[PATCH] D146198: [RISCV] Make ResourceCycles relevant to LMUL

[Wang Pengcheng via Phabricator via llvm-commits]

pcwang-thead added a comment.

In D146198#4202168 <https://reviews.llvm.org/D146198#4202168>, @michaelmaitland wrote:

>> If there are some microarchitectures that can't be modeled, just add a new subroutine to upstream if approved.
>
> Does this mean that subtarget routines must be added to the RISCVScheduleV file since the following function needs to know about the custom subroutine to do its isa checks:
>
>   // Helper class for generating a list of resource cycles of different LMULs.
>   class ResourceCycles<list<ResourceCycle> resourceCycles, string mx> {
>
> I am concerned that the `RISCVScheduleV` file will take on bloat due to holding subtarget related routines if this is the case.

Yes. So I posted this patch here just to discuss how we should handle this.
For example, solutions may be:

1. Add routines to `RISCVScheduleV.td` just as what I have done.
2. Extend `TableGen` to support pass functions:

  // Supposes that we have a Function class to present a function object that its parameters are function parameters.
  class TargetSubroutine<int base, string mx> : Function;
  
  // Then. Supposes that we have a new bang operator to apply this function to input parameters and the result is `ret`.
  class ResourceCycles<list<TargetSubroutine> subroutines, int base, string mx> {
    list<int> value = !foreach(subroutine, subroutines,
                               !apply(subroutine, base, mx)
                              );
  }
  
  // In SchedXXX.td, we can define our own routines.
  class Multiplier<int base, string mx>:TargetSubroutine {
   // We return an int value calculated from mx.
   int ret = !mul(base, multiplier<mx>.value);
  }

3. Some templates are flexible to specify cycles according to LMULs (I haven't figured out one...).


Repository:
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https://reviews.llvm.org/D146198