CPP: Disable dynamic reordering for AliasedSSA::isCoveredOffset - #22480
Merged
Conversation
Contributor
There was a problem hiding this comment.
Copilot review overview
🟢 Approval recommended
The targeted pragma correctly implements the documented performance workaround without affecting default evaluation behavior.
Review tier: Balanced
Findings: None
What changed in this PR
Disables dynamic join ordering for AliasedSSA::isCoveredOffset to prevent severe Wireshark evaluation regressions.
Changes:
- Adds the
no_dynamic_join_orderpragma to the affected predicate.
| File | Description |
|---|---|
cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll |
Opts isCoveredOffset out of dynamic join ordering. |
💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
We are working on a new dynamic join orderer for CodeQL that join orders predicates at evaluation-time using run-time cardinality information instead of relying on a statically chosen join order decided at compilation-time. At the moment the
AliasedSSA::isCoveredOffsetpredicate is join ordered badly by the dynamic join orderer, leading to a catastrophic join regression forwireshark. This PR disables dynamic join ordering for this particular predicate, while we work on improving the dynamic join orderer.Dynamic join ordering is still disabled by default during compilation and evaluation and the
no_dynamic_join_orderpragma has no effect on compilation when dynamic join ordering is not explicitly enabled during compilation.