Fix regexp performance regression for patterns starting with s/k#174
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nobu wants to merge 1 commit intok-takata:masterfrom
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Fix regexp performance regression for patterns starting with s/k#174nobu wants to merge 1 commit intok-takata:masterfrom
nobu wants to merge 1 commit intok-takata:masterfrom
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ruby/ruby@981ee02c7c ("Fix performance problem with /k/i and /s/i") was merged for Ruby 4.0 to enable partial Boyer-Moore optimization for patterns containing 's' or 'k' by using the prefix before those characters. However, when 's' or 'k' appears at the start of a pattern (no usable prefix), set_bm_skip() returns 0 and the code returned early without setting any optimization mode, leaving reg->optimize at ONIG_OPTIMIZE_NONE. This caused up to 30x slowdown for patterns like /slackware/i when matched against strings with non-ASCII characters. This patch keeps the improvement from 981ee02c7c for patterns with 3+ char prefix, while fixing the regression by falling back to ONIG_OPTIMIZE_EXACT_IC with the full pattern when the usable prefix is less than 3 characters. Before: /\bslackware\b/i with non-ASCII string: 2.24 us/op After: /\bslackware\b/i with non-ASCII string: 0.70 us/op (3.2x faster) [Bug #21824](https://bugs.ruby-lang.org/issues/21824)
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Merge from ruby/ruby#15848.