[LifetimeSafety] Add loan expiry analysis by usx95 · Pull Request #148712 · llvm/llvm-project

usx95 · 2025-07-14T19:38:39Z

This PR adds the ExpiredLoansAnalysis class to track which loans have expired. The analysis uses a dataflow lattice (ExpiredLattice) to maintain the set of expired loans at each program point.

This is a very light weight dataflow analysis and is expected to reach fixed point in ~2 iterations.
In principle, this does not need a dataflow analysis but is used for convenience in favour of lean code.

usx95 · 2025-07-14T19:38:56Z

[LifetimeSafety] Add loan expiry analysis #148712 : 2 dependent PRs (#148976 , #149731 ) 👈 (View in Graphite)
[LifetimeSafety] Revamp test suite using unittests #149158
[LifetimeSafety] Add per-program-point lattice tracking #149199
main

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

usx95 · 2025-07-18T14:28:33Z

Added unit tests for loan expiry!

ymand · 2025-07-18T18:35:03Z


+// ========================================================================= //
+//                         Expired Loans Analysis
+// ========================================================================= //


nit: add dash.

Can you please add a suggestion? I don't quite get the location where you are referring.

ymand · 2025-07-18T19:58:19Z

+  }
+
+  Lattice transfer(Lattice In, const IssueFact &F) {
+    return Lattice(Factory.remove(In.Expired, F.getLoanID()));


Might be worth explaining why this is necessary. Specifically, now its possible that the loan would appear in In.Expired at all to be worth removing. I assume this arises because of backedges.

Done. There is a subtle false negative due to this as well. Mentioned that.

Xazax-hun

Once the comments are addressed it looks good to me.

jvoung

LG too!

usx95 · 2025-07-23T10:12:55Z

Merge activity

Jul 23, 10:12 AM UTC: A user started a stack merge that includes this pull request via Graphite.
Jul 23, 10:14 AM UTC: @usx95 merged this pull request with Graphite.

This PR adds the `ExpiredLoansAnalysis` class to track which loans have expired. The analysis uses a dataflow lattice (`ExpiredLattice`) to maintain the set of expired loans at each program point. This is a very light weight dataflow analysis and is expected to reach fixed point in ~2 iterations. In principle, this does not need a dataflow analysis but is used for convenience in favour of lean code.

Refactored the lifetime safety analysis to use a generic dataflow framework with a policy-based design. - Introduced a generic `DataflowAnalysis` template class that can be specialized for different analyses - Renamed `LifetimeLattice` to `LoanPropagationLattice` to better reflect its purpose - Created a `LoanPropagationAnalysis` class that inherits from the generic framework - Moved transfer functions from the standalone `Transferer` class into the analysis class - Restructured the code to separate the dataflow engine from the specific analysis logic - Updated debug output and test expectations to use the new class names In order to add more analyses, e.g. [loan expiry](llvm#148712) and origin liveness, the previous implementation would have separate, nearly identical dataflow runners for each analysis. This change creates a single, reusable component, which will make it much simpler to add subsequent analyses without repeating boilerplate code. This is quite close to the existing dataflow framework!

This PR adds the `ExpiredLoansAnalysis` class to track which loans have expired. The analysis uses a dataflow lattice (`ExpiredLattice`) to maintain the set of expired loans at each program point. This is a very light weight dataflow analysis and is expected to reach fixed point in ~2 iterations. In principle, this does not need a dataflow analysis but is used for convenience in favour of lean code.

Refactored the lifetime safety analysis to use a generic dataflow framework with a policy-based design. ### Changes - Introduced a generic `DataflowAnalysis` template class that can be specialized for different analyses - Renamed `LifetimeLattice` to `LoanPropagationLattice` to better reflect its purpose - Created a `LoanPropagationAnalysis` class that inherits from the generic framework - Moved transfer functions from the standalone `Transferer` class into the analysis class - Restructured the code to separate the dataflow engine from the specific analysis logic - Updated debug output and test expectations to use the new class names ### Motivation In order to add more analyses, e.g. [loan expiry](llvm/llvm-project#148712) and origin liveness, the previous implementation would have separate, nearly identical dataflow runners for each analysis. This change creates a single, reusable component, which will make it much simpler to add subsequent analyses without repeating boilerplate code. This is quite close to the existing dataflow framework!

usx95 mentioned this pull request Jul 14, 2025

[LifetimeSafety] Make the dataflow analysis generic #148222

Merged

usx95 changed the title ~~users/usx95/lifetime-safety-add-loan-expiry~~ [LifetimeSafety] Add loan expiry analysis Jul 14, 2025

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 880cf3b to ed73e3b Compare July 14, 2025 19:49

usx95 force-pushed the users/usx95/lifetime-safety-liveness branch from c217d0d to 702d255 Compare July 14, 2025 19:49

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from ed73e3b to a50b00e Compare July 14, 2025 19:52

usx95 force-pushed the users/usx95/lifetime-safety-liveness branch 2 times, most recently from 7e098b0 to 793d58e Compare July 14, 2025 20:02

