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It's both simpler and faster to just unconditionally do two 32-bit multiplies rather than a bunch of branching to try to avoid them. This is safe thanks to the tight bounds derived in [1] and verified during mksizeclasses.go. Benchstat results below for compilebench benchmarks on my P920. See also [2] for micro benchmarks comparing the new functions against the originals (as well as several basic attempts at optimizing them). name old time/op new time/op delta Template 295ms ± 3% 290ms ± 1% -1.95% (p=0.000 n=20+20) Unicode 113ms ± 3% 110ms ± 2% -2.32% (p=0.000 n=21+17) GoTypes 1.78s ± 1% 1.76s ± 1% -1.23% (p=0.000 n=21+20) Compiler 119ms ± 2% 117ms ± 4% -1.53% (p=0.007 n=20+20) SSA 14.3s ± 1% 13.8s ± 1% -3.12% (p=0.000 n=17+20) Flate 173ms ± 2% 170ms ± 1% -1.64% (p=0.000 n=20+19) GoParser 278ms ± 2% 273ms ± 2% -1.92% (p=0.000 n=20+19) Reflect 686ms ± 3% 671ms ± 3% -2.18% (p=0.000 n=19+20) Tar 255ms ± 2% 248ms ± 2% -2.90% (p=0.000 n=20+20) XML 335ms ± 3% 327ms ± 2% -2.34% (p=0.000 n=20+20) LinkCompiler 799ms ± 1% 799ms ± 1% ~ (p=0.925 n=20+20) ExternalLinkCompiler 1.90s ± 1% 1.90s ± 0% ~ (p=0.327 n=20+20) LinkWithoutDebugCompiler 385ms ± 1% 386ms ± 1% ~ (p=0.251 n=18+20) [Geo mean] 512ms 504ms -1.61% name old user-time/op new user-time/op delta Template 286ms ± 4% 282ms ± 4% -1.42% (p=0.025 n=21+20) Unicode 104ms ± 9% 102ms ±14% ~ (p=0.294 n=21+20) GoTypes 1.75s ± 3% 1.72s ± 2% -1.36% (p=0.000 n=21+20) Compiler 109ms ±11% 108ms ± 8% ~ (p=0.187 n=21+19) SSA 14.0s ± 1% 13.5s ± 2% -3.25% (p=0.000 n=16+20) Flate 166ms ± 4% 164ms ± 4% -1.34% (p=0.032 n=19+19) GoParser 268ms ± 4% 263ms ± 4% -1.71% (p=0.011 n=18+20) Reflect 666ms ± 3% 654ms ± 4% -1.77% (p=0.002 n=18+20) Tar 245ms ± 5% 236ms ± 6% -3.34% (p=0.000 n=20+20) XML 320ms ± 4% 314ms ± 3% -2.01% (p=0.001 n=19+18) LinkCompiler 744ms ± 4% 747ms ± 3% ~ (p=0.627 n=20+19) ExternalLinkCompiler 1.71s ± 3% 1.72s ± 2% ~ (p=0.149 n=20+20) LinkWithoutDebugCompiler 345ms ± 6% 342ms ± 8% ~ (p=0.355 n=20+20) [Geo mean] 484ms 477ms -1.50% [1] Daniel Lemire, Owen Kaser, Nathan Kurz. 2019. "Faster Remainder by Direct Computation: Applications to Compilers and Software Libraries." https://arxiv.org/abs/1902.01961 [2] https://github.com/mdempsky/benchdivmagic Change-Id: Ie4d214e7a908b0d979c878f2d404bd56bdf374f6 Reviewed-on: https://go-review.googlesource.com/c/go/+/300994 Run-TryBot: Matthew Dempsky <mdempsky@google.com> Trust: Matthew Dempsky <mdempsky@google.com> Trust: Michael Knyszek <mknyszek@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Michael Knyszek <mknyszek@google.com> |
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