[FFmpeg-devel] [PATCH] skip no-op loop iterations in ff_flac_compute_autocorr

[Bobby Bingham]

Attached patch skips a bunch of iterations which are no-ops because
data1[-lag...-1] are all zero.

Before:
2156850 dezicycles in flac_compute_autocorr, 1 runs, 0 skips
1688165 dezicycles in flac_compute_autocorr, 2 runs, 0 skips
1471100 dezicycles in flac_compute_autocorr, 4 runs, 0 skips
1355148 dezicycles in flac_compute_autocorr, 8 runs, 0 skips
1302561 dezicycles in flac_compute_autocorr, 16 runs, 0 skips
1277819 dezicycles in flac_compute_autocorr, 32 runs, 0 skips
1269022 dezicycles in flac_compute_autocorr, 64 runs, 0 skips
1268782 dezicycles in flac_compute_autocorr, 128 runs, 0 skips
1271836 dezicycles in flac_compute_autocorr, 256 runs, 0 skips
1266946 dezicycles in flac_compute_autocorr, 512 runs, 0 skips
1267474 dezicycles in flac_compute_autocorr, 1024 runs, 0 skips
1280492 dezicycles in flac_compute_autocorr, 2048 runs, 0 skips
1307339 dezicycles in flac_compute_autocorr, 4096 runs, 0 skips
1312491 dezicycles in flac_compute_autocorr, 8191 runs, 1 skips
1303209 dezicycles in flac_compute_autocorr, 16381 runs, 3 skips

After:
2119600 dezicycles in flac_compute_autocorr, 1 runs, 0 skips
1677190 dezicycles in flac_compute_autocorr, 2 runs, 0 skips
1463715 dezicycles in flac_compute_autocorr, 4 runs, 0 skips
1365196 dezicycles in flac_compute_autocorr, 8 runs, 0 skips
1319631 dezicycles in flac_compute_autocorr, 16 runs, 0 skips
1293150 dezicycles in flac_compute_autocorr, 32 runs, 0 skips
1276757 dezicycles in flac_compute_autocorr, 64 runs, 0 skips
1268554 dezicycles in flac_compute_autocorr, 128 runs, 0 skips
1276272 dezicycles in flac_compute_autocorr, 256 runs, 0 skips
1273878 dezicycles in flac_compute_autocorr, 511 runs, 1 skips
1280844 dezicycles in flac_compute_autocorr, 1023 runs, 1 skips
1285053 dezicycles in flac_compute_autocorr, 2047 runs, 1 skips
1278247 dezicycles in flac_compute_autocorr, 4095 runs, 1 skips
1276407 dezicycles in flac_compute_autocorr, 8191 runs, 1 skips
1279592 dezicycles in flac_compute_autocorr, 16383 runs, 1 skips
-- 
Bobby Bingham
Never trust atoms.  Or anything made of atoms.
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