fix: DeadCodeElim keeps consumers of linear outputs #2560

acl-cqc · 2025-09-17T11:53:00Z

Partly addresses #2557 - this would produce a valid Hugr, but still change the result semantics, so more is needed.

Nonetheless this change seems correct in principle.

codecov · 2025-09-17T11:56:23Z

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✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.87%. Comparing base (ef06013) to head (a30f022).
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##             main    #2560      +/-   ##
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+ Hits        39475    39524      +49     
- Misses       6052     6104      +52     
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…alues

hugr-passes/src/dead_code.rs

aborgna-q · 2025-09-17T14:34:07Z

hugr-passes/src/dead_code.rs

+            for (tgt_n, tgt_port) in h.all_linked_inputs(n) {
+                if h.signature(tgt_n)


nit: Query the signature once outside the loop.

Signature of target of edge leaving n, may be different for each edge

Ok, done the other way. This revealed that DCE had been silently skipping any with_entrypoints not in the Hugr (!). I turned that into an assert in e5e8f4c, which required fixing a test, but (a) that's a behaviour change, so should probably be considered breaking; (b) if we do want to do that, should be an actual error, and DeadCodeElimPass has type Error = Infallible, so definitely breaking.

Hence, I've added an explicit check to skip such nodes. If you're ok with that, I'm happy to make an issue/wait-to-merge-PR to turn this into an error for the next breaking release??

Ignoring invalid nodes seems like a safe solution here.

Agreed that this should be turned into an error in a breaking release.
(Make an issue and put it on the next release milestone)

… composable::test_then") This reverts commit 1458537bf197cd9248dc28c48b98ce1f36bcfe10. Skip missing entrypoints

Partly addresses #2557 - this would produce a valid Hugr, but still change the `result` semantics, so more is needed. Nonetheless this change seems correct in principle.

Add test pass runs over the circuits from #904. Some notable issues: - The constant folding pass (and DCE) fails on some cases, leaving unconnected qubit ports. CQCL/hugr#2557 Should be fixed on CQCL/hugr#2560 - (Requires Hugr `0.22.4` / `0.23` release) - The basic-block merge rewrite should define a composable pass. CQCL/hugr#2556 - We are missing a simple `InlineCFG` pass to unwrap simple linear CFGs. (Either single blocks, or it can be conbined with `merge_bbs`). CQCL/hugr#945 If we fix those, we should be able to `assert!` that some of the examples here optimize to the identity. We'll need to call pytket optimisations for the rest. - ~Requires a `hugr 0.22.3` release with this fix: CQCL/hugr#2549 - Requires #1118

…2566) At the moment (before and after #2560) it turns out they were silently dropped. This requires changing the error type of DeadCodeElimPass from Infallible, hence breakage is unavoidable. Might this be a good time to change `with_entry_points` to, oh, `with_start_points` or something that reduces confusion with `HugrView::entrypoint`?? Happy to do that renaming here although haven't done so atm. BREAKING CHANGE: DeadCodeElimPass's implementation of ComposablePass now returns an error (not Infallible)

