[polly] scop detection: detect regions bottom up

[Sebastian Pop]

Star Tan wrote:
> Hi Sebastian,
> 
> 
> Are you sure that detecting scop regions bottom-up should always lead
> to the same result to detecting scop regions up-down? I think it is based

I think that we should not change the scop detection order.

> on the following assumption:
> Assumption: if a region is a valid scop region, then all of its sub regions must be valid.
> 
> 
> However I find it does not always true. For example, in the attached testcase, the
> outer region "next=>return" is valid, but its sub regioin "for.j => for.inc8" is invalid
> because it is not in simplified loop form. Even if you add "-loop-simplify" to translate
> it to simplified form, the sub region "for.j => for.inc8" is still invalid because the
> region has invalid entering edges.

I agree with your point here: we may have a valid scop composed of smaller
regions that are not valid scops.

Thanks,
Sebastian
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