[PATCH] D49243: [X86] Improved sched models for X86 BT*rr instructions

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: lib/Target/X86/X86Schedule.td:122
+// Bit Test
+defm WriteBTr    : X86SchedWritePair;
+
----------------
RKSimon wrote:
> avt77 wrote:
> > lebedev.ri wrote:
> > > RKSimon wrote:
> > > > lebedev.ri wrote:
> > > > > Hmm. Nits:
> > > > > 1. (not a nit) The suffix `r` notes that only the non-mem versions are covered.
> > > > >    I wonder if we can convey that somehow better.
> > > > > 2. These cover 4 different bit-test instructions - `bt`,`bt[rcs]`
> > > > >    Naming this `WriteBTr` //may// be confizing - is this only about `bt` instruction?
> > > > >    How about calling it `WriteBitTest`?
> > > > I'm confused - this should be probably be called WriteBT. But then you've declared this as a X86SchedWritePair but you're not using the folded half of the pair?
> > > Note that it *only* covers `rr` versions, and does not include `mr` versions.
> > > So yeah, maybe it shouldn't be `X86SchedWritePair`, but `X86WriteRes`?
> > I'm going to implement mr version asap that's why I use Pair here.
> If the memory cases are causing a problem it'd be acceptable to just do a reg-reg version for now:
> 
> def  WriteBitTest    : SchedWrite // Bit Test - TODO add memory folding support
> 
> And you can come back to the memory cases once we understand whats to be done. I just don't want a X86SchedWritePair def when you're not using the folded case.
Very minor, but please can you put the WriteBT defs next to the CMOV/SETCC defs - they are closer in behaviour.


https://reviews.llvm.org/D49243