[tree-ssa] POOMA compile time / memory requirement comparison

[Steven Bosscher]

On May 04, 2004 12:22 PM, Richard Guenther <rguenth@tat.physik.uni-tuebingen.de> wrote:

> Here is more data for the merge-criteria of tree-ssa compared to mainline.
> I compiled the tramp-v3.cpp testcase on a 1GB ram ia32 machine with
> gcc-3.5 (GCC) 3.5.0 20040430 (experimental)
> and
> gcc-ssa (GCC) 3.5-tree-ssa 20040504 (merged 20040428)
> with leafify attribute disabled and enabled.
> 
> The summary is
>                 mem     user    sys     wall
> 3.5             387MB   168.98  3.85    181.07
> 3.5 w/leafify   452MB   266.71  4.37    284.90
> ssa             493MB   226.71  5.35    245.18
> ssa w/leafify   575MB   377.43  8.16    412.24
> 
> So tree-ssa memory requirement is 127% of mainline, compile time
> is 134% of mainline (without leafify) and 126% of mainline (with leafify).

I still think this merge requirement is simply unreasonable.  There are RTL optimizers
that we know to be comile time consumers, and which are totally ineffective on
tree-ssa.  For example jump threading, big parts of GCSE, and big chunks of CSE.
Disable those, and then see how tree-ssa compile and execution times compare
to mainline.

I don't know enough about the RTL part of the middle end, but I do know that
there are some things hidden behind flag_expensive_optimizations that increase
memory usage, but have not a whole lot of effect either, with tree-ssa enabled.
Obviously there's still work to be done to decrease the amount of memory that
tree-ssa needs.

How did you measure these memory requirements?

> Details (from the first entries you see, mainline is better at optimizing gcc than tree-ssa):

Where do you see that? 

Gr.
Steven