[llvm] [RISCV] Disable fixed vectors in getOptimalMemOpType if minimum VLEN is 32. (PR #102974)

[Philip Reames via llvm-commits]

preames wrote:

> These PRs #102405 and #102974 will affect the release 19.1.0, maybe can be backport to that release.

I have no particular objection to this being backported, but I do want to clearly note that a minimum VLEN of 32 (i.e. zve32x,vze32f) is not a supported configuration.  There are probably other problems lurking around this area, and I don't want to give anyone the expectation that this is generally expected to work.  At the moment, trying to use zve32x/zve32f is living very dangerously.  

https://github.com/llvm/llvm-project/pull/102974