BE-221: HashQL: Implement DBE (Dead Block Elimination)

[indietyp]

🌟 What is the purpose of this PR?

This PR adds a Dead Block Elimination (DBE) pass to the MIR compiler that physically removes unreachable basic blocks from the control-flow graph and compacts the remaining blocks to eliminate gaps in the ID space. This complements the existing CfgSimplify pass which marks unreachable blocks with TerminatorKind::Unreachable but doesn't remove them.

🔍 What does this change?

• Adds a new DeadBlockElimination pass that removes unreachable blocks and compacts the block ID space
• Integrates DBE into the CfgSimplify pass to run after simplifications are applied
• Adds utility methods to IdVec: swap_remove, swap, and truncate to support block compaction
• Adds comprehensive tests for the DBE pass covering various scenarios
• Updates existing test snapshots to reflect the new behavior

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 test suite for the DBE pass covering various scenarios:
  • All blocks reachable
  • Single unreachable block at the end
  • Unreachable block in the middle requiring ID remapping
  • Multiple consecutive unreachable blocks
  • Scattered unreachable blocks requiring complex remapping
  • Switch target remapping
  • Block parameters preservation
  • Unreachable chains of blocks

[indietyp]

• BE-223: HashQL: Fix SSA repair to handle existing block parameters #8136
• BE-221: HashQL: Implement DBE (Dead Block Elimination) #8135 👈 (View in Graphite)
• BE-222: HashQL: Remove span from type environment #8134
• BE-201: HashQL: Implement CFG simplification pass #8133
• BE-220: HashQL: Refactor constant representation with specialized Int type for constant evaluation #8122
• BE-214: HashQL: Implement SSA repair pass for MIR #8093
• BE-218: HashQL: Implement MIR test builder #8092
• BE-217: HashQL: Add PlaceContext for tracking read/write semantics in MIR #8088
• BE-216: HashQL: Implement MIR transform infrastructure #8087
• BE-215: HashQL: Implement dominance frontier and iterated frontier algorithms #8082
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codecov]

Codecov Report

❌ Patch coverage is 98.91697% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.80%. Comparing base (dffec8d) to head (1b3b01b).

Files with missing lines	Patch %	Lines
...bs/@local/hashql/mir/src/pass/transform/dbe/mod.rs	95.23%	3 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                   @@
##           graphite-base/8135    #8135      +/-   ##
======================================================
+ Coverage               57.66%   57.80%   +0.14%     
======================================================
  Files                    1164     1166       +2     
  Lines                  108845   109121     +276     
  Branches                 4956     4963       +7     
======================================================
+ Hits                    62767    63081     +314     
+ Misses                  45346    45306      -40     
- Partials                  732      734       +2     

Flag	Coverage Δ
rust.hashql-compiletest	49.36% <ø> (ø)
rust.hashql-core	82.46% <ø> (ø)
rust.hashql-mir	83.59% <98.91%> (+1.74%)	⬆️
rust.hashql-syntax-jexpr	94.00% <ø> (ø)

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

Your organization requires reapproval when changes are made, so Graphite has dismissed approvals. See the output of git range-diff at https://github.com/hashintel/hash/actions/runs/19819864150

[graphite-app]

Merge activity

• Dec 1, 10:44 AM UTC: Graphite rebased this pull request, because this pull request is set to merge when ready.

[github-actions]

Benchmark results

@rust/hash-graph-benches – Integrations

policy_resolution_large

Function	Value	Mean	Flame graphs
resolve_policies_for_actor	user: empty, selectivity: high, policies: 2002	$$29.0 \mathrm{ms} \pm 133 \mathrm{μs}\left({\color{gray}1.23 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: low, policies: 1	$$3.33 \mathrm{ms} \pm 16.4 \mathrm{μs}\left({\color{gray}2.41 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: medium, policies: 1001	$$13.6 \mathrm{ms} \pm 79.1 \mathrm{μs}\left({\color{red}6.52 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: high, policies: 3314	$$44.2 \mathrm{ms} \pm 301 \mathrm{μs}\left({\color{gray}0.607 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: low, policies: 1	$$14.7 \mathrm{ms} \pm 87.0 \mathrm{μs}\left({\color{gray}2.79 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: medium, policies: 1526	$$25.0 \mathrm{ms} \pm 144 \mathrm{μs}\left({\color{gray}-0.210 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: high, policies: 2078	$$26.9 \mathrm{ms} \pm 112 \mathrm{μs}\left({\color{lightgreen}-39.686 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: low, policies: 1	$$5.16 \mathrm{ms} \pm 31.8 \mathrm{μs}\left({\color{lightgreen}-52.465 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: medium, policies: 1033	$$17.3 \mathrm{ms} \pm 98.6 \mathrm{μs}\left({\color{lightgreen}-46.390 \mathrm{\%}}\right) $$	Flame Graph

