benchmark                           old ns/op    new ns/op    delta
BenchmarkDecodeDigitsSpeed1e4          197767       203490   +2.89%
BenchmarkDecodeDigitsSpeed1e5         1873969      1912761   +2.07%
BenchmarkDecodeDigitsSpeed1e6        18922760     19021056   +0.52%
BenchmarkDecodeDigitsDefault1e4        194975       197054   +1.07%
BenchmarkDecodeDigitsDefault1e5       1704262      1719988   +0.92%
BenchmarkDecodeDigitsDefault1e6      16618354     16351957   -1.60%
BenchmarkDecodeDigitsCompress1e4       195281       194626   -0.34%
BenchmarkDecodeDigitsCompress1e5      1694364      1702372   +0.47%
BenchmarkDecodeDigitsCompress1e6     16463347     16492126   +0.17%
BenchmarkDecodeTwainSpeed1e4           200653       200127   -0.26%
BenchmarkDecodeTwainSpeed1e5          1861385      1759632   -5.47%
BenchmarkDecodeTwainSpeed1e6         18255769     17186679   -5.86%
BenchmarkDecodeTwainDefault1e4         189080       185157   -2.07%
BenchmarkDecodeTwainDefault1e5        1559222      1461465   -6.27%
BenchmarkDecodeTwainDefault1e6       14792125     13879051   -6.17%
BenchmarkDecodeTwainCompress1e4        188881       185151   -1.97%
BenchmarkDecodeTwainCompress1e5       1537031      1456945   -5.21%
BenchmarkDecodeTwainCompress1e6      14805972     13405094   -9.46%
BenchmarkPaeth                          4            4   -0.89%
BenchmarkDecodeGray                964679       937244   -2.84%
BenchmarkDecodeNRGBAGradient      3753769      3646416   -2.86%
BenchmarkDecodeNRGBAOpaque        3165856      2981300   -5.83%
BenchmarkDecodePaletted            713950       691984   -3.08%
BenchmarkDecodeRGB                3051718      2924260   -4.18%

R=nigeltao, bradfitz
CC=golang-dev, raph
https://golang.org/cl/9425046