[SCEV] Teach SCEVExpander to use zext nneg when possible (#70815)

zext nneg was recently added to the IR in #67982. Teaching SCEVExpander
to emit nneg when possible is valuable since SCEV may have proved
non-trivial facts about loop bounds which would otherwise be lost when
materializing the value.

GitOrigin-RevId: f8742b8d6a3489dc8974f4166d413a66cb8d9c21
1 file changed