regexp: reduce allocations at onePassCopy
It reduces needless allocations on compiling onepass regex. name old time/op new time/op delta CompileOnepass/^(?:(?:(?:.(?:$))?))...-4 6.31µs ± 3% 6.11µs ± 3% ~ (p=0.056 n=5+5) CompileOnepass/^abcd$-4 5.69µs ±12% 4.93µs ± 4% -13.42% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a{0,})*?)$-4 7.10µs ±12% 5.82µs ± 5% -17.95% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a+)*)$-4 5.99µs ±10% 6.07µs ±11% ~ (p=1.000 n=5+5) CompileOnepass/^(?:(?:a|(?:aa)))$-4 7.36µs ± 4% 7.81µs ±19% ~ (p=0.310 n=5+5) CompileOnepass/^(?:[^\s\S])$-4 4.71µs ± 3% 4.71µs ± 5% ~ (p=1.000 n=5+5) CompileOnepass/^(?:(?:(?:a*)+))$-4 6.06µs ± 2% 6.23µs ± 9% ~ (p=0.310 n=5+5) CompileOnepass/^[a-c]+$-4 4.74µs ± 4% 4.64µs ± 6% ~ (p=0.421 n=5+5) CompileOnepass/^[a-c]*$-4 5.17µs ± 2% 4.68µs ± 0% -9.57% (p=0.016 n=5+4) CompileOnepass/^(?:a*)$-4 5.34µs ± 3% 5.08µs ±12% ~ (p=0.151 n=5+5) CompileOnepass/^(?:(?:aa)|a)$-4 7.24µs ± 5% 7.33µs ±12% ~ (p=0.841 n=5+5) CompileOnepass/^...$-4 5.28µs ± 3% 4.99µs ± 9% ~ (p=0.095 n=5+5) CompileOnepass/^(?:a|(?:aa))$-4 7.20µs ± 4% 7.24µs ±10% ~ (p=0.841 n=5+5) CompileOnepass/^a((b))c$-4 7.99µs ± 3% 7.76µs ± 8% ~ (p=0.151 n=5+5) CompileOnepass/^a.[l-nA-Cg-j]?e$-4 8.30µs ± 5% 7.29µs ± 4% -12.08% (p=0.008 n=5+5) CompileOnepass/^a((b))$-4 7.34µs ± 4% 7.24µs ±19% ~ (p=0.690 n=5+5) CompileOnepass/^a(?:(b)|(c))c$-4 9.80µs ± 6% 9.49µs ±18% ~ (p=0.151 n=5+5) CompileOnepass/^a(?:b|c)$-4 5.23µs ± 3% 4.80µs ±10% ~ (p=0.056 n=5+5) CompileOnepass/^a(?:b?|c)$-4 8.26µs ± 3% 7.30µs ± 3% -11.62% (p=0.008 n=5+5) CompileOnepass/^a(?:b?|c+)$-4 9.18µs ± 2% 8.16µs ± 2% -11.06% (p=0.008 n=5+5) CompileOnepass/^a(?:bc)+$-4 6.16µs ± 3% 6.41µs ±13% ~ (p=0.548 n=5+5) CompileOnepass/^a(?:[bcd])+$-4 5.75µs ± 5% 5.50µs ±12% ~ (p=0.151 n=5+5) CompileOnepass/^a((?:[bcd])+)$-4 7.65µs ± 5% 6.93µs ± 9% ~ (p=0.056 n=5+5) CompileOnepass/^a(:?b|c)*d$-4 13.0µs ± 1% 12.1µs ± 2% -6.91% (p=0.008 n=5+5) CompileOnepass/^.bc(d|e)*$-4 9.20µs ± 4% 8.25µs ± 3% -10.38% (p=0.008 n=5+5) CompileOnepass/^loooooooooooooooooo...-4 254µs ± 2% 220µs ± 6% -13.47% (p=0.008 n=5+5) name old alloc/op new alloc/op delta CompileOnepass/^(?:(?:(?:.