[polly] r229252 - Overaproximate divisions in for the alias checks.

[Tobias Grosser]

On 14.02.2015 17:26, Johannes Doerfert wrote:
> On 02/14, Tobias Grosser wrote:
>> On 14.02.2015 13:00, Johannes Doerfert wrote:
>>> Author: jdoerfert
>>> Date: Sat Feb 14 06:00:06 2015
>>> New Revision: 229252
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=229252&view=rev
>>> Log:
>>> Overaproximate divisions in for the alias checks.
>>>
>>>    Alias checks might become costly if there are divisions that complicate the
>>>    description of the accessed locations. By overaproximating them we get fairly
>>>    accurate results without the huge compile time cost.
>>
>> A test case would be nice here.
> I don't have a test case at the moment but I'll try to get one. The idea
> is that we want to check ranges anyway and alias check creation times
> out on lnt since we allowed signed divisions.

I see. If you don't have a test case, please state in the commit message 
why there is none and if you intend to add one later. Otherwise, I will 
keep asking. ;)


>> Also, can you explain why this approximation is always save?
> The isl manual states that the result is an overapproximation. I will
> add a comment to the code.

Right, it indeed seems save. A comment is probably still useful.

Cheers,
Tobias

PS: It seems this patch made the LNT buildbots green again. Nice!