[llvm] [LV] Ignore user-specified interleave count when unsafe. (PR #153009)

[Kerry McLaughlin via llvm-commits]

kmclaughlin-arm wrote:

This PR fixes an issue I found whilst testing #147535 with LNT.
When built with `--force-vector-interleave=4`, the s1221 loop in LoopRestructuring-flt fails as it does not match the reference result.

https://github.com/llvm/llvm-project/pull/153009