Regex UpdateBumpalong logic should be applicable to lazy loops as well

[stephentoub]

The optimization we employ in RegexNode.FinalOptimize to insert an UpdateBumpalong node after a starting loop does so for unbounded {One/Notone/Set}loop{atomic} nodes, but not for {One/Notone/Set}lazy nodes.

runtime/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexNode.cs

Lines 396 to 401 in 12a8819

	case Oneloop when node.N == int.MaxValue:
	case Oneloopatomic when node.N == int.MaxValue:
	case Notoneloop when node.N == int.MaxValue:
	case Notoneloopatomic when node.N == int.MaxValue:
	case Setloop when node.N == int.MaxValue:
	case Setloopatomic when node.N == int.MaxValue:

It should be applicable for lazy loops as well, as if the match ends up failing, we will have explored the same range, just effectively in the opposite direction. One thing that may need more thought is if we need to special-case not applying this for atomic lazy loops, which will always only check for the minimum bound.

(This code, and other code in RegexNode, can also be cleaned up nicely now that we have improved C# pattern matching support.)

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Issue Details

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The optimization we employ in RegexNode.FinalOptimize to insert an UpdateBumpalong node after a starting loop does so for unbounded {One/Notone/Set}loop{atomic} nodes, but not for {One/Notone/Set}lazy nodes.

runtime/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexNode.cs

Lines 396 to 401 in 12a8819

	case Oneloop when node.N == int.MaxValue:
	case Oneloopatomic when node.N == int.MaxValue:
	case Notoneloop when node.N == int.MaxValue:
	case Notoneloopatomic when node.N == int.MaxValue:
	case Setloop when node.N == int.MaxValue:
	case Setloopatomic when node.N == int.MaxValue:

It should be applicable for lazy loops as well, as if the match ends up failing, we will have explored the same range, just effectively in the opposite direction. One thing that may need more thought is if we need to special-case not applying this for atomic lazy loops, which will always only check for the minimum bound.

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