SCF IndexSwitch to nested If-Else

[jiahanxie353]

This transform is meant for dialects that inherently does not have a switch control statement (like Calyx)

[jiahanxie353]

#7669 supports nested if-else control

also referencing calyxir/calyx#1177 and calyxir/calyx#1423 if they are relevant

[rachitnigam]

This needs test programs before we can merge it. Please add some tests and tag me when that's done.

[rachitnigam]

Bumping this again.

[jiahanxie353]

Bumping this again.

Thanks for the reminder, I'll change and push again soon!

[jiahanxie353]

I think I should move to directory lib/Transforms/SwitchToIf.cpp since it's transforming an scf operation to another, not lowering to another dialect?

Also tagging code owners for their opinions @mikeurbach @mortbopet , thanks!

[rachitnigam]

Yeah, I think that sounds like a good idea!

[rachitnigam]

Let's add tests before making @mortbopet or @mikeurbach review this PR...

[jiahanxie353]

bumping this
thank you for reviewing folks

[cgyurgyik]

LGTM, one tiny suggestion.

This transform is meant for dialects that inherently does not have a switch control statement (like Calyx)

Another suggestion: make this a bit more descriptive (and declarative) so readers can more easily capture what's going on, e.g.:

Transforms scf.switch to a series of scf.if statements. This is necessary for dialects that don't support switch statements, e.g., Calyx. An example:

%0 = scf.index_switch %cond -> i32
  case 0 { ... }
  case 1 { ... }
  ...

=>

%c0 = arith.cmpi eq %0, 0
%c1 = arith.cmpi eq %0, 1
%0 = scf.if %c0 {
 ...
} else {
  %1 = scf.if %c1 {
    ...
  } else {
    ...
  }
}

[jiahanxie353]

Thanks, refined the description and code based on your review!