(?:$))?))...-4 3.92kB ± 0% 3.41kB ± 0% -13.06% (p=0.008 n=5+5) CompileOnepass/^abcd$-4 3.20kB ± 0% 2.75kB ± 0% -14.00% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a{0,})*?)$-4 3.85kB ± 0% 3.34kB ± 0% -13.31% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a+)*)$-4 3.46kB ± 0% 2.95kB ± 0% -14.78% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a|(?:aa)))$-4 4.20kB ± 0% 3.75kB ± 0% -10.67% (p=0.008 n=5+5) CompileOnepass/^(?:[^\s\S])$-4 3.10kB ± 0% 2.46kB ± 0% -20.62% (p=0.008 n=5+5) CompileOnepass/^(?:(?:(?:a*)+))$-4 3.64kB ± 0% 3.13kB ± 0% -14.07% (p=0.008 n=5+5) CompileOnepass/^[a-c]+$-4 3.06kB ± 0% 2.48kB ± 0% -18.85% (p=0.008 n=5+5) CompileOnepass/^[a-c]*$-4 3.10kB ± 0% 2.52kB ± 0% -18.60% (p=0.008 n=5+5) CompileOnepass/^(?:a*)$-4 3.21kB ± 0% 2.63kB ± 0% -17.96% (p=0.008 n=5+5) CompileOnepass/^(?:(?:aa)|a)$-4 4.09kB ± 0% 3.64kB ± 0% -10.96% (p=0.008 n=5+5) CompileOnepass/^...$-4 3.42kB ± 0% 2.91kB ± 0% -14.95% (p=0.008 n=5+5) CompileOnepass/^(?:a|(?:aa))$-4 4.09kB ± 0% 3.64kB ± 0% -10.96% (p=0.008 n=5+5) CompileOnepass/^a((b))c$-4 5.67kB ± 0% 4.39kB ± 0% -22.59% (p=0.008 n=5+5) CompileOnepass/^a.[l-nA-Cg-j]?e$-4 5.73kB ± 0% 4.32kB ± 0% -24.58% (p=0.008 n=5+5) CompileOnepass/^a((b))$-4 5.41kB ± 0% 4.06kB ± 0% -24.85% (p=0.008 n=5+5) CompileOnepass/^a(?:(b)|(c))c$-4 6.40kB ± 0% 5.31kB ± 0% -17.00% (p=0.008 n=5+5) CompileOnepass/^a(?:b|c)$-4 3.46kB ± 0% 2.88kB ± 0% -16.67% (p=0.008 n=5+5) CompileOnepass/^a(?:b?|c)$-4 5.77kB ± 0% 4.36kB ± 0% -24.41% (p=0.008 n=5+5) CompileOnepass/^a(?:b?|c+)$-4 5.94kB ± 0% 4.59kB ± 0% -22.64% (p=0.008 n=5+5) CompileOnepass/^a(?:bc)+$-4 3.60kB ± 0% 3.15kB ± 0% -12.44% (p=0.008 n=5+5) CompileOnepass/^a(?:[bcd])+$-4 3.46kB ± 0% 2.94kB ± 0% -14.81% (p=0.008 n=5+5) CompileOnepass/^a((?:[bcd])+)$-4 5.50kB ± 0% 4.09kB ± 0% -25.62% (p=0.008 n=5+5) CompileOnepass/^a(:?b|c)*d$-4 7.24kB ± 0% 6.15kB ± 0% -15.03% (p=0.008 n=5+5) CompileOnepass/^.bc(d|e)*$-4 5.75kB ± 0% 4.47kB ± 0% -22.25% (p=0.008 n=5+5) CompileOnepass/^loooooooooooooooooo...-4 225kB ± 0% 135kB ± 0% -39.99% (p=0.008 n=5+5) name old allocs/op new allocs/op delta CompileOnepass/^(?:(?:(?:.(?:$))?))