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

[Richard Guenther]

Steven Bosscher wrote:
> On Wednesday 05 May 2004 20:41, Richard Guenther wrote:
> 
>>Using the suggested -fno-gcse -fno-cse-follow-jumps -fno-cse-skip-blocks
>>-fno-web, -O2 compilation times improve about 8%.  This leaves us with
> 
> 
> Why not -fno-delete-null-pointer-checks?  And -fweb is enabled on mainline
> and helps tree-ssa iirc, so that should really stay enabled...

-fno-delete-null-pointer-checks doesn't help.  It seems to be cheap.

I thought we have life-splitting enabled in the expander now - so web 
seemed unnecessary.

>>10% to improve elsewhere (I guess, f.i. preserving the CFG could help,
>>as well as removing some first invocations of CSE).
> 
> 
> As well as disabling some stuff hidden behind -fexpensive-optimizations,
> and investigating if we really need to call delete_trivially_dead_insns
> so many times (and iteratively, see cfgcleanup!).  And some other stuff
> like addressof, as discussed here some time ago.  There are still a lot
> of things we have to try...

Yes.  I'm confident we're going to gain more than the current 20% 
regression.  It just needs people remind others about the regressions.

Richard.