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

Sat May 5 08:26:18 PDT 2018

andreadb added a comment.

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.

  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.

Cheers,
-Andrea

Repository:
  rL LLVM

https://reviews.llvm.org/D46493