Re: [tree-ssa] Merge status

[Richard Guenther <rguenth at tat dot physik dot uni-tuebingen dot de>]

Gerald Pfeifer wrote:
> On Sat, 13 Mar 2004, Richard Guenther wrote:
>
> > Yes, I suspect for a start we can move some optimizations from -O2 to
> > -O3 to improve -O2 compile time.
>
>
> Now, that's cheating, isn't it?  This is acceptable if and only if it
> really never hurts runtime performance, but then I don't see the benefit
> of such optimizations at all!

Of course it is cheating ;)  But there may be architectures that need a 
lot CSE/GCSE cleanup from their rtl patterns?  Also one could certainly 
find testcases where f.i. gcse does something useful, so entirely 
removing it is not going to happen soon - moving it to -O3 or even 
removing it from any -On might be prefferable.

F.i. I preffer -fpeel-loops over -funroll-loops to trigger complete 
peeling of constant times running loops - it's actually faster.  But 
-fpeel-loops and -funroll-loops are not enabled at any -On level.

With tree-ssa revisiting of -On enabled options is certainly necessary 
and possibly profitable.  Like maybe making -O default, not -O0 (usually 
-O0 compile times are worse than -O1 for me).

Richard.