BE-494: HashQL: Loop-breaker selection for recursive inlining by indietyp · Pull Request #8600 · hashintel/hash

indietyp · 2026-03-31T20:23:08Z

🌟 What is the purpose of this PR?

This PR implements a three-color depth-first search algorithm for directed graphs and integrates it with a loop-breaker selection system for the MIR inliner. The three-color DFS enables cycle detection and postorder traversal, while the loop-breaker system allows the inliner to handle mutually recursive functions by strategically selecting which functions to avoid inlining within strongly connected components (SCCs).

🔗 Related links

Related to MIR optimization and inlining strategies for recursive function groups

🔍 What does this change?

Adds a new three-color depth-first search implementation in libs/@local/hashql/core/src/graph/algorithms/color/mod.rs with support for cycle detection and visitor callbacks
Implements a loop-breaker selection algorithm in libs/@local/hashql/mir/src/pass/transform/inline/loop_breaker.rs that uses scoring heuristics to choose which functions in recursive SCCs should not be inlined
Extends the inline pass to process SCCs with loop-breaker awareness, allowing inlining of non-breaker functions while avoiding infinite recursion
Adds comprehensive test coverage for both the three-color DFS algorithm and loop-breaker selection
Updates the call graph analysis to support querying callers of a function
Adds iterator support for SCC members with both immutable and mutable access
Changes unary NOT operator representation from ! to ~ in MIR output formatting
Extends inline configuration with InlineLoopBreakerConfig for tuning breaker selection heuristics

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

does not modify any publishable blocks or libraries, or modifications do not need publishing

📜 Does this require a change to the docs?

The changes in this PR:

are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

do not affect the execution graph

🛡 What tests cover this?

Comprehensive unit tests for three-color DFS including cycle detection, postorder traversal, edge filtering, and state accumulation
Loop-breaker selection tests covering mutual recursion, cost-based selection, multi-cycle SCCs, and ordering verification
Integration tests showing the complete inlining behavior with loop breakers
Existing MIR transformation tests updated to reflect the new unary operator formatting

❓ How to test this?

Run the test suite to verify all three-color DFS and loop-breaker functionality
Test with mutually recursive MIR functions to confirm proper breaker selection and inlining behavior
Verify that the inliner no longer gets stuck in infinite loops when processing recursive function groups

vercel · 2026-03-31T20:23:14Z

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Project	Deployment	Actions	Updated (UTC)
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indietyp · 2026-03-31T20:23:38Z

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codecov · 2026-03-31T20:26:50Z

Codecov Report

❌ Patch coverage is 90.28213% with 62 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.34%. Comparing base (f1bc346) to head (9b23aee).

Files with missing lines	Patch %	Lines
...cal/hashql/core/src/graph/algorithms/tarjan/mod.rs	0.00%	22 Missing ⚠️
...shql/mir/src/pass/transform/inline/loop_breaker.rs	90.00%	9 Missing and 4 partials ⚠️
...ocal/hashql/mir/src/pass/transform/inline/tests.rs	94.62%	9 Missing and 4 partials ⚠️
...ocal/hashql/core/src/graph/algorithms/color/mod.rs	93.24%	5 Missing ⚠️
...al/hashql/core/src/graph/algorithms/color/tests.rs	96.21%	4 Missing and 1 partial ⚠️
...@local/hashql/mir/src/pass/transform/inline/mod.rs	89.65%	1 Missing and 2 partials ⚠️
...local/hashql/mir/src/pass/transform/inline/find.rs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                                     Coverage Diff                                      @@
##           bm/be-482-hashql-remove-logical-not-from-unary-operators    #8600      +/-   ##
============================================================================================
+ Coverage                                                     62.76%   69.34%   +6.57%     
============================================================================================
  Files                                                          1243     1096     -147     
  Lines                                                        133430   110894   -22536     
  Branches                                                       5404     5117     -287     
============================================================================================
- Hits                                                          83753    76895    -6858     
+ Misses                                                        48812    33190   -15622     
+ Partials                                                        865      809      -56

Flag	Coverage Δ
apps.hash-ai-worker-ts	`1.41% <ø> (ø)`
apps.hash-api	`0.00% <ø> (ø)`
local.claude-hooks	`?`
local.harpc-client	`?`
local.hash-backend-utils	`2.81% <ø> (ø)`
local.hash-graph-sdk	`9.63% <ø> (ø)`
local.hash-isomorphic-utils	`0.00% <ø> (ø)`
rust.harpc-wire-protocol	`?`
rust.hash-graph-api	`2.52% <ø> (ø)`
rust.hash-graph-authorization	`?`
rust.hash-graph-postgres-store	`?`
rust.hash-graph-temporal-versioning	`?`
rust.hash-graph-types	`?`
rust.hash-graph-validation	`?`
rust.hashql-ast	`87.23% <ø> (ø)`
rust.hashql-compiletest	`28.26% <ø> (ø)`
rust.hashql-core	`82.25% <85.96%> (+0.03%)`	⬆️
rust.hashql-eval	`79.71% <ø> (ø)`
rust.hashql-hir	`89.06% <ø> (?)`
rust.hashql-mir	`91.68% <92.68%> (+0.01%)`	⬆️
rust.hashql-syntax-jexpr	`94.06% <ø> (ø)`

Flags with carried forward coverage won't be shown. Click here to find out more.