## 🤖 New release * `hugr-model`: 0.22.4 -> 0.23.0 (✓ API compatible changes) * `hugr-core`: 0.22.4 -> 0.23.0 (⚠ API breaking changes) * `hugr-llvm`: 0.22.4 -> 0.23.0 (✓ API compatible changes) * `hugr-passes`: 0.22.4 -> 0.23.0 (⚠ API breaking changes) * `hugr-persistent`: 0.2.3 -> 0.3.0 (✓ API compatible changes) * `hugr`: 0.22.4 -> 0.23.0 (✓ API compatible changes) * `hugr-cli`: 0.22.4 -> 0.23.0 (✓ API compatible changes) ### ⚠ `hugr-core` breaking changes ```text --- failure enum_variant_missing: pub enum variant removed or renamed --- Description: A publicly-visible enum has at least one variant that 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/v0.43.0/src/lints/enum_variant_missing.ron Failed in: variant PackageEncodingError::ExtensionVersion, previously in file /tmp/.tmp8eoQo1/hugr-core/src/envelope/package_json.rs:89 --- failure function_parameter_count_changed: pub fn parameter count changed --- Description: A publicly-visible function now takes a different number of parameters. ref: https://doc.rust-lang.org/cargo/reference/semver.html#fn-change-arity impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.43.0/src/lints/function_parameter_count_changed.ron Failed in: hugr_core::import::import_package now takes 3 parameters instead of 2, in /tmp/.tmpBTXSed/hugr/hugr-core/src/import.rs:187 --- failure struct_missing: pub struct removed or renamed --- Description: A publicly-visible struct cannot be imported by its prior path. A `pub use` may have been removed, or the struct itself 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/v0.43.0/src/lints/struct_missing.ron Failed in: struct hugr_core::extension::prelude::PRELUDE_REGISTRY, previously in file /tmp/.tmp8eoQo1/hugr-core/src/extension/prelude.rs:43 struct hugr_core::extension::PRELUDE_REGISTRY, previously in file /tmp/.tmp8eoQo1/hugr-core/src/extension/prelude.rs:43 struct hugr_core::std_extensions::logic::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/logic.rs:134 struct hugr_core::extension::prelude::PRELUDE, previously in file /tmp/.tmp8eoQo1/hugr-core/src/extension/prelude.rs:43 struct hugr_core::extension::PRELUDE, previously in file /tmp/.tmp8eoQo1/hugr-core/src/extension/prelude.rs:43 struct hugr_core::std_extensions::ptr::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/ptr.rs:112 struct hugr_core::std_extensions::arithmetic::int_types::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/arithmetic/int_types.rs:209 struct hugr_core::std_extensions::arithmetic::conversions::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/arithmetic/conversions.rs:174 struct hugr_core::std_extensions::collections::array::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/collections/array.rs:93 struct hugr_core::std_extensions::arithmetic::int_types::INT_TYPES, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/arithmetic/int_types.rs:49 struct hugr_core::std_extensions::arithmetic::float_types::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/arithmetic/float_types.rs:104 struct hugr_core::std_extensions::collections::static_array::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/collections/static_array.rs:142 struct hugr_core::std_extensions::collections::list::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/collections/list.rs:289 struct hugr_core::std_extensions::STD_REG, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions.rs:35 struct hugr_core::std_extensions::collections::value_array::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/collections/value_array.rs:99 struct hugr_core::std_extensions::collections::borrow_array::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/collections/borrow_array.rs:290 struct hugr_core::std_extensions::arithmetic::float_ops::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/arithmetic/float_ops.rs:115 struct hugr_core::std_extensions::arithmetic::int_ops::EXTENSION, previously in file /tmp/.tmp8eoQo1/hugr-core/src/std_extensions/arithmetic/int_ops.rs:254 ``` ### ⚠ `hugr-passes` breaking changes ```text --- failure enum_missing: pub enum removed or renamed --- Description: A publicly-visible enum cannot be imported by its prior path. A `pub use` may have been removed, or the enum itself 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/v0.43.0/src/lints/enum_missing.ron Failed in: enum hugr_passes::non_local::NonLocalEdgesError, previously in file /tmp/.tmp8eoQo1/hugr-passes/src/non_local.rs:57 ``` <details><summary>Changelog</summary> ## `hugr-model` <blockquote> ## [0.23.0](hugr-model-v0.22.4...hugr-model-v0.23.0) - 2025-09-30 ### Bug Fixes - [**breaking**] Appease `cargo-audit` by replacing unmaintained dependencies ([#2572](#2572)) ### New Features - Documentation and error hints ([#2523](#2523)) </blockquote> ## `hugr-core` <blockquote> ## [0.23.0](hugr-core-v0.22.4...hugr-core-v0.23.0) - 2025-09-30 ### Bug Fixes - [**breaking**] Appease `cargo-audit` by replacing unmaintained dependencies ([#2572](#2572)) - *(core)* check extension versions on model import ([#2580](#2580)) - [**breaking**] test extension version compatibility on ModelWithExts ([#2587](#2587)) - *(core)* check used extension versions against resolved extensions ([#2588](#2588)) - [**breaking**] model import loads Package extensions ([#2590](#2590)) ### Miscellaneous Tasks - [**breaking**] Cleanup deprecated definitions ([#2594](#2594)) ### New Features - add trait+funcs for linking Hugrs explicitly by Node ([#2521](#2521)) - Documentation and error hints ([#2523](#2523)) - Allow creating DFG builders from existing hugrs ([#2562](#2562)) - add_input/output for arbitrary DFGBuilders ([#2564](#2564)) - [**breaking**] Return error instead of panicking in DFGWrapper::add_{in,out}put ([#2571](#2571)) - *(core)* inner acccesors for WithGenerator error ([#2583](#2583)) - Normalize CFGs ([#2591](#2591)) ### Refactor - [**breaking**] Replace lazy_static with std::sync::LazyLock ([#2567](#2567)) </blockquote> ## `hugr-llvm` <blockquote> ## [0.23.0](hugr-llvm-v0.22.4...hugr-llvm-v0.23.0) - 2025-09-30 ### Miscellaneous Tasks - [**breaking**] Cleanup deprecated definitions ([#2594](#2594)) ### Refactor - [**breaking**] Replace lazy_static with std::sync::LazyLock ([#2567](#2567)) ### Testing - Add framework for LLVM execution tests involving panics ([#2568](#2568)) </blockquote> ## `hugr-passes` <blockquote> ## [0.23.0](hugr-passes-v0.22.4...hugr-passes-v0.23.0) - 2025-09-30 ### Bug Fixes - DeadCodeElim keeps consumers of linear outputs ([#2560](#2560)) - [**breaking**] Appease `cargo-audit` by replacing unmaintained dependencies ([#2572](#2572)) ### Miscellaneous Tasks - [**breaking**] Cleanup deprecated definitions ([#2594](#2594)) ### New Features - [**breaking**] DeadCodeElimPass reports error on non-existent entry_points ([#2566](#2566)) - Normalize CFGs ([#2591](#2591)) ### Refactor - [**breaking**] Replace lazy_static with std::sync::LazyLock ([#2567](#2567)) </blockquote> ## `hugr-persistent` <blockquote> ## [0.3.0](hugr-persistent-v0.2.3...hugr-persistent-v0.3.0) - 2025-09-30 ### Miscellaneous Tasks - [**breaking**] Cleanup deprecated definitions ([#2594](#2594)) ### Refactor - [**breaking**] Replace lazy_static with std::sync::LazyLock ([#2567](#2567)) </blockquote> ## `hugr` <blockquote> ## [0.23.0](hugr-v0.22.4...hugr-v0.23.0) - 2025-09-30 ### Bug Fixes - DeadCodeElim keeps consumers of linear outputs ([#2560](#2560)) - [**breaking**] Appease `cargo-audit` by replacing unmaintained dependencies ([#2572](#2572)) - *(core)* check extension versions on model import ([#2580](#2580)) - [**breaking**] test extension version compatibility on ModelWithExts ([#2587](#2587)) - *(core)* check used extension versions against resolved extensions ([#2588](#2588)) - [**breaking**] model import loads Package extensions ([#2590](#2590)) ### Miscellaneous Tasks - [**breaking**] Cleanup deprecated definitions ([#2594](#2594)) ### New Features - [**breaking**] DeadCodeElimPass reports error on non-existent entry_points ([#2566](#2566)) - add trait+funcs for linking Hugrs explicitly by Node ([#2521](#2521)) - Documentation and error hints ([#2523](#2523)) - Allow creating DFG builders from existing hugrs ([#2562](#2562)) - add_input/output for arbitrary DFGBuilders ([#2564](#2564)) - [**breaking**] Return error instead of panicking in DFGWrapper::add_{in,out}put ([#2571](#2571)) - *(core)* inner acccesors for WithGenerator error ([#2583](#2583)) - Normalize CFGs ([#2591](#2591)) ### Refactor - [**breaking**] Replace lazy_static with std::sync::LazyLock ([#2567](#2567)) </blockquote> ## `hugr-cli` <blockquote> ## [0.22.3](hugr-cli-v0.22.2...hugr-cli-v0.22.3) - 2025-09-11 ### New Features - *(hugr-cli)* CliError::validate helper ([#2507](#2507)) </blockquote> </details> --- This PR was generated with [release-plz](https://github.com/release-plz/release-plz/).

