Compilation performance comparison of 3.5.0 and TreeSSA trees on MICO sources as requested in: [tree-ssa] Merge status 2004-05-03

[Andrew Pinski]

On May 4, 2004, at 17:13, Mike Stump wrote:

> On Tuesday, May 4, 2004, at 01:50 PM, Karel Gardas wrote:
>> MICO doesn't look good. I've compared todays source trees:
>
>> File		350-O0	TSSA-O0	Delta%	350-O2	TSSA-O2
>
>> Sum		523.2	649.36	-19.43	774.7	904.11	-14.31
>>
>> Conclusion: compile time regressions for both -O0 and -O2 compilation.
>
> Thanks.  While I'll happily take the 14% hit for optimized code, the 
> 20% drop for -O0 I want to bitch about.  Last time we lost 34% in one 
> tiny patch, we lost, and the work went in anyway.  That was almost ok, 
> as we just reverted the work that caused the regression in our tree.  
> However, we have no ability to `revert' treessa for -O0 to gain the 
> 20% back.
>
> I'd like ask people to see if there is anyway to get that back.  If 
> not all of it, part of it?

Yes there is a way, it is called do some optimizations at -O0.  The 
problem with the tree-ssa,
the RTL which is generated for an unoptimized run is just huge compared 
to what the mainline
was/is.  Simple things like DCE will help a lot on the compile time and 
code size.

Thanks,
Andrew Pinski