http://d.puremagic.com/issues/show_bug.cgi?id=2396

           Summary: -O causes very long execution time on foreach loop of
                    large array of structs
           Product: D
           Version: 2.019
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: critical
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: schveiguy@yahoo.com


While porting Tango to D2, I've found the attached file (modified to compile
under phobos) doesn't finish compiling in a reasonable amount of time (a.k.a
never).

The data table is from the Tango locale package, I stripped out the struct only so there isn't any real tango code, just data.

If I compile the file without -O it compiles in 6 seconds, which seems reasonable since it's 600k of data.

If you comment out most of the lines in the table, it compiles quickly.  As you add lines back in, the runtime seems to grow exponentially (not scientifically verified).

This file compiles fine with -O under dmd 1.x, Here's a list of dmd2 compilers that I had on my system to try out:

2.015, 2.016, 2.018: also fails
2.006, 2.007: works

Note that in 2.006 and 2.007, it compiled much quicker with -O (.3 seconds)
than without -O using the compilers that fail (6 seconds)


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http://d.puremagic.com/issues/show_bug.cgi?id=2396





------- Comment #1 from schveiguy@yahoo.com  2008-10-06 14:31 -------
Created an attachment (id=275)
 --> (http://d.puremagic.com/issues/attachment.cgi?id=275&action=view)
file to demonstrate bug


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http://d.puremagic.com/issues/show_bug.cgi?id=2396





------- Comment #2 from schveiguy@yahoo.com  2008-10-06 16:15 -------
BTW, this isn't exactly a blocker for Tango/D2, but in order to get it to work, I have to hand-compile the file, as the build-script uses -O for all Tango files.


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http://d.puremagic.com/issues/show_bug.cgi?id=2396





------- Comment #3 from bugzilla@digitalmars.com  2008-10-07 03:23 -------
Pulling out part of the loop body as a separate function or nested function should work as a workaround.


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http://d.puremagic.com/issues/show_bug.cgi?id=2396


Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |clugdbug@yahoo.com.au


--- Comment #4 from Don <clugdbug@yahoo.com.au> 2011-06-23 03:41:47 PDT ---
On DMD2.053 and later, the literal needs to be declared with 'enum' rather than 'static const' to expose the bug.

It's slow because in this case, there is a single expression consisting of
14013 comma expressions, and several places in the backend use algorithms which
are in O(commadepth ^^ 2).
One of the slowest is accumrd() in gflow.c.

There is also something slow in loopopt(), boolopt() and in builddags().

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yebblies <yebblies@gmail.com> changed:

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                 CC|                            |damianday@hotmail.co.uk


--- Comment #5 from yebblies <yebblies@gmail.com> 2012-02-02 01:26:21 EST ---
*** Issue 6771 has been marked as a duplicate of this issue. ***

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yebblies <yebblies@gmail.com> changed:

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--- Comment #6 from yebblies <yebblies@gmail.com> 2012-02-02 01:26:32 EST ---
*** Issue 5684 has been marked as a duplicate of this issue. ***

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yebblies <yebblies@gmail.com> changed:

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--- Comment #7 from yebblies <yebblies@gmail.com> 2012-02-02 01:26:44 EST ---
*** Issue 6643 has been marked as a duplicate of this issue. ***

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--- Comment #8 from Martin Nowak <code@dawg.eu> 2013-03-12 12:21:56 PDT ---
*** Issue 6771 has been marked as a duplicate of this issue. ***

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