[issue21955] ceval.c: implement fast path for integers with a single digit

[STINNER Victor]

STINNER Victor added the comment:

Result of performance 0.3.3 (and perf 0.8.3).

No major benchmark is faster. A few benchmarks seem to be event slower using fastint6.patch (but I don't really trust pybench).


== fastint6.patch ==

$ python3 -m perf compare_to master.json fastint6.json --group-by-speed --min-speed=5
Slower (3):
- pybench.ConcatUnicode: 52.7 ns +- 0.0 ns -> 56.1 ns +- 0.4 ns: 1.06x slower
- pybench.ConcatStrings: 52.7 ns +- 0.3 ns -> 56.1 ns +- 0.1 ns: 1.06x slower
- pybench.CompareInternedStrings: 16.5 ns +- 0.0 ns -> 17.4 ns +- 0.0 ns: 1.05x slower

Faster (4):
- pybench.SimpleIntFloatArithmetic: 441 ns +- 2 ns -> 400 ns +- 6 ns: 1.10x faster
- pybench.SimpleIntegerArithmetic: 441 ns +- 2 ns -> 401 ns +- 5 ns: 1.10x faster
- pybench.SimpleLongArithmetic: 643 ns +- 4 ns -> 608 ns +- 6 ns: 1.06x faster
- genshi_text: 79.6 ms +- 0.5 ms -> 75.5 ms +- 0.8 ms: 1.05x faster

Benchmark hidden because not significant (114): 2to3, call_method, (...)


== inline2.patch ==

haypo at selma$ python3 -m perf compare_to master.json inline2.json --group-by-speed --min-speed=5
Faster (2):
- spectral_norm: 223 ms +- 1 ms -> 209 ms +- 1 ms: 1.07x faster
- pybench.SimpleLongArithmetic: 643 ns +- 4 ns -> 606 ns +- 7 ns: 1.06x faster

Benchmark hidden because not significant (119): 2to3, call_method, (...)

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<http://bugs.python.org/issue21955>
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