[llvm] [VectorCombine] Use isSafeToSpeculativelyExecute to guard VP scalarization (PR #69494)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

Should we be able to speculate functions like `sdiv_nxv1i64_anymask`? It looks like we know that the divisor is non-zero. You call this out in the PR description but it does not seem to be supported:

> This also allows speculation in more cases, e.g. when the divisor is known to be non-zero.

https://github.com/llvm/llvm-project/pull/69494