Regex compiler / source generator can use IndexOf to speed up lazy loop

[stephentoub]

In greedy char loops, if the loop is followed by a known literal, when backtracking we LastIndexOf to find the next possible place to try to continue the match, rather than just backing up one char at a time. We can do the opposite for lazy char loops: rather than incrementing the position one char at a time, we can IndexOf{Any} for the following literal to find the next possible place to continue matching. In the case of a .? in Singleline, we can use IndexOf for the subsequent literal; in the case of a .? when not in Singeline, we can use IndexOfAny('\n', literal).

[ghost]

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Issue Details

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In greedy char loops, if the loop is followed by a known literal, when backtracking we LastIndexOf to find the next possible place to try to continue the match, rather than just backing up one char at a time. We can do the opposite for lazy char loops: rather than incrementing the position one char at a time, we can IndexOf for the following literal to find the next possible place to continue matching.

Author:	stephentoub
Assignees:	-
Labels:	area-System.Text.RegularExpressions, tenet-performance
Milestone:	7.0.0