Iteratively parse nested parentheses in PrattParserWorker - #2278
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Replace the lookahead-based grouping parentheses counter (`CountGroupingParentheses`) with a bottom-up iterative approach in `PrattParserWorker::ParsePrimary()` to eliminate quadratic $O(N^2)$ lookahead scans while keeping $O(1)$ call-stack frames on deeply nested parenthesized expressions. ### Benchmarks (`pratt_parser_benchmark`, `-c opt --dynamic_mode=off`) | Benchmark Case | Before (Mean) | After (Mean) | Change / Speedup | | :--- | ---: | ---: | ---: | | `BM_Pratt_ParseNestedParentheses/10` | 724 ns | 535 ns | -26.1% (1.35x faster) | | `BM_Pratt_ParseNestedParentheses/50` | 2,484 ns | 1,625 ns | -34.6% (1.53x faster) | | `BM_Pratt_ParseNestedParentheses/200` | 8,859 ns | 5,427 ns | -38.7% (1.63x faster) | | `BM_Pratt_ParseNestedLeftParenthesesCalc/10` | 7,876 ns | 3,397 ns | -56.9% (2.32x faster) | | `BM_Pratt_ParseNestedLeftParenthesesCalc/50` | 112,539 ns | 14,518 ns | -87.1% (7.75x faster) | | `BM_Pratt_ParseNestedLeftParenthesesCalc/200` | 1,583,442 ns | 57,375 ns | -96.4% (27.6x faster) | PiperOrigin-RevId: 987017594
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Iteratively parse nested parentheses in PrattParserWorker
Replace the lookahead-based grouping parentheses counter ($O(N^2)$ lookahead scans while keeping $O(1)$ call-stack frames on deeply nested parenthesized expressions.
CountGroupingParentheses) with a bottom-up iterative approach inPrattParserWorker::ParsePrimary()to eliminate quadraticBenchmarks (
pratt_parser_benchmark,-c opt --dynamic_mode=off)BM_Pratt_ParseNestedParentheses/10BM_Pratt_ParseNestedParentheses/50BM_Pratt_ParseNestedParentheses/200BM_Pratt_ParseNestedLeftParenthesesCalc/10BM_Pratt_ParseNestedLeftParenthesesCalc/50BM_Pratt_ParseNestedLeftParenthesesCalc/200