gh-153568: Stop re-walking memo lists when growing left-recursive rules#153574
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pablogsal wants to merge 1 commit into
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gh-153568: Stop re-walking memo lists when growing left-recursive rules#153574pablogsal wants to merge 1 commit into
pablogsal wants to merge 1 commit into
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…ve rules The left-recursion driver now keeps a direct reference to its memo entry and updates it in place on every iteration.
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The grow-the-seed loop of every left-recursive rule searched the token's memo list on each iteration to update its own entry, even though it inserted that entry itself on the first pass. Keeping a direct reference and writing through it removes the repeated walks.
Benchmark (parsing 8 of the largest stdlib files, 1.3 MB, 20 times per run with
_PyParser_ASTFromString— parser only, no AST-to-Python conversion; pyperf, interleaved runs):On its own the effect is below measurement noise; combined with the memo filter of #153571 it measured about 3% because the remaining walks there are the long ones this change removes.