[LLVMdev] Choosing an alias analyzer

[Pranav Bhandarkar]

Hi Duncan,

> you have to schedule SCEV alias analysis immediately before your pass.
The
> problem is that if a pass invalidates alias analysis information, then the
next
> time a pass that needs alias analysis is run then the pass manager has to
> recreate alias analysis, and when it does so the SCEV analysis is not
> recreated.  To get around this (which is what is done for TBAA and basic
alias
> analysis if I remember right), the pass needs to be declared immutable,
i.e.
> has no state, so is always valid and doesn't need to be destroyed or
> recreated.
> I doubt this is possible for the SCEV alias analysis, but I didn't look
into it.
> Yes, this is all an endless source of pain.  There's a very old PR about
it
> (PR3703?).
> 
> Ciao, Duncan.
> 
Thanks for the information.

Pranav
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