diff options
Diffstat (limited to 'gcc/cfg.c')
| -rw-r--r-- | gcc/cfg.c | 61 |
1 files changed, 61 insertions, 0 deletions
@@ -888,3 +888,64 @@ brief_dump_cfg (FILE *file) dump_cfg_bb_info (file, bb); } } + +/* An edge originally destinating BB of FREQUENCY and COUNT has been proved to + leave the block by TAKEN_EDGE. Update profile of BB such that edge E can be + redirected to destiantion of TAKEN_EDGE. + + This function may leave the profile inconsistent in the case TAKEN_EDGE + frequency or count is believed to be lower than FREQUENCY or COUNT + respectivly. */ +void +update_bb_profile_for_threading (basic_block bb, int edge_frequency, + gcov_type count, edge taken_edge) +{ + edge c; + int prob; + + bb->count -= count; + if (bb->count < 0) + bb->count = 0; + + /* Compute the probability of TAKEN_EDGE being reached via threaded edge. + Watch for overflows. */ + if (bb->frequency) + prob = edge_frequency * REG_BR_PROB_BASE / bb->frequency; + else + prob = 0; + if (prob > taken_edge->probability) + { + if (dump_file) + fprintf (dump_file, "Jump threading proved probability of edge " + "%i->%i too small (it is %i, should be %i).\n", + taken_edge->src->index, taken_edge->dest->index, + taken_edge->probability, prob); + prob = taken_edge->probability; + } + + /* Now rescale the probabilities. */ + taken_edge->probability -= prob; + prob = REG_BR_PROB_BASE - prob; + bb->frequency -= edge_frequency; + if (bb->frequency < 0) + bb->frequency = 0; + if (prob <= 0) + { + if (dump_file) + fprintf (dump_file, "Edge frequencies of bb %i has been reset, " + "frequency of block should end up being 0, it is %i\n", + bb->index, bb->frequency); + bb->succ->probability = REG_BR_PROB_BASE; + for (c = bb->succ->succ_next; c; c = c->succ_next) + c->probability = 0; + } + else + for (c = bb->succ; c; c = c->succ_next) + c->probability = ((c->probability * REG_BR_PROB_BASE) / (double) prob); + + if (bb != taken_edge->src) + abort (); + taken_edge->count -= count; + if (taken_edge->count < 0) + taken_edge->count = 0; +} |