policy_resolution_medium

Function	Value	Mean	Flame graphs
resolve_policies_for_actor	user: empty, selectivity: high, policies: 102	$$3.79 \mathrm{ms} \pm 18.4 \mathrm{μs}\left({\color{gray}1.73 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: low, policies: 1	$$2.88 \mathrm{ms} \pm 14.0 \mathrm{μs}\left({\color{gray}-0.944 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: medium, policies: 51	$$3.29 \mathrm{ms} \pm 15.0 \mathrm{μs}\left({\color{gray}-1.107 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: high, policies: 269	$$5.24 \mathrm{ms} \pm 22.9 \mathrm{μs}\left({\color{gray}-1.049 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: low, policies: 1	$$3.50 \mathrm{ms} \pm 14.9 \mathrm{μs}\left({\color{gray}0.994 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: medium, policies: 107	$$4.05 \mathrm{ms} \pm 19.5 \mathrm{μs}\left({\color{gray}-0.531 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: high, policies: 133	$$4.46 \mathrm{ms} \pm 20.6 \mathrm{μs}\left({\color{red}5.22 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: low, policies: 1	$$3.39 \mathrm{ms} \pm 15.8 \mathrm{μs}\left({\color{gray}0.156 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: medium, policies: 63	$$3.95 \mathrm{ms} \pm 21.6 \mathrm{μs}\left({\color{gray}-1.947 \mathrm{\%}}\right) $$	Flame Graph

policy_resolution_none

Function	Value	Mean	Flame graphs
resolve_policies_for_actor	user: empty, selectivity: high, policies: 2	$$2.55 \mathrm{ms} \pm 13.9 \mathrm{μs}\left({\color{gray}4.16 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: low, policies: 1	$$2.53 \mathrm{ms} \pm 12.9 \mathrm{μs}\left({\color{gray}4.98 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: medium, policies: 1	$$2.59 \mathrm{ms} \pm 11.4 \mathrm{μs}\left({\color{gray}3.77 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: high, policies: 8	$$2.78 \mathrm{ms} \pm 15.8 \mathrm{μs}\left({\color{gray}3.44 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: low, policies: 1	$$2.68 \mathrm{ms} \pm 17.1 \mathrm{μs}\left({\color{gray}4.62 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: medium, policies: 3	$$2.87 \mathrm{ms} \pm 16.0 \mathrm{μs}\left({\color{gray}3.04 \mathrm{\%}}\right) $$	Flame Graph

policy_resolution_small

Function	Value	Mean	Flame graphs
resolve_policies_for_actor	user: empty, selectivity: high, policies: 52	$$2.99 \mathrm{ms} \pm 15.4 \mathrm{μs}\left({\color{red}6.42 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: low, policies: 1	$$2.60 \mathrm{ms} \pm 11.3 \mathrm{μs}\left({\color{gray}3.81 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: empty, selectivity: medium, policies: 25	$$2.83 \mathrm{ms} \pm 13.5 \mathrm{μs}\left({\color{red}8.27 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: high, policies: 94	$$3.27 \mathrm{ms} \pm 12.9 \mathrm{μs}\left({\color{gray}2.45 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: low, policies: 1	$$2.86 \mathrm{ms} \pm 17.9 \mathrm{μs}\left({\color{red}5.18 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: seeded, selectivity: medium, policies: 26	$$3.06 \mathrm{ms} \pm 11.2 \mathrm{μs}\left({\color{gray}4.56 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: high, policies: 66	$$3.29 \mathrm{ms} \pm 16.1 \mathrm{μs}\left({\color{red}7.92 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: low, policies: 1	$$2.85 \mathrm{ms} \pm 12.0 \mathrm{μs}\left({\color{red}5.97 \mathrm{\%}}\right) $$	Flame Graph
resolve_policies_for_actor	user: system, selectivity: medium, policies: 29	$$3.12 \mathrm{ms} \pm 15.7 \mathrm{μs}\left({\color{red}5.47 \mathrm{\%}}\right) $$	Flame Graph

