[llvm] [RISCV][VLOPT] Fix operand check in isVectorOpUsedAsScalarOp (PR #112253)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> I think the passthru will need to preserve all elements so I haven't included it.

I am seeing this from the spec:
> The other elements in the destination vector register ( 0 < index < VLEN/SEW) are considered the tail and are managed with the current tail agnostic/undisturbed policy.

IIUC, I think this is saying we only need to preserve elements of the passthru depending on tail policy. I think we could maybe treat the destination as a scalar operand if the policy is TA?

https://github.com/llvm/llvm-project/pull/112253