Is there a need to have 10 iterations of early inline for autofdo?
David
On Thu, Nov 13, 2014 at 2:25 PM, Dehao Chen <de...@google.com> wrote:
> In AutoFDO, we increase einline iterations. This could lead to
> extensive code bloat if we have recursive calls like:
>
> dtor() {
> destroy(node);
> }
>
> destroy(node) {
> destroy(left)
> destroy(right)
> }
>
> In this case, the size growth will be around 8 which is smaller than
> threshold (11). However, if we allow this to happen for 2 iterations,
> it will expand the size by 1024X. To fix this problem, we want to set
> a much smaller threshold in the AutoFDO case. This is because AutoFDO
> do not not rely on aggressive einline to gain more profile context.
>
> And also, in AutoFDO pass, after we processed a function, we need to
> recompute inline parameters because rebuild_cgraph_edges will zero out
> all inline parameters.
>
> The patch is attached below, bootstrapped and perf test on-going. OK
> for google-4_9?
>
> Thanks,
> Dehao
>
> Index: gcc/auto-profile.c
> ===================================================================
> --- gcc/auto-profile.c (revision 217523)
> +++ gcc/auto-profile.c (working copy)
> @@ -1771,6 +1771,7 @@ auto_profile (void)
> free_dominance_info (CDI_DOMINATORS);
> free_dominance_info (CDI_POST_DOMINATORS);
> rebuild_cgraph_edges ();
> + compute_inline_parameters (cgraph_get_node
> (current_function_decl), true);
> pop_cfun ();
> }
>
> Index: gcc/opts.c
> ===================================================================
> --- gcc/opts.c (revision 217523)
> +++ gcc/opts.c (working copy)
> @@ -1853,6 +1853,12 @@ common_handle_option (struct gcc_options *opts,
> maybe_set_param_value (
> PARAM_EARLY_INLINER_MAX_ITERATIONS, 10,
> opts->x_param_values, opts_set->x_param_values);
> + maybe_set_param_value (
> + PARAM_EARLY_INLINING_INSNS, 4,
> + opts->x_param_values, opts_set->x_param_values);
> + maybe_set_param_value (
> + PARAM_EARLY_INLINING_INSNS_COMDAT, 4,
> + opts->x_param_values, opts_set->x_param_values);
> value = true;
> /* No break here - do -fauto-profile processing. */
> case OPT_fauto_profile:
