[LLVMdev] Complex load patterns and token factors

[Hal Finkel]

On Sun, 24 Jun 2012 18:09:48 +0100
Tim Northover <t.p.northover at gmail.com> wrote:

> > If it is not being used, maybe we should change it to be
> > doesNotNeedChain?
> 
> That sounded like a really good idea until I started to actually go
> through removing all traces of hasCtrlDep from other Targets. I felt
> really bad about wiping those flags people had carefully put on their
> instructions, even if useless.
> 
> > I am not sure what kind of load does not need to be chained
> > (prefetch?), but I'd prefer to keep the system friendly if at all
> > possible. They'll be fewer bugs that way.
> 
> That is the main worry. Could we justify a second "hasNoCtrlDep" in
> addition to "hasCtrlDep", with it being a TableGen error to set both?
> Or just forget about the override until someone actually comes up with
> an instruction that's legitimately "mayLoad" or whatever yet doesn't
> want a chain

This is probably the best approach. There is no need to invent a
feature with no use cases.

 -Hal

> (I don't think even prefetch counts -- if other
> instructions are modifying that location it needs to know).
> 
> > Thanks again,
> 
> No worries.
> 
> Tim.



-- 
Hal Finkel
Postdoctoral Appointee
Leadership Computing Facility
Argonne National Laboratory