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from a50b00e to a9f1e8d Compare July 14, 2025 20:03

usx95 added this to Lifetime Safety in Clang Jul 14, 2025

usx95 self-assigned this Jul 14, 2025

usx95 moved this to Todo in Lifetime Safety in Clang Jul 14, 2025

usx95 force-pushed the users/usx95/lifetime-safety-liveness branch from 793d58e to 2bff132 Compare July 15, 2025 09:09

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch 5 times, most recently from 6ce3173 to 9265536 Compare July 15, 2025 10:27

usx95 force-pushed the users/usx95/lifetime-safety-liveness branch from 2253ff0 to c073ef3 Compare July 15, 2025 10:27

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 9265536 to 9da8f3a Compare July 15, 2025 10:47

usx95 force-pushed the users/usx95/lifetime-safety-liveness branch from c073ef3 to 51afc3e Compare July 15, 2025 10:47

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 9da8f3a to 04d6193 Compare July 15, 2025 17:53

usx95 force-pushed the users/usx95/lifetime-safety-liveness branch from 51afc3e to 7b26a72 Compare July 15, 2025 17:53

usx95 mentioned this pull request Jul 15, 2025

[LifetimeSafety] Support bidirectional dataflow analysis #148967

Merged

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 04d6193 to 2073937 Compare July 15, 2025 21:33

usx95 changed the base branch from users/usx95/lifetime-safety-liveness to users/usx95/07-15-add-backward-analysis-capability July 15, 2025 21:35

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch 2 times, most recently from 5f09913 to aca68c2 Compare July 15, 2025 21:54

usx95 force-pushed the users/usx95/07-15-add-backward-analysis-capability branch from b109b6a to 7502ee5 Compare July 15, 2025 21:54

usx95 requested a review from jvoung July 15, 2025 22:03

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 8c5c8f1 to c29040a Compare July 18, 2025 14:27

usx95 requested a review from Xazax-hun July 18, 2025 14:28

This was referenced Jul 18, 2025

[LifetimeSafety] Enhance benchmark script for new sub analyses #149577

Merged

[LifetimeSafety] Implement a basic use-after-free diagnostic #149731

Merged

ymand approved these changes Jul 21, 2025

View reviewed changes

Xazax-hun approved these changes Jul 21, 2025

View reviewed changes

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from c29040a to 6ad27da Compare July 21, 2025 14:48

usx95 force-pushed the users/usx95/07-16-lifetime-safety-add-unit-tests branch from e6fc855 to ad8d8a8 Compare July 21, 2025 22:04

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 6ad27da to 7ec322f Compare July 21, 2025 22:05

Base automatically changed from users/usx95/07-16-lifetime-safety-add-unit-tests to main July 22, 2025 10:32

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 7ec322f to 65f5402 Compare July 22, 2025 10:33

jvoung approved these changes Jul 23, 2025

View reviewed changes

[LifetimeSafety] Add loan expiry analysis

7a78e40

usx95 force-pushed the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch from 65f5402 to 7a78e40 Compare July 23, 2025 09:53

usx95 merged commit ffdada1 into main Jul 23, 2025
7 of 9 checks passed

usx95 deleted the users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry branch July 23, 2025 10:14

github-project-automation Bot moved this from In Progress to Done in Lifetime Safety in Clang Jul 23, 2025

usx95 added the clang:temporal-safety Issue/FR relating to the lifetime analysis in Clang (-Wdangling, -Wreturn-local-addr) label Aug 22, 2025

usx95 mentioned this pull request Sep 4, 2025

[LifetimeSafety] Associate origins to all l-valued expressions #156896

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[LifetimeSafety] Add loan expiry analysis#148712

[LifetimeSafety] Add loan expiry analysis#148712
usx95 merged 1 commit into
mainfrom
users/usx95/07-14-users_usx95_lifetime-safety-add-loan-expiry

usx95 commented Jul 14, 2025 •

edited

Loading

Uh oh!

usx95 commented Jul 14, 2025 •

edited

Loading

Uh oh!

usx95 commented Jul 18, 2025

Uh oh!

Uh oh!

ymand Jul 18, 2025

Uh oh!

usx95 Jul 21, 2025

Uh oh!

ymand Jul 18, 2025

Uh oh!

usx95 Jul 21, 2025

Uh oh!

Xazax-hun left a comment

Uh oh!

jvoung left a comment

Uh oh!

usx95 commented Jul 23, 2025 •

edited

Loading

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

Conversation

usx95 commented Jul 14, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

usx95 commented Jul 14, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

usx95 commented Jul 18, 2025

Uh oh!

Uh oh!

ymand Jul 18, 2025

Choose a reason for hiding this comment

Uh oh!

usx95 Jul 21, 2025

Choose a reason for hiding this comment

Uh oh!

ymand Jul 18, 2025

Choose a reason for hiding this comment

Uh oh!

usx95 Jul 21, 2025

Choose a reason for hiding this comment

Uh oh!

Xazax-hun left a comment

Choose a reason for hiding this comment

Uh oh!

jvoung left a comment

Choose a reason for hiding this comment

Uh oh!

usx95 commented Jul 23, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Merge activity

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

usx95 commented Jul 14, 2025 •

edited

Loading

usx95 commented Jul 14, 2025 •

edited

Loading

usx95 commented Jul 23, 2025 •

edited

Loading