feat(hugr-passes)!: normalize_cfgs inlines entry DFG

[acl-cqc]

Breaking followup to #2633.

• normalize_cfgs moves the entry block outside the CFG even if there are outgoing Dom edges by inlining the DFG (so the entry block children become siblings of the CFG), as this makes said edges into valid Ext edges.

Sadly, I don't see a good/corresponding treatment for the exit dfg; it doesn't help that the source block of the Dom edges must dominate the exit (and hence we could break the CFG just before that source block and start another CFG), because even then there could be backedges to the source (new CFG entry) block, so we can't necessarily lift it outside. Options thus seem to be:

1. thread the values from the source block through the whole CFG
2. add extra outputs to the CFG, and thus to each predecessor of the new exit block - but that requires either finding the corresponding Tag, or also adding new inputs to any other successors of those predecessors (and any other predecessors of those, and so on)

...and I've not tried either of those here.

BREAKING CHANGE: NormalizeCFGResult specifies entry_nodes_moved not entry_dfg (as no DFG is inserted).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.46%. Comparing base (5e354b9) to head (94d2c75).
⚠️ Report is 16 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2649   +/-   ##
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  Coverage   83.46%   83.46%           
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  Files         262      262           
  Lines       51297    51297           
  Branches    46858    46858           
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+ Hits        42813    42815    +2     
+ Misses       6105     6103    -2     
  Partials     2379     2379           

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[hugrbot]

This PR contains breaking changes to the public Rust API.

cargo-semver-checks summary

    Building hugr v0.24.3 (current)
     Built [  18.801s] (current)
   Parsing hugr v0.24.3 (current)
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  Building hugr v0.24.3 (baseline)
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  Checking hugr v0.24.3 -> v0.24.3 (assume minor change)
   Checked [   0.011s] 159 checks: 159 pass, 41 skip
   Summary no semver update required
  Finished [  37.727s] hugr
  Building hugr-cli v0.24.3 (current)
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  Finished [  36.261s] hugr-cli
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  Building hugr-model v0.24.3 (current)
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   Parsing hugr-model v0.24.3 (current)
    Parsed [   0.015s] (current)
  Building hugr-model v0.24.3 (baseline)
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   Parsing hugr-model v0.24.3 (baseline)
    Parsed [   0.014s] (baseline)
  Checking hugr-model v0.24.3 -> v0.24.3 (assume minor change)
   Checked [   0.025s] 159 checks: 159 pass, 41 skip
   Summary no semver update required
  Finished [   9.999s] hugr-model
  Building hugr-passes v0.24.3 (current)
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   Parsing hugr-passes v0.24.3 (current)
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   Parsing hugr-passes v0.24.3 (baseline)
    Parsed [   0.023s] (baseline)
  Checking hugr-passes v0.24.3 -> v0.24.3 (assume minor change)
   Checked [   0.028s] 159 checks: 157 pass, 2 fail, 0 warn, 41 skip

--- failure enum_struct_variant_field_added: pub enum struct variant field added ---

Description:
An enum's exhaustive struct variant has a new field, which has to be included when constructing or matching on this variant.
      ref: https://doc.rust-lang.org/reference/attributes/type_system.html#the-non_exhaustive-attribute
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.45.0/src/lints/enum_struct_variant_field_added.ron

Failed in:
field entry_nodes_moved of variant NormalizeCFGResult::CFGPreserved in /home/runner/work/hugr/hugr/PR_BRANCH/hugr-passes/src/normalize_cfgs.rs:89

--- failure enum_struct_variant_field_missing: pub enum struct variant's field removed or renamed ---

Description:
A publicly-visible enum has a struct variant whose field is no longer available under its prior name. It may have been renamed or removed entirely.
      ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
     impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.45.0/src/lints/enum_struct_variant_field_missing.ron

Failed in:
field entry_dfg of variant NormalizeCFGResult::CFGPreserved, previously in file /home/runner/work/hugr/hugr/BASELINE_BRANCH/hugr-passes/src/normalize_cfgs.rs:88

   Summary semver requires new major version: 2 major and 0 minor checks failed
  Finished [  27.990s] hugr-passes
  Building hugr-persistent v0.3.4 (current)
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   Parsing hugr-persistent v0.3.4 (current)
    Parsed [   0.007s] (current)
  Building hugr-persistent v0.3.4 (baseline)
     Built [  10.627s] (baseline)
   Parsing hugr-persistent v0.3.4 (baseline)
    Parsed [   0.007s] (baseline)
  Checking hugr-persistent v0.3.4 -> v0.3.4 (assume minor change)
   Checked [   0.011s] 159 checks: 159 pass, 41 skip
   Summary no semver update required
  Finished [  22.350s] hugr-persistent

[acl-cqc]

@croyzor I picked you because you were randomly picked for #2662 after Seyon had already stepped in, so remembering the lost roll of the dice ;)

[croyzor]

wont this capture the input/output nodes?

[acl-cqc]

Yes - we've built a DFG node, but not using the "builder", so it's completely empty; we transfer Input and Output nodes into it to make it valid. Then we do an InlineDFG, which removes them.