Update canonicalization of cc.if

[atgeller]

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[github-actions]

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[sacpis]

Overall LGTM. Thanks @atgeller. Left a comment.

[sacpis]

If we fold a multi exit cc.if inside a loop's while or step region it produces invalid IR and the canonicalizer errors out.

I tried running cudaq-opt -canonicalize on the following mlir

func.func private @side() -> i1
func.func @in_while(%arg: i1) {
  %c = arith.constant true
  cc.loop while {
    cc.if (%c) {
      cf.cond_br %arg, ^bb1, ^bb2
    ^bb1:
      %z = func.call @side() : () -> i1
      cc.continue
    ^bb2:
      cc.continue
    }
    %p = func.call @side() : () -> i1
    cc.condition %p
  } do {
    %y = func.call @side() : () -> i1
    cc.continue
  }
  return
}

It gives me the error as

error: 'cc.loop' op region #0 ('whileRegion') failed to verify constraint: region with 1 blocks

I think before taking the multi exit path, we should bail out when the region holding the cc.if cannot take extra blocks. The single block path do not need such a guard.

[schweitzpgi]

Thanks for the renovations. A couple of quick comments.

[schweitzpgi]

Let's use cudaq::opt::factory::maybeValueOfIntConstant

[schweitzpgi]

Can we splice the entire region, rewrite the cc.continue operations to cf.br to a new block with block arguments and then rewrite all uses of the cc.if values to use those block arguments? That should handle the CFG inside the then/else region cases.

It should be the same, effectively, as what lower-to-cfg does. MIght be a refactor opportunity?

[schweitzpgi]

Good idea.