Re: [PATCH bpf-next v4 3/5] bpf: Inline calls to bpf_loop when callback is known

[Eduard Zingerman <eddyz87@gmail.com>]

> On Fri, 2022-06-10 at 16:01 -0700, Song Liu wrote:
> 
> In this case, we need to initialize fit_for_inline to true, no?

You are right...

My Last try is below, if you don't like it I'll proceed with your
version.  I just really don't like the "not-cannot" part in the
expression "!inline_state->cannot_inline" :)

static void update_loop_inline_state(struct bpf_verifier_env *env, u32 subprogno)
{
	struct bpf_loop_inline_state *state = &cur_aux(env)->loop_inline_state;
	struct bpf_reg_state *regs = cur_regs(env);
	struct bpf_reg_state *flags_reg = &regs[BPF_REG_4];
	int flags_is_zero =
		register_is_const(flags_reg) && flags_reg->var_off.value == 0;

	if (!state->initialized) {
		state->initialized = 1;
		state->fit_for_inline = flags_is_zero;
		state->callback_subprogno = subprogno;
		return;
	}

	if (!state->fit_for_inline)
		return;

	state->fit_for_inline =
		flags_is_zero &&
		state->callback_subprogno == subprogno;
}

static int optimize_bpf_loop(struct bpf_verifier_env *env)
{
	// ...
	if (is_bpf_loop_call(insn) && inline_state->fit_for_inline) { ... }
	// ...
}

Thanks,
Eduard