Re: [PATCH 12/19] target/ppc/pmu_book3s_helper.c: enable PMC1 counter negative EBB

[Richard Henderson]

On 8/14/21 9:13 AM, Daniel Henrique Barboza wrote:
> https://github.com/torvalds/linux/blob/master/tools/testing/selftests/powerpc/pmu/count_instructions.c 
>
>
> This test runs an instruction loop that consists of 'addi' instructions . Before running 
> the instructions
> there's an overhead calculation with an empty loop.
...
> static void ppc_tr_tb_stop(DisasContextBase *dcbase, CPUState *cs)
>       target_ulong nip = ctx->base.pc_next;
>       int sse;
>
> +    gen_helper_insns_inc(cpu_env, tcg_constant_i32(dcbase->num_insns));
> +
>       if (is_jmp == DISAS_NORETURN) {
>           /* We have already exited the TB. */
>           return;

You've not considered how branches are implemented.

We generate code to exit the tb in gen_bcond.  Anything you emit after that is 
dead code.


r~