read_scaling_complete

Function	Value	Mean	Flame graphs
entity_by_id;one_depth	1 entities	$$40.4 \mathrm{ms} \pm 162 \mathrm{μs}\left({\color{gray}3.59 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;one_depth	10 entities	$$87.7 \mathrm{ms} \pm 470 \mathrm{μs}\left({\color{red}46.9 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;one_depth	25 entities	$$44.3 \mathrm{ms} \pm 194 \mathrm{μs}\left({\color{gray}0.144 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;one_depth	5 entities	$$46.9 \mathrm{ms} \pm 244 \mathrm{μs}\left({\color{gray}0.359 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;one_depth	50 entities	$$55.9 \mathrm{ms} \pm 318 \mathrm{μs}\left({\color{gray}-4.755 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;two_depth	1 entities	$$41.1 \mathrm{ms} \pm 165 \mathrm{μs}\left({\color{gray}-1.450 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;two_depth	10 entities	$$500 \mathrm{ms} \pm 835 \mathrm{μs}\left({\color{red}133 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;two_depth	25 entities	$$102 \mathrm{ms} \pm 520 \mathrm{μs}\left({\color{gray}1.64 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;two_depth	5 entities	$$86.5 \mathrm{ms} \pm 362 \mathrm{μs}\left({\color{gray}1.69 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;two_depth	50 entities	$$295 \mathrm{ms} \pm 831 \mathrm{μs}\left({\color{gray}-0.589 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;zero_depth	1 entities	$$15.0 \mathrm{ms} \pm 86.1 \mathrm{μs}\left({\color{gray}-0.263 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;zero_depth	10 entities	$$15.1 \mathrm{ms} \pm 65.1 \mathrm{μs}\left({\color{gray}-1.161 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;zero_depth	25 entities	$$15.5 \mathrm{ms} \pm 87.2 \mathrm{μs}\left({\color{gray}0.305 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;zero_depth	5 entities	$$15.1 \mathrm{ms} \pm 81.5 \mathrm{μs}\left({\color{gray}-0.733 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id;zero_depth	50 entities	$$18.7 \mathrm{ms} \pm 89.6 \mathrm{μs}\left({\color{gray}0.758 \mathrm{\%}}\right) $$	Flame Graph

read_scaling_linkless

Function	Value	Mean	Flame graphs
entity_by_id	1 entities	$$15.4 \mathrm{ms} \pm 80.2 \mathrm{μs}\left({\color{gray}2.68 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	10 entities	$$15.0 \mathrm{ms} \pm 62.3 \mathrm{μs}\left({\color{gray}-0.372 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	100 entities	$$15.2 \mathrm{ms} \pm 80.2 \mathrm{μs}\left({\color{gray}0.686 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	1000 entities	$$15.8 \mathrm{ms} \pm 76.5 \mathrm{μs}\left({\color{gray}0.113 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	10000 entities	$$22.6 \mathrm{ms} \pm 162 \mathrm{μs}\left({\color{gray}-1.460 \mathrm{\%}}\right) $$	Flame Graph

representative_read_entity

Function	Value	Mean	Flame graphs
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/block/v/1	$$30.8 \mathrm{ms} \pm 288 \mathrm{μs}\left({\color{gray}1.54 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/book/v/1	$$30.4 \mathrm{ms} \pm 348 \mathrm{μs}\left({\color{gray}0.774 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/building/v/1	$$30.6 \mathrm{ms} \pm 307 \mathrm{μs}\left({\color{lightgreen}-5.110 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/organization/v/1	$$30.9 \mathrm{ms} \pm 294 \mathrm{μs}\left({\color{gray}-3.893 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/page/v/2	$$30.3 \mathrm{ms} \pm 318 \mathrm{μs}\left({\color{gray}-0.062 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/person/v/1	$$29.3 \mathrm{ms} \pm 290 \mathrm{μs}\left({\color{lightgreen}-6.050 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/playlist/v/1	$$30.9 \mathrm{ms} \pm 284 \mathrm{μs}\left({\color{lightgreen}-6.796 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/song/v/1	$$29.8 \mathrm{ms} \pm 318 \mathrm{μs}\left({\color{gray}-1.207 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/uk-address/v/1	$$30.8 \mathrm{ms} \pm 315 \mathrm{μs}\left({\color{gray}-2.226 \mathrm{\%}}\right) $$	Flame Graph

