diff options
Diffstat (limited to 'gcc/predict.c')
| -rw-r--r-- | gcc/predict.c | 44 |
1 files changed, 35 insertions, 9 deletions
diff --git a/gcc/predict.c b/gcc/predict.c index de1a141..38b9a5b 100644 --- a/gcc/predict.c +++ b/gcc/predict.c @@ -72,14 +72,23 @@ struct predictor_info const char *name; /* Name used in the debugging dumps. */ int hitrate; /* Expected hitrate used by predict_insn_def call. */ + int flags; }; -#define DEF_PREDICTOR(ENUM, NAME, HITRATE) {NAME, HITRATE}, +/* Use given predictor without Dempster-Shaffer theory if it matches + using first_match heuristics. */ +#define PRED_FLAG_FIRST_MATCH 1 + +/* Recompute hitrate in percent to our representation. */ + +#define HITRATE(VAL) ((int)((VAL) * REG_BR_PROB_BASE + 50) / 100) + +#define DEF_PREDICTOR(ENUM, NAME, HITRATE, FLAGS) {NAME, HITRATE, FLAGS}, struct predictor_info predictor_info[] = { #include "predict.def" - /* Upper bound on non-language-specific builtins. */ - {NULL, 0} + /* Upper bound on predictors. */ + {NULL, 0, 0} }; #undef DEF_PREDICTOR @@ -211,6 +220,8 @@ combine_predictions_for_insn (insn, bb) rtx *pnote = ®_NOTES (insn); int best_probability = PROB_EVEN; int best_predictor = END_PREDICTORS; + int combined_probability = REG_BR_PROB_BASE / 2; + int d; if (rtl_dump_file) fprintf (rtl_dump_file, "Predictions for insn %i bb %i\n", INSN_UID (insn), @@ -230,16 +241,33 @@ combine_predictions_for_insn (insn, bb) if (best_predictor > predictor) best_probability = probability, best_predictor = predictor; *pnote = XEXP (*pnote, 1); + + d = (combined_probability * probability + + (REG_BR_PROB_BASE - combined_probability) + * (REG_BR_PROB_BASE - probability)); + /* An FP math to avoid overflows of 32bit integers. */ + combined_probability = (((double)combined_probability) * probability + * REG_BR_PROB_BASE / d + 0.5); } else pnote = &XEXP (*pnote, 1); } + if (predictor_info [best_predictor].flags & PRED_FLAG_FIRST_MATCH) + combined_probability = best_probability; dump_prediction (PRED_FIRST_MATCH, best_probability, bb); + dump_prediction (PRED_COMBINED, combined_probability, bb); if (!prob_note) { REG_NOTES (insn) = gen_rtx_EXPR_LIST (REG_BR_PROB, - GEN_INT (best_probability), REG_NOTES (insn)); + GEN_INT (combined_probability), REG_NOTES (insn)); + /* Save the prediction into CFG in case we are seeing non-degenerated + conditional jump. */ + if (bb->succ->succ_next) + { + BRANCH_EDGE (bb)->probability = combined_probability; + FALLTHRU_EDGE (bb)->probability = REG_BR_PROB_BASE - combined_probability; + } } } @@ -280,7 +308,8 @@ estimate_probability (loops_info) /* Loop branch heruistics - predict as taken an edge back to a loop's head. */ for (e = BASIC_BLOCK(j)->succ; e; e = e->succ_next) - if (e->dest == loops_info->array[i].header) + if (e->dest == loops_info->array[i].header + && e->src == loops_info->array[i].latch) { header_found = 1; predict_edge_def (e, PRED_LOOP_BRANCH, TAKEN); @@ -296,10 +325,7 @@ estimate_probability (loops_info) } } - /* Attempt to predict conditional jumps using a number of heuristics. - For each conditional jump, we try each heuristic in a fixed order. - If more than one heuristic applies to a particular branch, the first - is used as the prediction for the branch. */ + /* Attempt to predict conditional jumps using a number of heuristics. */ for (i = 0; i < n_basic_blocks; i++) { basic_block bb = BASIC_BLOCK (i); |