RE: [PATCH RFC v4 net-next 00/26] BPF syscall, maps, verifier, samples, llvm

[David Laight]

From: Of Alexei Starovoitov
> one more RFC...
> 
> Major difference vs previous set is a new 'load 64-bit immediate' eBPF insn.
> Which is first 16-byte instruction. It shows how eBPF ISA can be extended
> while maintaining backward compatibility, but mainly it cleans up eBPF
> program access to maps and improves run-time performance.

Wouldn't it be more sensible to follow the scheme used by a lot of cpus
and add a 'load high' instruction (follow with 'add' or 'or').
It still takes 16 bytes to load a 64bit immediate value, but the instruction
size remains constant.
There is nothing to stop any JIT software detecting the instruction pair.

	David



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