[llvm-dev] LV: predication

[David Greene via llvm-dev]

Sjoerd Meijer via llvm-dev <llvm-dev at lists.llvm.org> writes:

> This is what we are currently doing and works excellent for simpler
> cases. For the more complicated cases that we now what to handle as
> well, the pattern matching just becomes a bit too horrible, and it is
> fragile too. All we need is the information that the vectoriser
> already has, and pass this on somehow.
>
> As I am really keen to simply our backend pass, would there be another
> way to pass this information on? If emitting an intrinsic is a
> blocker, could this be done with a loop annotation?

I have had to communicate information exactly like this from optimizer
to late codegen.  It is painful and would be a lot easier if we had
metadata support in machine instructions.  Perhaps that is an avenue to
pursue as it would be more general and applicable to lots of things.

                   -David