[LLVMdev] Analysis Passes

[Gordon Henriksen]

On 2008-07-28, at 11:34, Devang Patel wrote:

> On Jul 26, 2008, at 5:56 PM, Gordon Henriksen wrote:
>
>> I had a similar problem with the GC metadata information.  
>> Ultimately, I had to structure it as an ImmutablePass (with an  
>> explicit pass to free the contained information) because it would  
>> be invalidated by other passes at random.
>
> If GC metadata information is not explicitly listed as preserved and  
> the GC metadata pass is not ImmutablePass the, of course, the pass  
> manager will consider the info not available (or dirty) as soon as  
> the pass manager schedules a pass that does not explicitly preserve  
> GC metadata. What else pass manager could do here ?


It's just a different usage case from the 'analysis' concept.  
Requiring that all passes list it as preserved is untenably fragile.

— Gordon