perf(parser): remove branch from parse_modifiers

[overlookmotel]

Small perf optimization.

Modifiers already encodes which modifiers have been seen, so there's no need to additionally track whether a static modifier has been seen or not in a separate variable.

Remove has_seen_static_modifier variable from parse_modifiers, and the unpredictable branch which updates it, and instead do the check only when it's needed in try_parse_modifier.

+0.1% improvement on some parser benchmarks, and CodSpeed doesn't take into account the cost of branch misprediction.

[overlookmotel]

• perf(parser): defer calculation of Modifier spans #20823 : 2 dependent PRs (#20824 , #20826 )
• perf(parser): remove branch from parse_modifiers #20821 👈 (View in Graphite)
• perf(parser): reduce Kind to ModifierKind conversions in eat_modifiers_before_declaration #20820
• refactor(parser): shorten code handling illegal modifiers #20781
• perf(parser): fast path for no syntax errors when checking modifiers #20748
• perf(parser): remove a lookahead from eat_modifiers_before_declaration #20755
• refactor(parser): nest modifiers types in modules #20754
• refactor(parser): re-order modifiers code #20753
• perf(parser): store Modifiers on stack #20742
• perf(parser): add Modifiers::get method #20741
• refactor(parser): rename ModifierKinds::empty to none #20740
• refactor(parser): rename ModifierFlags to ModifierKinds #20739
• refactor(parser): simplify ModifierFlags #20738
• refactor(parser): import from std at top level #20737
• refactor(parser): remove Modifier::is_static() #20736
• refactor(parser): remove dead code from modifier parsing #20735
• main

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[Copilot]

Pull request overview

This PR applies a small hot-path optimization in the parser’s modifier parsing by removing a dedicated has_seen_static_modifier tracking branch and relying on the existing ModifierKinds bitfield already stored in Modifiers.

Changes:

• Remove has_seen_static_modifier from parse_modifiers.
• Pass the already-seen ModifierKinds into try_parse_modifier and use it to detect repeated static.

[codspeed-hq]

Merging this PR will not alter performance

✅ 48 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing om/03-28-perf_parser_remove_branch_from_parse_modifiers_ (2e7e6bd) with main (eb02c88)²}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (2e7e6bd) during the generation of this report, so eb02c88 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[camc314]

Merge activity

• Mar 29, 3:31 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Mar 29, 3:40 PM UTC: The Graphite merge queue removed this pull request due to removal of a downstack PR #20820.
• Mar 29, 3:40 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Mar 29, 3:41 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Mar 29, 3:41 PM UTC: The merge label '0-merge' was removed. This PR will no longer be merged by the Graphite merge queue
• Mar 29, 3:41 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Mar 29, 4:19 PM UTC: The Graphite merge queue removed this pull request due to downstack failures on PR #20820.
• Mar 29, 4:40 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Mar 29, 4:41 PM UTC: camc314 added this pull request to the Graphite merge queue.
• Mar 29, 4:42 PM UTC: Merged by the Graphite merge queue.