http://d.puremagic.com/issues/show_bug.cgi?id=9477

           Summary: String (and array) comparisons are needlessly very
                    slow
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: performance
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: thecybershadow@gmail.com


--- Comment #0 from Vladimir Panteleev <thecybershadow@gmail.com> 2013-02-08 11:18:10 EET ---
While profiling one of my programs, I've noticed a performance issue in an area that I wouldn't expect to be slow: string comparisons.

It looks like array comparisons go through the rather convoluted TypeInfo equality code, which contains a few indirect calls and calls to runtime code. It can be inlined/optimized to a length comparison and a memcmp call.

If the length is known (static arrays), the length check can be skipped, and for short arrays the comparison can even be inlined. Bearophile previously reported this problem for static arrays in issue 6658.

I should note that a slice copy currently compiles to a memcpy call.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
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--- Comment #1 from Walter Bright <bugzilla@digitalmars.com> 2013-03-31 00:59:25 PDT ---
https://github.com/D-Programming-Language/dmd/pull/1766

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--- Comment #2 from github-bugzilla@puremagic.com 2013-03-31 01:02:10 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/c984175cf25dfa17b3956e8e33ff83547fa56b0a Optimize simple array comparison (Issue 9477)

https://github.com/D-Programming-Language/dmd/commit/8b9d88d19fe4bb239209c004230fd5ac271436c3 Merge pull request #1766 from CyberShadow/fix9477

Optimize simple array comparisons (Issue 9477)

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bearophile_hugs@eml.cc changed:

           What    |Removed                     |Added
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                 CC|                            |bearophile_hugs@eml.cc


--- Comment #3 from bearophile_hugs@eml.cc 2013-04-01 14:55:13 PDT ---
See also Issue 6658

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