[PATCH] Add support to FileCheck for out-of-order matching

[Robinson, Paul]

> >>> Is it valueable to mix CHECK-NOT and CHECK-DAG together?
> >>
> >> Hal, do you have any use cases where it would be useful to mix
> >> CHECK-DAG and CHECK-NOT?
> >
> > Not currently; if I have CHECK-DAG then I can affirmatively check for
> the instructions that I expect (regardless of order), and I can't think
> of a case where I'd mix that with CHECK-NOT.
> 
> In that case, I think we should go with the simplest possible semantics
> when mixing CHECK-DAG and CHECK-NOT.
> 
> To me, that is having CHECK-NOT act as a barrier, just like CHECK does.
> CHECK-DAGs don't reorder across a CHECK-NOT.

But CHECK-NOT shouldn't match anything and so doesn't define a point
in the output file?  So what does it mean to not reorder across a
point that doesn't exist?

Or did you mean this:
    CHECK-DAG: A
    CHECK-DAG: B
    CHECK-NOT: C
    CHECK-DAG: D
    CHECK-DAG: E
that A/B are unordered wrt each other but both must appear before D/E?
Seems like kind of an obscure usage.
--paulr