representative_read_entity_type

Function	Value	Mean	Flame graphs
get_entity_type_by_id	Account ID: bf5a9ef5-dc3b-43cf-a291-6210c0321eba	$$9.06 \mathrm{ms} \pm 48.4 \mathrm{μs}\left({\color{gray}0.670 \mathrm{\%}}\right) $$	Flame Graph

representative_read_multiple_entities

Function	Value	Mean	Flame graphs
entity_by_property	traversal_paths=0	0	$$58.0 \mathrm{ms} \pm 422 \mathrm{μs}\left({\color{gray}1.39 \mathrm{\%}}\right) $$
entity_by_property	traversal_paths=255	1,resolve_depths=inherit:1;values:255;properties:255;links:127;link_dests:126;type:true	$$110 \mathrm{ms} \pm 508 \mathrm{μs}\left({\color{gray}0.685 \mathrm{\%}}\right) $$
entity_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:0;properties:0;links:0;link_dests:0;type:false	$$63.4 \mathrm{ms} \pm 321 \mathrm{μs}\left({\color{gray}0.981 \mathrm{\%}}\right) $$
entity_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:0;properties:0;links:1;link_dests:0;type:true	$$71.5 \mathrm{ms} \pm 383 \mathrm{μs}\left({\color{gray}0.021 \mathrm{\%}}\right) $$
entity_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:0;properties:2;links:1;link_dests:0;type:true	$$81.8 \mathrm{ms} \pm 399 \mathrm{μs}\left({\color{gray}0.460 \mathrm{\%}}\right) $$
entity_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:2;properties:2;links:1;link_dests:0;type:true	$$88.4 \mathrm{ms} \pm 410 \mathrm{μs}\left({\color{gray}0.085 \mathrm{\%}}\right) $$
link_by_source_by_property	traversal_paths=0	0	$$52.6 \mathrm{ms} \pm 330 \mathrm{μs}\left({\color{gray}1.59 \mathrm{\%}}\right) $$
link_by_source_by_property	traversal_paths=255	1,resolve_depths=inherit:1;values:255;properties:255;links:127;link_dests:126;type:true	$$81.6 \mathrm{ms} \pm 308 \mathrm{μs}\left({\color{gray}-0.638 \mathrm{\%}}\right) $$
link_by_source_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:0;properties:0;links:0;link_dests:0;type:false	$$59.5 \mathrm{ms} \pm 391 \mathrm{μs}\left({\color{gray}2.49 \mathrm{\%}}\right) $$
link_by_source_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:0;properties:0;links:1;link_dests:0;type:true	$$68.0 \mathrm{ms} \pm 367 \mathrm{μs}\left({\color{gray}1.58 \mathrm{\%}}\right) $$
link_by_source_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:0;properties:2;links:1;link_dests:0;type:true	$$70.5 \mathrm{ms} \pm 370 \mathrm{μs}\left({\color{gray}1.73 \mathrm{\%}}\right) $$
link_by_source_by_property	traversal_paths=2	1,resolve_depths=inherit:0;values:2;properties:2;links:1;link_dests:0;type:true	$$70.1 \mathrm{ms} \pm 297 \mathrm{μs}\left({\color{gray}0.793 \mathrm{\%}}\right) $$

scenarios

Function	Value	Mean	Flame graphs
full_test	query-limited	$$145 \mathrm{ms} \pm 557 \mathrm{μs}\left({\color{gray}1.39 \mathrm{\%}}\right) $$	Flame Graph
full_test	query-unlimited	$$141 \mathrm{ms} \pm 580 \mathrm{μs}\left({\color{gray}-0.996 \mathrm{\%}}\right) $$	Flame Graph
linked_queries	query-limited	$$42.6 \mathrm{ms} \pm 227 \mathrm{μs}\left({\color{lightgreen}-59.083 \mathrm{\%}}\right) $$	Flame Graph
linked_queries	query-unlimited	$$572 \mathrm{ms} \pm 1.24 \mathrm{ms}\left({\color{gray}-0.304 \mathrm{\%}}\right) $$	Flame Graph