/* 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) |