[PATCH] D13257: [LAA] LLE 4/6: APIs to access the dependent instructions for a dependence, NFC

[Hal Finkel via llvm-commits]

hfinkel added a comment.

In http://reviews.llvm.org/D13257#330229, @anemet wrote:

> In http://reviews.llvm.org/D13257#279151, @hfinkel wrote:
>
> > Maybe I'm overlooking some existing commentary, but we should do a better job of documenting what the source and destination mean where there are multiple possible sources and/or destinations of the same distance. To be clear about what I mean, if I take your example from http://reviews.llvm.org/D13254:
> >
> >   for (unsigned i = 0; i < 100; i++) {
> >     A[i+8] = B[i] + 2;
> >     C[i] = A[i] * 2;
> >   }
> >   
> >
> > and I do this:
> >
> >   for (unsigned i = 0; i < 100; i++) {
> >     A[i+8] = B[i] + 2;
> >     A[i+8] = F[i] + 2;
> >     C[i] = A[i] * 2;
> >     D[i] = A[i] * 4;
> >   }
> >   
> >
> > are there multiple distance-8 dependencies, or only one for A[i] <-> A[i+8], and if only one, to which A[i+8] store does it refer (the first or the second). I realize this is a bit silly here, because one of these stores is dead, but generally speaking, we should define how this is represented.
>
>
> Hal, sorry for the huge delay on this but now that I got back to this and reread your question, I think I understand the disconnect.  Dependence objects are between instructions and *not* between pointers/accesses.  (This is one change when LAA was moved out of LV and the interface was generalized.) Thus we will have multiple distance-8 dependence here as I said in my original reply.
>
> There is a comment before the Dependence class mentioning that this is a relation between instructions (and not pointers/accesses):
>
>   /// \brief Dependece between memory access instructions.
>   struct Dependence {
>   
>
> Let me know if that's sufficient or you want me to elaborate somehow.


I think that's sufficient. Thanks for following-up.

> Thanks,

> Adam





Repository:
  rL LLVM

http://reviews.llvm.org/D13257