[llvm] [RISCV][GISEL] Legalize G_PTRMASK (PR #73062)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

> Is this based off another target? I see AArch64 handles this in instruction selection.

I didn’t see why this opcode couldn’t be handled generally for all targets. That sounded like it fit well where I put it. No reason why it needs to be in a target specific instruction selector. Maybe other targets can eventually reuse the generic logic added here. 

https://github.com/llvm/llvm-project/pull/73062