[polly] reorganize scop detection for faster compiles

[Tobias Grosser]

On 06/01/2013 09:31 PM, Sebastian Pop wrote:
> Hi Tobi,
>
> Here are two patches that reorganize scop detection filters: the idea behind these
> patches is to run the lightweight passes accessing the CFG and LoopInfo before
> starting iterating over instructions in basic blocks.
>
> With these and previous patches, we still have room for improvement: here is
> what I still see in one of the files:
>
> Ok to commit?


I don't think they will hurt correctness wise.

However, if you see compile time improvements with these patches, it 
would be nice to know on which benchmarks you see how much improvements. 
Also, do you see any compile-time regressions?

I can see that the patches may reduce compile time for cases where the 
CFG commonly breaks the scops. On the other side, in case the CFGs are 
perfectly well structured, this may actually have a negative effect. I 
tend to agree that the first one may be more common, but it would be 
nice to back this up this intuition with some data.

 > 285.8400 ( 69.2%)   2.1700 ( 44.7%)  288.0100 ( 68.9%)  295.9582 ( 
67.8%)  Polly - Detect static control parts (SCoPs)

Interesting. Do you happen to have a test case for this .ll file, which 
you could create a bug report for?

Cheers,
Tobias