Fix poor performance of sameSource predicate #907
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Pull Request Overview
This PR addresses performance issues in the sameSource predicate by preventing premature inlining and constraining its bindings.
- Switches from
inlinetoinline_lateto avoid heavy common-subexpression expansion - Adds a
bindingset[a, b]directive to limit predicate instantiations
Comments suppressed due to low confidence (1)
cpp/common/src/codingstandards/cpp/rules/iofstreammissingpositioning/IOFstreamMissingPositioning.qll:54
- [nitpick] Consider adding a comment above this pragma to explain that
inline_lateis used to prevent early inlining and avoid expensive common-subexpression optimizations that degrade performance.
pragma[inline_late]
...on/src/codingstandards/cpp/rules/iofstreammissingpositioning/IOFstreamMissingPositioning.qll
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/test-performance |
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🏁 Beep Boop! Performance testing for this PR has been initiated. Please check back later for results. Note that the query package generation step must complete before testing will start so it might be a minute. |
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🏁 Beep Boop! Performance testing complete! See below for performance of the last 3 runs vs your PR. Times are based on predicate performance. You can find full graphs and stats in the PR that was created for this test in the release engineering repo. 🏁 Below are the slowest predicates for the last 2 releases vs this PR. |
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Performance results appear reasonable to me. |
lcartey
approved these changes
Jun 6, 2025
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Thank you @smowton ! 🎉 🎉 🎉 |
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Description
User at github/codeql#19633 observed that
sameSourcecould be a potentially-large cost in running thecodeql/[email protected]suite.I noticed that while the inline pragma made clear that the intent was never to materialise
sameSourcein its entirety but rather only to identify if two file-accesses referred to the same source once the two candidates had been otherwise constrained, in practice a common-subexpression pass was lifting the general square of all possibly-aliasing file accesses into a#sharedpredicate.Switching to
inline_lateinstead defeats this potential misoptimisation, and at least for the linked discussion makes the suite once again run on a practical timescale.Change request type
.ql,.qll,.qlsor unit tests)Rules with added or modified queries
FIO39-CFIO50-CPPA27-0-3RULE-30-0-2Release change checklist
A change note (development_handbook.md#change-notes) is required for any pull request which modifies:
If you are only adding new rule queries, a change note is not required.
Author: Is a change note required?
🚨🚨🚨
Reviewer: Confirm that format of shared queries (not the .qll file, the
.ql file that imports it) is valid by running them within VS Code.
Reviewer: Confirm that either a change note is not required or the change note is required and has been added.
Query development review checklist
For PRs that add new queries or modify existing queries, the following checklist should be completed by both the author and reviewer:
Author
As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.
Reviewer
As a rule of thumb, predicates specific to the query should take no more than 1 minute, and for simple queries be under 10 seconds. If this is not the case, this should be highlighted and agreed in the code review process.