Re: [PATCH bpf-next] bpf: arm64: Redefine MOV consistent with arch insn

[Will Deacon]

On Tue, Mar 30, 2021 at 03:42:35PM +0800, Jianlin Lv wrote:
> A64_MOV is currently mapped to Add Instruction. Architecturally MOV
> (register) is an alias of ORR (shifted register) and MOV (to or from SP)
> is an alias of ADD (immediate).
> This patch redefines A64_MOV and uses existing functionality
> aarch64_insn_gen_move_reg() in insn.c to encode MOV (register) instruction.
> For moving between register and stack pointer, rename macro to A64_MOV_SP.

What does this gain us? There's no requirement for a BPF "MOV" to match an
arm64 architectural "MOV", so what's the up-side of aligning them like this?

Cheers,

Will