[llvm] [RISCV][GISEL] Add IRTranslation for shufflevector on scalable vector types (PR #80378)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> How would you otherwise distinguish between integer and float splats? If a splat vector only gets an immediate?

How do we distinguish today between integers and floats for G_SHUFFLE_VECTOR? We don't have a G_FSHUFFLE_VECTOR.

My guess would be `G_SPLAT_VECTOR (G_CONSTANT 8)` vs `G_SPLAT_VECTOR (G_FCONSTANT 3.2)` allows us to look into the operand and determine whether it is a float or not.

https://github.com/llvm/llvm-project/pull/80378