...-4 52.0 ± 0% 49.0 ± 0% -5.77% (p=0.008 n=5+5) CompileOnepass/^abcd$-4 44.0 ± 0% 41.0 ± 0% -6.82% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a{0,})*?)$-4 52.0 ± 0% 49.0 ± 0% -5.77% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a+)*)$-4 47.0 ± 0% 44.0 ± 0% -6.38% (p=0.008 n=5+5) CompileOnepass/^(?:(?:a|(?:aa)))$-4 57.0 ± 0% 54.0 ± 0% -5.26% (p=0.008 n=5+5) CompileOnepass/^(?:[^\s\S])$-4 36.0 ± 0% 33.0 ± 0% -8.33% (p=0.008 n=5+5) CompileOnepass/^(?:(?:(?:a*)+))$-4 49.0 ± 0% 46.0 ± 0% -6.12% (p=0.008 n=5+5) CompileOnepass/^[a-c]+$-4 39.0 ± 0% 36.0 ± 0% -7.69% (p=0.008 n=5+5) CompileOnepass/^[a-c]*$-4 44.0 ± 0% 41.0 ± 0% -6.82% (p=0.008 n=5+5) CompileOnepass/^(?:a*)$-4 45.0 ± 0% 42.0 ± 0% -6.67% (p=0.008 n=5+5) CompileOnepass/^(?:(?:aa)|a)$-4 56.0 ± 0% 53.0 ± 0% -5.36% (p=0.008 n=5+5) CompileOnepass/^...$-4 46.0 ± 0% 43.0 ± 0% -6.52% (p=0.008 n=5+5) CompileOnepass/^(?:a|(?:aa))$-4 56.0 ± 0% 53.0 ± 0% -5.36% (p=0.008 n=5+5) CompileOnepass/^a((b))c$-4 57.0 ± 0% 53.0 ± 0% -7.02% (p=0.008 n=5+5) CompileOnepass/^a.[l-nA-Cg-j]?e$-4 62.0 ± 0% 58.0 ± 0% -6.45% (p=0.008 n=5+5) CompileOnepass/^a((b))$-4 51.0 ± 0% 47.0 ± 0% -7.84% (p=0.008 n=5+5) CompileOnepass/^a(?:(b)|(c))c$-4 69.0 ± 0% 65.0 ± 0% -5.80% (p=0.008 n=5+5) CompileOnepass/^a(?:b|c)$-4 43.0 ± 0% 40.0 ± 0% -6.98% (p=0.008 n=5+5) CompileOnepass/^a(?:b?|c)$-4 61.0 ± 0% 57.0 ± 0% -6.56% (p=0.008 n=5+5) CompileOnepass/^a(?:b?|c+)$-4 67.0 ± 0% 63.0 ± 0% -5.97% (p=0.008 n=5+5) CompileOnepass/^a(?:bc)+$-4 49.0 ± 0% 46.0 ± 0% -6.12% (p=0.008 n=5+5) CompileOnepass/^a(?:[bcd])+$-4 46.0 ± 0% 43.0 ± 0% -6.52% (p=0.008 n=5+5) CompileOnepass/^a((?:[bcd])+)$-4 53.0 ± 0% 49.0 ± 0% -7.55% (p=0.008 n=5+5) CompileOnepass/^a(:?b|c)*d$-4 109 ± 0% 105 ± 0% -3.67% (p=0.008 n=5+5) CompileOnepass/^.bc(d|e)*$-4 66.0 ± 0% 62.0 ± 0% -6.06% (p=0.008 n=5+5) CompileOnepass/^loooooooooooooooooo...-4 1.10k ± 0% 1.09k ± 0% -0.91% (p=0.008 n=5+5) Fixes #19735 Change-Id: Ic68503aaa08e42fafcf7e11cf1f584d674f5ea7b Reviewed-on: https://go-review.googlesource.com/38750Reviewed-by:Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
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