DeadCodeElim requires consumers of linear outputs of required nodes

9970f0f

acl-cqc marked this pull request as ready for review September 17, 2025 12:15

acl-cqc requested a review from a team as a code owner September 17, 2025 12:15

acl-cqc requested a review from doug-q September 17, 2025 12:15

acl-cqc mentioned this pull request Sep 17, 2025

DCE leaves Hugr in an invalid state #2557

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add PR link...is that good?

f17942c

acl-cqc changed the title ~~fix: DeadCodeElim requires consumers of linear outputs of required nodes~~ fix: DeadCodeElim keep consumers of linear outputs Sep 17, 2025

acl-cqc changed the title ~~fix: DeadCodeElim keep consumers of linear outputs~~ fix: DeadCodeElim keeps consumers of linear outputs Sep 17, 2025

Extend test to demonstrate we do not preserve consumers of copyable v…

e7f6a3e

…alues

aborgna-q approved these changes Sep 17, 2025

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acl-cqc added 3 commits September 17, 2025 20:35

Rewrite using signature of node n

625fb59

Assert entrypoints are present, fix composable::test_then

e5e8f4c

Skip missing entrypoints (Revert "Assert entrypoints are present, fix…

a30f022

… composable::test_then") This reverts commit 1458537bf197cd9248dc28c48b98ce1f36bcfe10. Skip missing entrypoints

acl-cqc added this pull request to the merge queue Sep 18, 2025

Merged via the queue into main with commit de16553 Sep 18, 2025
26 checks passed

acl-cqc deleted the acl/dce_linear branch September 18, 2025 12:11

hugrbot mentioned this pull request Sep 18, 2025

chore: release #2554

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aborgna-q mentioned this pull request Sep 18, 2025

test: Optimize and validate guppy hugr examples CQCL/tket2#1116

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acl-cqc mentioned this pull request Sep 18, 2025

feat!: DeadCodeElimPass reports error on non-existent entry_points #2566

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hugrbot mentioned this pull request Oct 1, 2025

chore: release #2605

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fix: DeadCodeElim keeps consumers of linear outputs #2560

fix: DeadCodeElim keeps consumers of linear outputs #2560

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acl-cqc commented Sep 17, 2025 •

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		for (tgt_n, tgt_port) in h.all_linked_inputs(n) {
		if h.signature(tgt_n)

fix: DeadCodeElim keeps consumers of linear outputs #2560

fix: DeadCodeElim keeps consumers of linear outputs #2560

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