| /* Definitions for the branch prediction routines in the GNU compiler. |
| Copyright (C) 2001-2013 Free Software Foundation, Inc. |
| |
| This file is part of GCC. |
| |
| GCC is free software; you can redistribute it and/or modify it under |
| the terms of the GNU General Public License as published by the Free |
| Software Foundation; either version 3, or (at your option) any later |
| version. |
| |
| GCC is distributed in the hope that it will be useful, but WITHOUT ANY |
| WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GCC; see the file COPYING3. If not see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* Before including this file, you should define a macro: |
| |
| DEF_PREDICTOR (ENUM, NAME, HITRATE) |
| |
| This macro will be called once for each predictor. The ENUM will |
| be of type `enum predictor', and will enumerate all supported |
| predictors. The order of DEF_PREDICTOR calls is important, as |
| in the first match combining heuristics, the predictor appearing |
| first in this file will win. |
| |
| NAME is used in the debugging output to determine predictor type. |
| |
| HITRATE is the probability that edge predicted by predictor as taken |
| will be really taken (so it should be always above |
| REG_BR_PROB_BASE / 2). */ |
| |
| |
| /* A value used as final outcome of all heuristics. */ |
| DEF_PREDICTOR (PRED_COMBINED, "combined", PROB_ALWAYS, 0) |
| |
| /* An outcome estimated by Dempster-Shaffer theory. */ |
| DEF_PREDICTOR (PRED_DS_THEORY, "DS theory", PROB_ALWAYS, 0) |
| |
| /* A combined heuristics using probability determined by first |
| matching heuristics from this list. */ |
| DEF_PREDICTOR (PRED_FIRST_MATCH, "first match", PROB_ALWAYS, 0) |
| |
| /* Heuristic applying when no heuristic below applies. */ |
| DEF_PREDICTOR (PRED_NO_PREDICTION, "no prediction", PROB_ALWAYS, 0) |
| |
| /* Mark unconditional jump as taken. */ |
| DEF_PREDICTOR (PRED_UNCONDITIONAL, "unconditional jump", PROB_ALWAYS, |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Use number of loop iterations determined by # of iterations |
| analysis to set probability. We don't want to use Dempster-Shaffer |
| theory here, as the predictions is exact. */ |
| DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS, |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Hints dropped by user via __builtin_expect feature. */ |
| DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY, |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Use number of loop iterations guessed by the contents of the loop. */ |
| DEF_PREDICTOR (PRED_LOOP_ITERATIONS_GUESSED, "guessed loop iterations", |
| PROB_ALWAYS, PRED_FLAG_FIRST_MATCH) |
| |
| /* Branch containing goto is probably not taken. */ |
| DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (50), 0) |
| |
| /* Branch to basic block containing call marked by noreturn attribute. */ |
| DEF_PREDICTOR (PRED_NORETURN, "noreturn call", PROB_VERY_LIKELY, |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Branch to basic block containing call marked by cold function attribute. */ |
| DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", PROB_VERY_LIKELY, |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Loopback edge is taken. */ |
| DEF_PREDICTOR (PRED_LOOP_BRANCH, "loop branch", HITRATE (86), |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Edge causing loop to terminate is probably not taken. */ |
| DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (91), |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Pointers are usually not NULL. */ |
| DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (85), 0) |
| DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (85), 0) |
| |
| /* NE is probable, EQ not etc... */ |
| DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (79), 0) |
| DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (71), 0) |
| DEF_PREDICTOR (PRED_FPOPCODE, "fp_opcode", HITRATE (90), 0) |
| DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)", HITRATE (73), 0) |
| DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", HITRATE (72), 0) |
| DEF_PREDICTOR (PRED_TREE_FPOPCODE, "fp_opcode (on trees)", HITRATE (90), 0) |
| |
| /* Branch guarding call is probably taken. */ |
| DEF_PREDICTOR (PRED_CALL, "call", HITRATE (71), 0) |
| |
| /* Branch causing function to terminate is probably not taken. */ |
| DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (61), 0) |
| |
| /* Branch containing goto is probably not taken. */ |
| DEF_PREDICTOR (PRED_GOTO, "goto", HITRATE (70), 0) |
| |
| /* Branch ending with return constant is probably not taken. */ |
| DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (67), 0) |
| |
| /* Branch ending with return negative constant is probably not taken. */ |
| DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (96), 0) |
| |
| /* Branch ending with return; is probably not taken */ |
| DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (90), 0) |
| |
| /* Branches to a mudflap bounds check are extremely unlikely. */ |
| DEF_PREDICTOR (PRED_MUDFLAP, "mudflap check", PROB_VERY_LIKELY, 0) |
| |
| /* Branches to compare induction variable to a loop bound is |
| extremely likely. */ |
| DEF_PREDICTOR (PRED_LOOP_IV_COMPARE_GUESS, "guess loop iv compare", |
| PROB_VERY_LIKELY, 0) |
| |
| /* Use number of loop iterations determined by # of iterations analysis |
| to set probability of branches that compares IV to loop bound variable. */ |
| DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_VERY_LIKELY, |
| PRED_FLAG_FIRST_MATCH) |
| |
| /* Branches to hot labels are likely. */ |
| DEF_PREDICTOR (PRED_HOT_LABEL, "hot label", HITRATE (85), 0) |
| |
| /* Branches to cold labels are extremely unlikely. */ |
| DEF_PREDICTOR (PRED_COLD_LABEL, "cold label", PROB_VERY_LIKELY, |
| PRED_FLAG_FIRST_MATCH) |
