +1408,7 @@ static av_always_inline int vorbis_residue_decode_internal(vorbis_context *vc, } } else if (vr_type == 2) { - unsigned voffs_div = FASTDIV(voffset, ch); + unsigned voffs_div = FASTDIV(voffset << 1, ch <<1); unsigned voffs_mod = voffset - voffs_div * ch; for (k = 0; k < step; ++k) {