util: amortise symbol_table_baset::next_unused_suffix#9083
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Pull request overview
This PR improves the performance of auto-generated symbol-name allocation by amortising symbol_table_baset::next_unused_suffix(prefix) using a per-prefix “next search-start” hint cache, avoiding repeated linear scans from 0.
Changes:
- Add a per-prefix suffix hint cache to
symbol_table_baset::next_unused_suffix(prefix)to amortise repeated allocations under the same prefix. - Remove
symbol_table_buildert’s now-redundantnext_unused_suffixoverride and reset the inherited cache onclear(). - Update namespace documentation and add a unit test covering the relaxed (non-minimal) suffix semantics, including behavior after erase.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| unit/util/symbol_table.cpp | Adds unit tests for increasing/unique suffix allocation under the new hint-cache semantics. |
| src/util/symbol_table.h | Ensures symbol_tablet::clear() also resets the inherited suffix hint cache. |
| src/util/symbol_table_builder.h | Removes duplicate per-prefix cache logic and relies on symbol_table_baset’s implementation. |
| src/util/symbol_table_base.h | Introduces the per-prefix suffix hint cache and updates next_unused_suffix(prefix) implementation + documentation. |
| src/util/namespace.h | Updates smallest_unused_suffix documentation to describe the now-stateful, non-minimal behavior. |
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## develop #9083 +/- ##
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Coverage 80.68% 80.69%
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Files 1714 1714
Lines 189593 189645 +52
Branches 73 73
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+ Hits 152979 153037 +58
+ Misses 36614 36608 -6 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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next_unused_suffix(prefix) restarted its linear scan from 0 on every call, so allocating N names that share a prefix (as the object factory does) costs O(N^2). Add a per-prefix "next search-start" hint to the base so repeated allocation under the same prefix is amortised O(1). The hint is looked up with try_emplace so the common cache-hit path does not construct/copy the prefix key. The returned suffix is now unused but no longer necessarily the smallest; no caller relies on minimality. This generalises a hint cache that symbol_table_buildert already maintained with the same relaxed semantics, so its now-redundant override (and duplicate cache) is removed; the builder resets the inherited cache on clear(), as does symbol_tablet. namespacet::smallest_unused_suffix's docstring is updated to describe the relaxed, now-stateful contract. It no longer over-claims a global cross-table guarantee: with multiple tables the result is the maximum of each table's per-table value, which is unused in every table only when the tables allocate suffixes monotonically from 0 (as auto-generated symbols do); the single-table common case yields a globally unused suffix. A thread-safety note is added to the base cache. Unit tests cover the new semantics: repeated allocation returns distinct increasing suffixes; uniqueness still holds after erase + re-allocation; clear() resets the hint so allocation restarts at 0; and the same holds through a symbol_table_buildert wrapper, exercising the inherited (no longer overridden) implementation and the builder's cache reset. Co-authored-by: Kiro <kiro-agent@users.noreply.github.com>
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next_unused_suffix(prefix) restarted its linear scan from 0 on every call, so allocating N names that share a prefix (as the object factory does) costs O(N^2). Add a per-prefix "next search-start" hint to the base so repeated allocation under the same prefix is amortised O(1).
The returned suffix is now unused but no longer necessarily the smallest; no caller relies on minimality. This generalises a hint cache that symbol_table_buildert already maintained with the same relaxed semantics, so its now-redundant override (and duplicate cache) is removed; the builder resets the inherited cache on clear(), as does symbol_tablet. namespacet::smallest_unused_suffix's docstring is updated to describe the relaxed, now-stateful contract, and a thread-safety note is added to the base cache.
Add a unit test covering the new semantics: repeated allocation returns distinct increasing suffixes, and uniqueness still holds after erase + re-allocation under the same prefix.