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()
// (imported functions are not inlined - see DMD bug #67)
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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http://d.puremagic.com/bugzilla/show_bug.cgi?id=73


unknown@simplemachines.org changed:

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




------- Comment #1 from unknown@simplemachines.org  2006-03-25 02:36 -------
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]


-- 

http://d.puremagic.com/bugzilla/show_bug.cgi?id=73





------- Comment #2 from godaves@yahoo.com  2006-03-25 12:01 -------
(In reply to comment #1)
> 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]


-- 

http://d.puremagic.com/bugzilla/show_bug.cgi?id=73





------- Comment #3 from unknown@simplemachines.org  2006-03-25 12:34 -------
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]


-- 

I've got this one solved, too. No need to expend any more effort on it.

http://d.puremagic.com/bugzilla/show_bug.cgi?id=73


deewiant@gmail.com changed:

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




------- Comment #4 from deewiant@gmail.com  2006-04-03 06:09 -------
Fixed in DMD 0.151.


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