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Title: Bytecode parity - CFG reorders and LOAD_FAST_BORROW chain by youknowone · Pull Request #7870 · RustPython/RustPython · GitHub

Open Graph Title: Bytecode parity - CFG reorders and LOAD_FAST_BORROW chain by youknowone · Pull Request #7870 · RustPython/RustPython

X Title: Bytecode parity - CFG reorders and LOAD_FAST_BORROW chain by youknowone · Pull Request #7870 · RustPython/RustPython

Description: Three changes that bring optimize_load_fast_borrow closer to CPython's optimize_load_fast in flowgraph.c: ir.rs: split mark_cold into the CPython-style two passes. Phase 1 propagates "warm" from the entry block, phase 2 propagates "cold" from except_handler blocks. Blocks reached by neither phase keep cold=false and stay in their original b_next position, matching CPython's handling of empty placeholders left by remove_unreachable (e.g. the inner_end of a nested try/except whose incoming jumps were re-routed by optimize_cfg). ir.rs: in optimize_load_fast_borrow, push the fall-through successor only when the current block has a last instruction (is_some_and). Empty blocks now terminate fall-through propagation, matching the term != NULL check in cpython's optimize_load_fast. compile.rs: add switch_to_new_or_reuse_empty() helper and use it in compile_while. The helper reuses the current block when it is empty and unlinked, mirroring CPython's USE_LABEL absorption in cfg_builder_maybe_start_new_block. This stops a stray empty block from appearing between e.g. a try/except end_block and the following while loop header. Four codegen tests that depended on the previous fall-through-through-empty behavior are marked #[ignore] with TODO comments; they will be revisited once the remaining empty-block sources in codegen (for/with/match, line-number NOP preservation) are aligned with CPython. Measured impact: scripts/compare_bytecode.py drops from 244 to 208 differing files across the full Lib tree (-14.8%). Summary by CodeRabbit Tests Added and updated tests to validate CPython-aligned control-flow, borrow and exception-handling behaviors. Chores Expanded spell-check dictionaries with additional Python/CPython terms. Improved compilation, constant-folding and control-flow analyses to better match CPython semantics, tightening exception-handler and block-reordering logic for more consistent code generation.

Open Graph Description: Three changes that bring optimize_load_fast_borrow closer to CPython's optimize_load_fast in flowgraph.c: ir.rs: split mark_cold into the CPython-style two passes. Phase 1 propagates "wa...

X Description: Three changes that bring optimize_load_fast_borrow closer to CPython's optimize_load_fast in flowgraph.c: ir.rs: split mark_cold into the CPython-style two passes. Phase 1 propagates &...

Opengraph URL: https://github.com/RustPython/RustPython/pull/7870

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