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digitalmars.D.bugs - [Bug 73] New: Functions used to initialize variables are not inlined.

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/bugzilla/show_bug.cgi?id=73

           Summary: Functions used to initialize variables are not inlined.
           Product: D
           Version: 0.150
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: P3
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: godaves yahoo.com


/*
   Compile with -O -inline -release
   This program compares performance of 2 loops, one initializing a
    scope local variable w/ a function and the other not.
   The function used as an initializer is not inlined.
   There is about a 11x difference on my system.
*/

import std.stdio, std.date, std.math;

// local copy of std.math.abs()

int abs(int x)
{
return x >= 0 ? x : -x;
}

void main()
{
    int sum = 0;
    d_time s = getUTCtime();
    for(int i = 0; i < 100_000_000; i++)
    {
        int val = abs(i);
        sum += val - val;
    }
    d_time e = getUTCtime();
    writefln("std.math.abs(): sum= ",sum,", secs = ",(e -
s)/cast(double)TicksPerSecond);

    d_time tmp = e - s;

    sum = 0;
    s = getUTCtime();
    for(int i = 0; i < 100_000_000; i++)
    {
        int val;
        val = abs(i);
        sum += val - val;
    }
    e = getUTCtime();
    writefln("local abs():    sum= ",sum,", secs = ",(e -
s)/cast(double)TicksPerSecond);

    writefln("ratio = ", tmp / cast(double)(e - s));
}


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Mar 24 2006
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/bugzilla/show_bug.cgi?id=73


unknown simplemachines.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |unknown simplemachines.org





There's a comment in inline.c for DeclarationExp's saying:

// Should scan variable initializers

But it isn't happening right now.  Adding a basic scan of the ExpInitializer
(if present) the same way DeclarationExp::inlineCost works seems to resolve
this, but considering how trivial that is... I can't help but expect that
there's more to it than just that.

-[Unknown]


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Mar 25 2006
prev sibling next sibling parent reply d-bugmail puremagic.com writes:
http://d.puremagic.com/bugzilla/show_bug.cgi?id=73








 There's a comment in inline.c for DeclarationExp's saying:
 
 // Should scan variable initializers
 
 But it isn't happening right now.  Adding a basic scan of the ExpInitializer
 (if present) the same way DeclarationExp::inlineCost works seems to resolve
 this, but considering how trivial that is... I can't help but expect that
 there's more to it than just that.
 


I've noticed that too and agree there must be more to it for some cases. But
couldn't that just be re-written by the compiler as two expressions and then
inlined?

int i = foo(); => int i; i = foo(); => doInline();

Are there cases where that wouldn't be semantically identical?

Thanks,
- Dave


 -[Unknown]



--
Mar 25 2006
parent "Walter Bright" <newshound digitalmars.com> writes:
I've got this one solved, too. No need to expend any more effort on it.
Mar 25 2006
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/bugzilla/show_bug.cgi?id=73






Created an attachment (id=8)
 --> (http://d.puremagic.com/bugzilla/attachment.cgi?id=8&action=view)
Add a basic scan to DeclarationExp.

AFAICT, that's exactly what adding a scan in there does.  I'm just compiling
DMD without backend hooks, but I can see with my changes that it now wants to
inline things (by turning on CANINLINE_LOG.)

It's just calling the inline stuff on ExpInitializer's exp, which is probably
an AssignExp or something, which is a BinExp, which then has the CallExp
checked, which then finally gets inlined.

I'm just worried it wasn't added because it might cause fallout.  I don't
really know the code base, so I'm not privy to what fallout might be caused.

Anyway, here's a patch that shows what I changed to enable inlining in these
cases.  If I had the time on my hands, I might try running DStress with this
patch on gdc, to see if it causes any regressions.

-[Unknown]


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Mar 25 2006
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/bugzilla/show_bug.cgi?id=73


deewiant gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED





Fixed in DMD 0.151.


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Apr 03 2006