On 2014-02-14 16:03:11 +0000, Christophe Gisquet wrote:
> The codeblock affected accounted for around 4% of the runtime on x86_64
> (measured using oprofile on a Penryn).
> Timings for Arrandale (gcc 4.6.1 tdm64-1 for windows):
> win32: 341 -> 331
> win64: 321 -> 120
>
> The compiled loops are completely unrolled, so only unrolling the
> initialization causes an improvement.
> ---
> libavcodec/dcadec.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/libavcodec/dcadec.c b/libavcodec/dcadec.c
> index c251db8..2d88cb4 100644
> --- a/libavcodec/dcadec.c
> +++ b/libavcodec/dcadec.c
> @@ -1193,15 +1193,21 @@ static int dca_subsubframe(DCAContext *s, int
> base_channel, int block_index)
> if (s->prediction_mode[k][l]) {
> int n;
> for (m = 0; m < 8; m++) {
> - for (n = 1; n <= 4; n++)
> + float sum;
> + if (m >= 1)
> + sum = adpcm_vb[s->prediction_vq[k][l]][1 - 1] *
> + subband_samples[k][l][m - 1];
> + else if (s->predictor_history)
> + sum = adpcm_vb[s->prediction_vq[k][l]][1 - 1] *
> + s->subband_samples_hist[k][l][m - 1 + 4];
can s->predictor_history be 0? if yes sum is uninitialized for m == 0 and used
later
> + for (n = 2; n <= 4; n++)
> if (m >= n)
> - subband_samples[k][l][m] +=
> - (adpcm_vb[s->prediction_vq[k][l]][n - 1] *
> - subband_samples[k][l][m - n] / 8192);
> + sum += adpcm_vb[s->prediction_vq[k][l]][n - 1] *
> + subband_samples[k][l][m - n];
> else if (s->predictor_history)
> - subband_samples[k][l][m] +=
> - (adpcm_vb[s->prediction_vq[k][l]][n - 1] *
> - s->subband_samples_hist[k][l][m - n + 4] /
> 8192);
> + sum += adpcm_vb[s->prediction_vq[k][l]][n - 1] *
> + s->subband_samples_hist[k][l][m - n + 4];
> + subband_samples[k][l][m] += sum * 1.0f/ 8192;
please add a space between 1.0f and /
Janne
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