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digitalmars.D.learn - inline functions

reply Caligo <iteronvexor gmail.com> writes:
T[3] data;

T dot(const ref Vector o){
    return data[0] * o.data[0] + data[1] * o.data[1] + data[2] * o.data[2];
}

T LengthSquared_Fast(){ return data[0] * data[0] + data[1] * data[1] +
data[2] * data[2]; }
T LengthSquared_Slow(){ return dot(this); }


The faster LengthSquared() is twice as fast, and I've test with GDC
and DMD.  Is it because the compilers don't inline-expand the dot()
function call?  I need the performance, but the faster version is too
verbose.
Mar 25 2011
parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Fri, 25 Mar 2011 22:04:20 -0400, Caligo <iteronvexor gmail.com> wrote:


 T[3] data;

 T dot(const ref Vector o){
     return data[0] * o.data[0] + data[1] * o.data[1] + data[2] *  
 o.data[2];
 }

 T LengthSquared_Fast(){ return data[0] * data[0] + data[1] * data[1] +
 data[2] * data[2]; }
 T LengthSquared_Slow(){ return dot(this); }


 The faster LengthSquared() is twice as fast, and I've test with GDC
 and DMD.  Is it because the compilers don't inline-expand the dot()
 function call?  I need the performance, but the faster version is too
 verbose.



ref parameters used to make functions not be inlined, but apparently that  
was fixed: http://d.puremagic.com/issues/show_bug.cgi?id=2008

The best thing to do is check the disassembly to see if the call is being  
inlined.

Also, if you want more help besides guessing, a complete working program  
is good to have.

-Steve
Mar 28 2011