[PATCH] D46493: [DagCombiner] Not all 'andn''s work with immediates.

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In https://reviews.llvm.org/D46493#1089126, @andreadb wrote:

> In https://reviews.llvm.org/D46493#1089104, @lebedev.ri wrote:
>
> > In https://reviews.llvm.org/D46493#1089097, @andreadb wrote:
> >
> > > > I'd say this regression is an improvement, since IPC increased in that case?
> > >
> > > As a rule of thumb when using llvm-mca, it's best to always remove return statements from the assembly code sequence.
> > >  llvm-mca should have warned you about the presence of a return statement in the input sequence:
> > >
> > >   warning: found a return instruction in the input assembly sequence.
> > >   note: program counter updates are ignored.
> > >
> > >
> > > To get the correct resource pressure distribution in example icmp-opt.txt, you should remove the `retq`.
> >
> >
> > Thank you for your comments!
> >  I will filter it out, so hopefully in future my mca expirience will be better :)
> >
> > In https://reviews.llvm.org/D46493#1089097, @andreadb wrote:
> >
> > > If you run multiple iterations and print the timeline view, you can see how the "average wait time" in the scheduler's queue is quite high for the shlq instruction.
> >
> >
> > Aha, so far i kinda ignored `-timeline` switch.
> >  Those flags need work i think. I have just tried enabling them all, and it seems like they invert the current state?
> >  I'd like to 1. have a switch to turn them all on, 2. maybe print which ones are currently enabled in `-help`
>
>
> That should not happen.
>  I guess you passed flag -instruction-tables too? To avoid confusions, I will remove that flag from the "View Options", since it is used to print a completely different report.


Sounds about right.

>   I'd like to 1. have a switch to turn them all on,
>    
>    
> 
> Sure, that can be added.
> 
> 2. maybe print which ones are currently enabled in `-help`
> 
> That can be done. At the moment, the llvm-mca commandline documentation specifies which views are enabled by default. I am going to add that information to the "help" too.

Yay! Thank you!

> Cheers,
> -Andrea




Repository:
  rL LLVM

https://reviews.llvm.org/D46493