[LLVMdev] Question regarding the alias analysis chaining behaviour

[Kenneth Uildriks]

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?