Hari Limaye 3bf83e3866 [LoopIdiom] Reland: Support 'shift until less-than' idiom #95002 (#98298) ...

The original patch failed to handle the case where the loopback
condition compared against a constant exceeding 64 bit unsigned range -
which caused a buildbot failure.

This PR fixes this and relands the original PR #95002.

The current loop idiom code for recognising and inserting a CTLZ
intrinsic does not support loops where the loopback control is based on
an unsigned less-than condition. This patch adds support for recognising
these loops and inserting a CTLZ intrinsic.

Fixes the missed optimization cases in #51064.

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Co-authored-by: David Sherwood <david.sherwood@arm.com>

2024-07-16 13:58:07 +01:00

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