Skip rename_symbolt::rename when maps are empty#8974
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Pull request overview
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Avoids an unnecessary full expression-tree traversal in rename_symbolt::rename(exprt&) when there are no renaming rules, improving library-link-time performance in no-op cases.
Changes:
- Add an early return in
rename_symbolt::rename(exprt&)when bothexpr_mapandtype_mapare empty.
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## develop #8974 +/- ##
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Coverage 80.68% 80.68%
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Files 1713 1714 +1
Lines 189462 189479 +17
Branches 73 73
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+ Hits 152860 152890 +30
+ Misses 36602 36589 -13 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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rename_symbolt::rename(exprt) creates a depth_iterator and walks the entire expression tree even when both expr_map and type_map are empty. This happens during library linking when no symbols need renaming. Add an early return to avoid the wasted traversal, mirroring the existing short-circuits in have_to_rename(). Factor the repeated `expr_map.empty() && type_map.empty()` check (now in rename(exprt&) and both have_to_rename overloads) into a public rename_symbolt::empty() helper, so the predicate has a single definition and a future third map cannot be missed. Add a unit test (unit/util/rename_symbol.cpp; there were none for rename_symbolt) pinning the documented contract: empty maps leave the expression unchanged and return true, while a populated map renames the matching symbol and returns false. Performance: the change removes a full expression-tree traversal on every empty-map rename call. Measured with goto-cc/cbmc built with and without the early return (in-source -O2, medians): - goto-cc linking a large object (8000 functions, ~8 MB goto binary) with empty rename maps: 1.97s -> 1.94s (~ -1.6%) -- the library-linking scenario this targets; - goto-cc compile+link and cbmc --program-only of CSmith programs: within measurement noise (<= 1%, both signs), i.e. no regression on workloads that do not stress empty-map renaming. Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
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rename_symbolt::rename(exprt) creates a depth_iterator and walks the entire expression tree even when both expr_map and type_map are empty. This happens during library linking when no symbols need renaming. Add an early return to avoid the wasted traversal.