llvm dev - Nov 2010 - [LLVMdev] Question regarding the alias analysis chaining behaviour

On Thu, Nov 25, 2010 at 3:05 PM, Nick Lewycky <nicholas at mxc.ca>
wrote:
> Kenneth Uildriks wrote:
>>
>> On Wed, Nov 24, 2010 at 2:50 PM, Nick Lewycky<nicholas at mxc.ca>
 wrote:
>>
>> I thought analysis passes just rebuilt their state after they got
>> invalidated.  Shouldn't that happen with an AA pass as well?  Or is
AA
>> special?
>
> What makes AA special is that it's in an AnalysisGroup. Yes analyses
will be
> recreated when required by the running pass, but in this case the passes
> require "anything in the AA group" and by default the PassManager
will
> satisfy that by creating BasicAA, not the pass you just wrote and stuck in
> the optz'n list at some point. If you insert an AA pass at some point
then
> the pass manager will return that one until it's invalidated, but will
> create BasicAA next time.
>
> Nick
>
So the trouble is in the way AnalysisGroups are handled, then?  Is
there a desire or plan to change it so that the pass continues to
exist even when it's invalidated and needs to be recomputed?

Hi Kenneth,
> So the trouble is in the way AnalysisGroups are handled, then?  Is
> there a desire or plan to change it so that the pass continues to
> exist even when it's invalidated and needs to be recomputed?
This is definitely a bug which needs to be fixed. Noone just expressed
the willingness to fix it :)

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University

On Fri, Nov 26, 2010 at 3:35 PM, Anton Korobeynikov
<anton at korobeynikov.info> wrote:
> Hi Kenneth,
>
>> So the trouble is in the way AnalysisGroups are handled, then?  Is
>> there a desire or plan to change it so that the pass continues to
>> exist even when it's invalidated and needs to be recomputed?
> This is definitely a bug which needs to be fixed. Noone just expressed
> the willingness to fix it :)
I'll take a look at it over the weekend.