JIT: Consider compressing loop bit vectors further

[jakobbotsch]

Loop bit vectors are stored starting from the postorder index of the header block, since it is known that all descendants have lower postorder numbers. However, if we compute the minimum postorder number of the contained loop blocks, then we can compress the domain further. This will speed up iteration over loop blocks.

See #95326 (comment) for more context

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Issue Details

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Loop bit vectors are stored starting from the postorder index of the header block, since it is known that all descendants have lower postorder numbers. However, if we compute the minimum postorder number of the contained loop blocks, then we can compress the domain further. This will speed up iteration over loop blocks.

See #95326 (comment) for more context

Author:	jakobbotsch
Assignees:	jakobbotsch
Labels:	area-CodeGen-coreclr
Milestone:	-