perf: move BasicBlock type check from __iter__ to insertion methods#198
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MatthieuDartiailh merged 4 commits intoMay 12, 2026
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The isinstance check on every yielded item in BasicBlock.__iter__ was purely defensive — it detected invalid types that had already entered the list. Moving it to append/extend/insert/__setitem__ catches invalid types at the point of insertion instead, eliminating the check from the hot iteration path entirely. The structural checks (jump must be last, jump/TryBegin target must be a BasicBlock) remain in __iter__ as they depend on the full block context and cannot be verified at insertion time. Profiling data | Hotspot | Before | After | |---|---|---| | `BasicBlock.__iter__` own | 4.91% | 2.82% | | `ControlFlowGraph.from_bytecode` own | 4.61% | 4.04% | Throughput (Bytecode.from_code().to_code() on dis module's code object, 1 second timed window, 5 runs): | | r/s range | |---|---| | Before | 133–144 | | After | 142–144 |
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #198 +/- ##
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+ Coverage 95.19% 95.24% +0.05%
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Files 7 7
Lines 2061 2083 +22
Branches 446 449 +3
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+ Hits 1962 1984 +22
Misses 55 55
Partials 44 44 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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MatthieuDartiailh
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I would like to see an extra test but otherwise LGTM
MatthieuDartiailh
previously approved these changes
May 11, 2026
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Actually looking at codecov report you are missing test cases for valid setitem (index and slice). |
MatthieuDartiailh
approved these changes
May 12, 2026
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The isinstance check on every yielded item in BasicBlock.iter was purely defensive — it detected invalid types that had already entered the list. Moving it to append/extend/insert/setitem catches invalid types at the point of insertion instead, eliminating the check from the hot iteration path entirely.
The structural checks (jump must be last, jump/TryBegin target must be a BasicBlock) remain in iter as they depend on the full block context and cannot be verified at insertion time.
Profiling data
BasicBlock.__iter__ownControlFlowGraph.from_bytecodeownThroughput (Bytecode.from_code().to_code() on dis module's code object, 1 second timed window, 5 runs):