This allows the bit-state executions to have their
own pool of allocated structures. A step toward
eliminating the per-Regexp machine cache.

Note especially the -92% on MatchParallelShared.
This is real but not a complete story: the other
execution engines still need to be de-shared,
but the benchmark was only using bit-state.

The tiny slowdowns in unrelated code are noise.

name                             old time/op    new time/op    delta
Find-12                             264ns ± 3%     254ns ± 0%   -3.86%  (p=0.000 n=10+9)
FindAllNoMatches-12                 140ns ± 2%     135ns ± 0%   -3.91%  (p=0.000 n=10+9)
FindString-12                       256ns ± 0%     247ns ± 0%   -3.52%  (p=0.000 n=8+8)
FindSubmatch-12                     339ns ± 1%     334ns ± 0%   -1.41%  (p=0.000 n=9+10)
FindStringSubmatch-12               322ns ± 0%     321ns ± 0%   -0.21%  (p=0.005 n=8+9)
Literal-12                          100ns ± 2%      92ns ± 0%   -8.10%  (p=0.000 n=10+9)
NotLiteral-12                      1.50µs ± 0%    1.47µs ± 0%   -1.91%  (p=0.000 n=8+9)
MatchClass-12                      2.18µs ± 0%    2.17µs ± 0%   -0.20%  (p=0.001 n=10+7)
MatchClass_InRange-12              2.12µs ± 0%    2.13µs ± 0%   +0.23%  (p=0.000 n=10+10)
ReplaceAll-12                      1.41µs ± 0%    1.39µs ± 0%   -1.30%  (p=0.000 n=7+10)
AnchoredLiteralShortNonMatch-12    89.8ns ± 0%    83.2ns ± 0%   -7.35%  (p=0.000 n=8+8)
AnchoredLiteralLongNonMatch-12      105ns ± 3%     105ns ± 0%     ~     (p=0.186 n=10+10)
AnchoredShortMatch-12               141ns ± 0%     131ns ± 0%   -7.09%  (p=0.000 n=9+10)
AnchoredLongMatch-12                276ns ± 4%     267ns ± 0%   -3.23%  (p=0.000 n=10+10)
OnePassShortA-12                    620ns ± 0%     611ns ± 0%   -1.39%  (p=0.000 n=10+9)
NotOnePassShortA-12                 575ns ± 3%     552ns ± 0%   -3.97%  (p=0.000 n=10+8)
OnePassShortB-12                    493ns ± 0%     491ns ± 0%   -0.33%  (p=0.000 n=8+8)
NotOnePassShortB-12                 423ns ± 0%     412ns ± 0%   -2.60%  (p=0.000 n=8+9)
OnePassLongPrefix-12                112ns ± 0%     112ns ± 0%     ~     (all equal)
OnePassLongNotPrefix-12             405ns ± 0%     410ns ± 0%   +1.23%  (p=0.000 n=8+9)
MatchParallelShared-12              501ns ± 1%      39ns ± 1%  -92.27%  (p=0.000 n=10+10)
MatchParallelCopied-12             39.1ns ± 0%    39.2ns ± 3%     ~     (p=0.785 n=6+10)
QuoteMetaAll-12                    94.6ns ± 0%    94.6ns ± 0%     ~     (p=0.439 n=10+8)
QuoteMetaNone-12                   52.7ns ± 0%    52.7ns ± 0%     ~     (all equal)
Match/Easy0/32-12                  79.1ns ± 0%    72.9ns ± 0%   -7.85%  (p=0.000 n=9+9)
Match/Easy0/1K-12                   307ns ± 1%     298ns ± 0%   -2.99%  (p=0.000 n=10+6)
Match/Easy0/32K-12                 4.65µs ± 2%    4.60µs ± 2%     ~     (p=0.159 n=10+10)
Match/Easy0/1M-12                   234µs ± 0%     235µs ± 0%   +0.17%  (p=0.003 n=10+10)
Match/Easy0/32M-12                 7.98ms ± 1%    7.96ms ± 0%     ~     (p=0.278 n=9+10)