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codspeed-hq · 2026-03-31T20:27:22Z

Merging this PR will not alter performance

✅ 80 untouched benchmarks

_{Comparing bm/be-494-hashql-scc-loop-breaker-inlining (9b23aee) with bm/be-482-hashql-remove-logical-not-from-unary-operators (256f483)¹}

No successful run was found on bm/be-482-hashql-remove-logical-not-from-unary-operators (f1bc346) during the generation of this report, so b55578c was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

vercel · 2026-03-31T20:56:59Z

Deployment failed with the following error:

Invalid request: `attribution.gitUser` should NOT have additional property `isBot`.

cursor · 2026-04-29T15:42:47Z

PR Summary

Medium Risk
Changes MIR inlining behavior for recursive call graphs by introducing loop-breaker selection and new traversal logic; incorrect breaker selection or SCC ordering could cause missed inlining opportunities or regressions in optimization/cycle handling.

Overview
Adds a new graph::algorithms::color module implementing iterative three-color DFS (TriColorDepthFirstSearch + TriColorVisitor) with cycle detection and postorder callbacks, plus unit tests.

Updates Tarjan SCC member storage to support iterating/mutating per-SCC member slices (Members::iter/iter_mut and IntoIterator), and extends CallGraph with callers() to support caller-count queries.

Refactors the MIR inliner to handle recursive SCCs via loop breakers: introduces InlineLoopBreakerConfig and loop_breaker::LoopBreaker to greedily pick breaker functions per SCC (based on cost/directives/caller counts), reorder SCC members for processing, and skip inlining calls to breakers/self-calls in both normal and aggressive filter phases; adds extensive tests and new UI snapshots validating the new behavior.

^{Reviewed by Cursor Bugbot for commit 9b23aee. Bugbot is set up for automated code reviews on this repo. Configure here.}

augmentcode · 2026-04-29T17:38:29Z

🤖 Augment PR Summary

Summary: Adds loop-breaker-aware inlining for mutually recursive HashQL MIR functions, enabling safe inlining within recursive SCCs without infinite expansion.

Changes:

Introduces an iterative three-color DFS utility (with cycle detection and postorder callbacks) in hashql_core::graph::algorithms::color.
Adds loop-breaker selection (loop_breaker.rs) that scores SCC members and greedily picks a feedback-vertex set to break recursion.
Reorders SCC members so non-breakers are processed in postorder of the breaker-removed DAG, followed by breakers, improving within-SCC optimization ordering.
Extends the MIR inliner to inline within SCCs except for self-calls and calls targeting loop breakers.
Enhances call graph analysis with a callers(def) iterator and SCC member iteration helpers.
Updates MIR formatting/tests to render unary NOT as ~ (instead of !) and refreshes snapshots.
Adds substantial unit/integration tests covering breaker selection, multi-breaker SCCs, ordering, and aggressive filter behavior.

Technical Notes: Breaker selection uses repeated cycle checks over the remaining subgraph (filtered via DFS edge ignoring) to ensure the non-breaker remainder is acyclic before allowing within-SCC inlining.

_{🤖 Was this summary useful? React with 👍 or 👎}

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Review completed. 2 suggestions posted.

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cursor

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 4ea12a3. Configure here.}

indietyp added 3 commits March 31, 2026 21:03

feat: loop breaker impl

1254ed6

chore: fix tests

7355d71

chore: tests

87ea02b

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github-actions Bot added area/libs Relates to first-party libraries/crates/packages (area) type/eng > backend Owned by the @backend team area/tests New or updated tests labels Mar 31, 2026

indietyp mentioned this pull request Mar 31, 2026

BE-482: HashQL: Remove logical not from MIR and fix postgres boolean lowering #8595

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fix: aggressive

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fix: clippy

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indietyp force-pushed the bm/be-482-hashql-remove-logical-not-from-unary-operators branch from 51195eb to d6dbdd5 Compare March 31, 2026 20:56

indietyp force-pushed the bm/be-494-hashql-scc-loop-breaker-inlining branch from f66d5ce to b4e6aaf Compare March 31, 2026 20:56

indietyp force-pushed the bm/be-494-hashql-scc-loop-breaker-inlining branch from 933ed9e to 1bebdcc Compare April 29, 2026 15:32

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indietyp force-pushed the bm/be-494-hashql-scc-loop-breaker-inlining branch 2 times, most recently from 1cba715 to 1da0f0a Compare April 29, 2026 15:42

indietyp marked this pull request as ready for review April 29, 2026 15:42

fix: lint

ac42f9a

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indietyp force-pushed the bm/be-482-hashql-remove-logical-not-from-unary-operators branch from 1c91f7b to 84e917d Compare April 29, 2026 15:51

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indietyp force-pushed the bm/be-482-hashql-remove-logical-not-from-unary-operators branch from 84e917d to d7a892b Compare April 30, 2026 08:53

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chore: fix doclinks

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Conversation

indietyp commented Mar 31, 2026

🌟 What is the purpose of this PR?

🔗 Related links

🔍 What does this change?

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

📜 Does this require a change to the docs?

🕸️ Does this require a change to the Turbo Graph?

🛡 What tests cover this?

❓ How to test this?

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Merging this PR will not alter performance

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