Hi, profile updating in tail merging is completely wrong when profile feedback is missing or 0. This fixes it hopefully reasonably. Bootstrapped/regtested x86_64-linux.
Honza * tree-ssa-tail-merge.c (replace_block_by): Fix profile updating. Index: tree-ssa-tail-merge.c =================================================================== --- tree-ssa-tail-merge.c (revision 249244) +++ tree-ssa-tail-merge.c (working copy) @@ -1555,29 +1555,51 @@ replace_block_by (basic_block bb1, basic pred_edge, UNKNOWN_LOCATION); } - bb2->frequency += bb1->frequency; - if (bb2->frequency > BB_FREQ_MAX) - bb2->frequency = BB_FREQ_MAX; - bb2->count += bb1->count; /* Merge the outgoing edge counts from bb1 onto bb2. */ profile_count out_sum = profile_count::zero (); + int out_freq_sum = 0; + + /* Recompute the edge probabilities from the new merged edge count. + Use the sum of the new merged edge counts computed above instead + of bb2's merged count, in case there are profile count insanities + making the bb count inconsistent with the edge weights. */ + FOR_EACH_EDGE (e1, ei, bb1->succs) + { + if (e1->count.initialized_p ()) + out_sum += e1->count; + out_freq_sum += EDGE_FREQUENCY (e1); + } + FOR_EACH_EDGE (e1, ei, bb2->succs) + { + if (e1->count.initialized_p ()) + out_sum += e1->count; + out_freq_sum += EDGE_FREQUENCY (e1); + } + FOR_EACH_EDGE (e1, ei, bb1->succs) { e2 = find_edge (bb2, e1->dest); gcc_assert (e2); e2->count += e1->count; + if (out_sum > 0 && e2->count.initialized_p ()) + { + e2->probability = e2->count.probability_in (bb2->count); + } + else if (bb1->frequency && bb2->frequency) + e2->probability = e1->probability; + else if (bb2->frequency && !bb1->frequency) + ; + else if (out_freq_sum) + e2->probability = GCOV_COMPUTE_SCALE (EDGE_FREQUENCY (e1) + + EDGE_FREQUENCY (e2), + out_freq_sum); out_sum += e2->count; } - /* Recompute the edge probabilities from the new merged edge count. - Use the sum of the new merged edge counts computed above instead - of bb2's merged count, in case there are profile count insanities - making the bb count inconsistent with the edge weights. */ - FOR_EACH_EDGE (e2, ei, bb2->succs) - { - e2->probability = e2->count.probability_in (out_sum); - } + bb2->frequency += bb1->frequency; + if (bb2->frequency > BB_FREQ_MAX) + bb2->frequency = BB_FREQ_MAX; /* Move over any user labels from bb1 after the bb2 labels. */ gimple_stmt_iterator gsi1 = gsi_start_bb (bb1);