Significant degradations, abandoned.

```
λ benchcmp before.txt after.txt
benchmark                                            old ns/op     new ns/op     delta
BenchmarkDecompress4XNoTable/digits-32               166962        183522        +9.92%
BenchmarkDecompress4XNoTable/gettysburg-32           2747          2783          +1.31%
BenchmarkDecompress4XNoTable/twain-32                579833        581783        +0.34%
BenchmarkDecompress4XNoTable/low-ent.10k-32          56815         65143         +14.66%
BenchmarkDecompress4XNoTable/superlow-ent-10k-32     15217         17399         +14.34%
BenchmarkDecompress4XNoTable/case1-32                223           215           -3.63%
BenchmarkDecompress4XNoTable/case2-32                178           173           -3.03%
BenchmarkDecompress4XNoTable/case3-32                186           178           -4.10%
BenchmarkDecompress4XNoTable/pngdata.001-32          78199         79470         +1.63%
BenchmarkDecompress4XNoTable/normcount2-32           295           280           -5.22%
BenchmarkDecompress4XTable/digits-32                 169105        186653        +10.38%
BenchmarkDecompress4XTable/gettysburg-32             4113          4243          +3.16%
BenchmarkDecompress4XTable/twain-32                  580482        589091        +1.48%
BenchmarkDecompress4XTable/low-ent.10k-32            57488         66318         +15.36%
BenchmarkDecompress4XTable/superlow-ent-10k-32       15801         18111         +14.62%
BenchmarkDecompress4XTable/case1-32                  2060          2062          +0.10%
BenchmarkDecompress4XTable/case2-32                  2004          2015          +0.55%
BenchmarkDecompress4XTable/case3-32                  2026          2040          +0.69%
BenchmarkDecompress4XTable/pngdata.001-32            81603         83582         +2.43%
BenchmarkDecompress4XTable/normcount2-32             1426          1401          -1.75%
```