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fixed performance regression in endsWith() #331

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fixed performance regression in endsWith() #331

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firewave
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@firewave firewave commented Nov 14, 2023 •
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This regression was introduced in 8abab5c.

std::equal() is supposed to be faster than std::string::compare() and a benchmark even supports this: https://quick-bench.com/q/JkxxUMqC8wLufOw7AUI-l1K-n7Q. But somehow in our code it leads to a big performance regression when using the Clang compiler.

before

Benchmark 1: ./simplecpp -q -D__GNUC__ -D__x86_64__ -DHAVE_CONFIG_H -I ../../xrdp/build ../../xrdp/common/file.c
  Time (mean ± σ):     166.8 ms ±  29.3 ms    [User: 142.4 ms, System: 22.6 ms]
  Range (min … max):   131.9 ms … 218.9 ms    12 runs

after

Benchmark 1: ./simplecpp -q -D__GNUC__ -D__x86_64__ -DHAVE_CONFIG_H -I ../../xrdp/build ../../xrdp/common/file.c
  Time (mean ± σ):      11.5 ms ±   0.6 ms    [User: 9.0 ms, System: 2.6 ms]
  Range (min … max):    10.9 ms …  14.6 ms    216 runs

With GCC this also exists but is much less severe.

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firewave commented May 6, 2024

Strangely I can no longer reproduce the issue.

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