Re: [RFC] Contributing tree-ssa to mainline

[Scott A Crosby <scrosby at cs dot rice dot edu>]

On Fri, 16 Jan 2004 22:09:35 -0800, Andrew Pinski <pinskia@physics.uc.edu> writes:

> >>> people claimed it was "essential" for 3.5 since there was a
> >>> tremendous
> >>> improvement on some C++ cases.  So let's see those cases.
> >>>
> >> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12747
> >

There's also PR2399, where bar is a template based representation of a
16x16x16 array:

void bar (D3VolumeIndex<char,D3VolumeFixed<char,16,16,16> >::Index bar) {
  bar[5][4][3]=10;
}

This compiles to a function using 120 bytes of stack space and 25
mov's. It should be a single instruction.

As this would have been in the inner loops for my analysis package, I
switched idioms rather than benchmark the performance degradation. I
expect it would have been hideous, unless inlining and LCM moved the
useless initialization out of the loops.

Scott