$ benchstat 556b3f5/benchonly.txt 2cc17bc/benchonly.txt
name                  old time/op    new time/op    delta
CodeDecoder-8           13.1ms ± 3%    11.5ms ± 1%  -12.36%  (p=0.000 n=29+29)
UnicodeDecoder-8         433ns ± 1%     363ns ± 1%  -16.09%  (p=0.000 n=30+30)
CodeUnmarshalReuse-8    13.0ms ± 1%    11.3ms ± 2%  -13.38%  (p=0.000 n=27+28)

name                  old speed      new speed      delta
CodeDecoder-8          148MB/s ± 3%   169MB/s ± 1%  +14.10%  (p=0.000 n=29+29)
UnicodeDecoder-8      32.3MB/s ± 1%  38.5MB/s ± 1%  +19.20%  (p=0.000 n=29+30)

name                  old alloc/op   new alloc/op   delta
CodeDecoder-8           2.93MB ± 2%    2.77MB ± 2%   -5.15%  (p=0.000 n=28+29)
UnicodeDecoder-8         36.0B ± 0%     36.0B ± 0%     ~     (all equal)
CodeUnmarshalReuse-8    1.96MB ± 0%    1.94MB ± 0%   -0.76%  (p=0.000 n=26+26)

name                  old allocs/op  new allocs/op  delta
CodeDecoder-8            77.8k ± 0%     77.6k ± 0%   -0.28%  (p=0.000 n=28+29)
UnicodeDecoder-8          2.00 ± 0%      2.00 ± 0%     ~     (all equal)
CodeUnmarshalReuse-8     77.8k ± 0%     77.6k ± 0%   -0.22%  (p=0.000 n=26+26)