[llvm] [RISCV][GISEL] Legalize G_INSERT_SUBVECTOR and G_EXTRACT_SUBVECTOR for scalable vectors (PR #108220)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> Title is wrong, this is not handling G_INSERT_SUBVECTOR or G_EXTRACT_SUBVECTOR. This only handles G_INSERT / G_EXTRACT

Title is right, code is wrong. I implemented the logic of G_INSERT_SUBVECTOR and G_EXTRACT_SUBVECTOR for G_INSERT and G_EXTRACT by accident. Working on a fix. I think this should assuage the concern of wanting to remove G_INSERT and G_EXTRACT. My other patch that is stacked on this should be using G_INSERT_SUBVECTOR and G_EXTRACT_SUBVECTOR too.

https://github.com/llvm/llvm-project/pull/108220