[LLVMdev] Requiring dynamically loaded passes

Gordon Henriksen gordonhenriksen at mac.com
Tue Dec 4 08:58:00 PST 2007

On Dec 4, 2007, at 11:24, Vikram S. Adve wrote:

> Is it possible to AddRequired<...> a pass that is dynamically  
> loaded?  This would be very convenient for a course project but the  
> documentation about pass interactions says nothing about dynamically  
> loaded passes and vice versa.
> More specifically, to refer to the pass name in AddRequired, I need  
> to declare it first but then I can't think of a way to load the  
> module implementing the pass dynamically instead of linking it  
> statically.

I think if you define the pass ID in your host and use AddRequiredID  
instead of AddRequired:

     char LoadablePassID = 0;
     AU.addRequiredID(lookupPassInfo((intptr_t) &LoadablePassID));

then it should work if the loadable module references the same pass ID  
as an extern:

     extern char ExternalPassID;

     class ThePass : public ImmutablePass {
       ThePass : ImmutablePass(&ExternalPassID) {}

An analysis group may also be a viable option.

— Gordon

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