Match/Easy0i/32-12                 1.13µs ± 1%    1.09µs ± 0%   -3.24%  (p=0.000 n=9+8)
Match/Easy0i/1K-12                 32.5µs ± 0%    31.7µs ± 0%   -2.66%  (p=0.000 n=9+9)
Match/Easy0i/32K-12                1.59ms ± 0%    1.61ms ± 0%   +0.75%  (p=0.000 n=9+9)
Match/Easy0i/1M-12                 51.0ms ± 0%    51.4ms ± 0%   +0.77%  (p=0.000 n=10+8)
Match/Easy0i/32M-12                 1.63s ± 0%     1.65s ± 1%   +1.24%  (p=0.000 n=7+9)
Match/Easy1/32-12                  75.1ns ± 1%    67.9ns ± 0%   -9.54%  (p=0.000 n=8+8)
Match/Easy1/1K-12                   861ns ± 0%     884ns ± 0%   +2.71%  (p=0.000 n=8+9)
Match/Easy1/32K-12                 39.2µs ± 1%    39.2µs ± 0%     ~     (p=0.090 n=10+9)
Match/Easy1/1M-12                  1.38ms ± 0%    1.39ms ± 0%     ~     (p=0.095 n=10+9)
Match/Easy1/32M-12                 44.2ms ± 1%    44.2ms ± 1%     ~     (p=0.218 n=10+10)
Match/Medium/32-12                 1.04µs ± 1%    1.05µs ± 0%   +1.05%  (p=0.000 n=9+8)
Match/Medium/1K-12                 31.3µs ± 0%    31.3µs ± 0%   -0.14%  (p=0.004 n=9+9)
Match/Medium/32K-12                1.44ms ± 0%    1.45ms ± 0%   +0.18%  (p=0.001 n=8+8)
Match/Medium/1M-12                 46.1ms ± 0%    46.2ms ± 0%   +0.13%  (p=0.003 n=6+9)
Match/Medium/32M-12                 1.48s ± 0%     1.48s ± 0%   +0.20%  (p=0.002 n=9+8)
Match/Hard/32-12                   1.54µs ± 1%    1.49µs ± 0%   -3.60%  (p=0.000 n=9+10)
Match/Hard/1K-12                   46.4µs ± 1%    45.1µs ± 1%   -2.78%  (p=0.000 n=9+10)
Match/Hard/32K-12                  2.19ms ± 0%    2.18ms ± 1%   -0.51%  (p=0.006 n=8+9)
Match/Hard/1M-12                   70.1ms ± 0%    69.7ms ± 1%   -0.52%  (p=0.006 n=8+9)
Match/Hard/32M-12                   2.24s ± 0%     2.23s ± 1%   -0.42%  (p=0.046 n=8+9)
Match/Hard1/32-12                  8.17µs ± 1%    7.89µs ± 0%   -3.42%  (p=0.000 n=8+9)
Match/Hard1/1K-12                   254µs ± 2%     244µs ± 0%   -3.91%  (p=0.000 n=9+9)
Match/Hard1/32K-12                 9.58ms ± 1%   10.35ms ± 0%   +8.00%  (p=0.000 n=10+10)
Match/Hard1/1M-12                   306ms ± 1%     331ms ± 0%   +8.27%  (p=0.000 n=9+8)
Match/Hard1/32M-12                  9.79s ± 1%    10.60s ± 0%   +8.29%  (p=0.000 n=9+8)
Match_onepass_regex/32-12           808ns ± 0%     812ns ± 0%   +0.47%  (p=0.000 n=8+10)
Match_onepass_regex/1K-12          27.8µs ± 0%    28.5µs ± 0%   +2.32%  (p=0.000 n=8+10)
Match_onepass_regex/32K-12          925µs ± 0%     936µs ± 0%   +1.24%  (p=0.000 n=9+10)
Match_onepass_regex/1M-12          29.5ms ± 0%    30.2ms ± 0%   +2.38%  (p=0.000 n=10+10)
Match_onepass_regex/32M-12          945ms ± 0%     970ms ± 0%   +2.60%  (p=0.000 n=9+10)
CompileOnepass-12                  4.67µs ± 0%    4.63µs ± 1%   -0.84%  (p=0.000 n=10+10)
[Geo mean]                         24.5µs         23.3µs        -5.04%

https://perf.golang.org/search?q=upload:20181004.1

Change-Id: Idbc2b76223718265657819ff38be2d9aba1c54b4
Reviewed-on: https://go-review.googlesource.com/c/139779
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>