ok for google branches.
David
On Thu, Feb 2, 2012 at 2:30 PM, Rong Xu <x...@google.com> wrote:
> Hi,
>
> This patch curbs the counter scaling factor that causing counter
> overflow in inline transformation. The negavie counter triggers
> a later pass assertion.
>
> Tested: inertnal performance benchmarks.
>
> -Rong
>
> 2012-02-02 Rong Xu <x...@google.com>
>
> * tree-inline.c (copy_cfg_body): Curb the scaling factor to
> avoid counter overflow.
>
> Index: tree-inline.c
> ===================================================================
> --- tree-inline.c (revision 183768)
> +++ tree-inline.c (working copy)
> @@ -2198,8 +2198,49 @@
> gcov_type incoming_count = 0;
>
> if (ENTRY_BLOCK_PTR_FOR_FUNCTION (src_cfun)->count)
> - count_scale = (REG_BR_PROB_BASE * (double)count
> - / ENTRY_BLOCK_PTR_FOR_FUNCTION (src_cfun)->count);
> + {
> + struct cgraph_node *node = cgraph_node (callee_fndecl);
> + double f_max;
> + gcov_type max_count_scale;
> + gcov_type callee_max_bb_cnt;
> + gcov_type max_value = ((gcov_type) 1 << ((sizeof(gcov_type) * 8) - 1));
> + max_value = ~max_value;
> + count_scale = (REG_BR_PROB_BASE * (double)count
> + / ENTRY_BLOCK_PTR_FOR_FUNCTION (src_cfun)->count);
> +
> + /* Reducing the scaling factor when it can cause counter overflow.
> + This can happen for comdat functions where the counters are split.
> + It's more likely for recursive inlines. */
> + gcc_assert (node);
> + callee_max_bb_cnt = node->max_bb_count;
> +
> + if (callee_max_bb_cnt == 0)
> + {
> + gcov_type c = ENTRY_BLOCK_PTR_FOR_FUNCTION (src_cfun)->count;
> +
> + FOR_EACH_BB_FN (bb, src_cfun)
> + if (bb->count > node->max_bb_count)
> + callee_max_bb_cnt = node->max_bb_count;
> +
> + if (c > callee_max_bb_cnt)
> + callee_max_bb_cnt = c;
> +
> + node->max_bb_count = callee_max_bb_cnt;
> + }
> +
> + f_max = (double) max_value * REG_BR_PROB_BASE / callee_max_bb_cnt - 1;
> + if (f_max > max_value)
> + max_count_scale = max_value;
> + else
> + max_count_scale = f_max;
> +
> + if (count_scale > max_count_scale)
> + {
> + if (flag_opt_info >= OPT_INFO_MED)
> + warning (0, "Reducing scaling factor to avoid counter
> overflow.");
> + count_scale = max_count_scale;
> + }
> + }
> else
> count_scale = REG_BR_PROB_BASE;
>
> @@ -2221,7 +2262,7 @@
> incoming_frequency += EDGE_FREQUENCY (e);
> incoming_count += e->count;
> }
> - incoming_count = incoming_count * count_scale / REG_BR_PROB_BASE;
> + incoming_count = ((double) incoming_count) * count_scale /
> REG_BR_PROB_BASE;
> incoming_frequency
> = incoming_frequency * frequency_scale / REG_BR_PROB_BASE;
> ENTRY_BLOCK_PTR->count = incoming_count;
>
> --
> This patch is available for review at http://codereview.appspot.com/5622052
