| 1 |
684 |
jeremybenn |
/* Definitions for the branch prediction routines in the GNU compiler.
|
| 2 |
|
|
Copyright (C) 2001, 2003, 2004, 2007, 2008 Free Software Foundation, Inc.
|
| 3 |
|
|
|
| 4 |
|
|
This file is part of GCC.
|
| 5 |
|
|
|
| 6 |
|
|
GCC is free software; you can redistribute it and/or modify it under
|
| 7 |
|
|
the terms of the GNU General Public License as published by the Free
|
| 8 |
|
|
Software Foundation; either version 3, or (at your option) any later
|
| 9 |
|
|
version.
|
| 10 |
|
|
|
| 11 |
|
|
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
|
| 12 |
|
|
WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
| 13 |
|
|
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
| 14 |
|
|
for more details.
|
| 15 |
|
|
|
| 16 |
|
|
You should have received a copy of the GNU General Public License
|
| 17 |
|
|
along with GCC; see the file COPYING3. If not see
|
| 18 |
|
|
. */
|
| 19 |
|
|
|
| 20 |
|
|
/* Before including this file, you should define a macro:
|
| 21 |
|
|
|
| 22 |
|
|
DEF_PREDICTOR (ENUM, NAME, HITRATE)
|
| 23 |
|
|
|
| 24 |
|
|
This macro will be called once for each predictor. The ENUM will
|
| 25 |
|
|
be of type `enum predictor', and will enumerate all supported
|
| 26 |
|
|
predictors. The order of DEF_PREDICTOR calls is important, as
|
| 27 |
|
|
in the first match combining heuristics, the predictor appearing
|
| 28 |
|
|
first in this file will win.
|
| 29 |
|
|
|
| 30 |
|
|
NAME is used in the debugging output to determine predictor type.
|
| 31 |
|
|
|
| 32 |
|
|
HITRATE is the probability that edge predicted by predictor as taken
|
| 33 |
|
|
will be really taken (so it should be always above
|
| 34 |
|
|
REG_BR_PROB_BASE / 2). */
|
| 35 |
|
|
|
| 36 |
|
|
|
| 37 |
|
|
/* A value used as final outcome of all heuristics. */
|
| 38 |
|
|
DEF_PREDICTOR (PRED_COMBINED, "combined", PROB_ALWAYS, 0)
|
| 39 |
|
|
|
| 40 |
|
|
/* An outcome estimated by Dempster-Shaffer theory. */
|
| 41 |
|
|
DEF_PREDICTOR (PRED_DS_THEORY, "DS theory", PROB_ALWAYS, 0)
|
| 42 |
|
|
|
| 43 |
|
|
/* A combined heuristics using probability determined by first
|
| 44 |
|
|
matching heuristics from this list. */
|
| 45 |
|
|
DEF_PREDICTOR (PRED_FIRST_MATCH, "first match", PROB_ALWAYS, 0)
|
| 46 |
|
|
|
| 47 |
|
|
/* Heuristic applying when no heuristic below applies. */
|
| 48 |
|
|
DEF_PREDICTOR (PRED_NO_PREDICTION, "no prediction", PROB_ALWAYS, 0)
|
| 49 |
|
|
|
| 50 |
|
|
/* Mark unconditional jump as taken. */
|
| 51 |
|
|
DEF_PREDICTOR (PRED_UNCONDITIONAL, "unconditional jump", PROB_ALWAYS,
|
| 52 |
|
|
PRED_FLAG_FIRST_MATCH)
|
| 53 |
|
|
|
| 54 |
|
|
/* Use number of loop iterations determined by # of iterations
|
| 55 |
|
|
analysis to set probability. We don't want to use Dempster-Shaffer
|
| 56 |
|
|
theory here, as the predictions is exact. */
|
| 57 |
|
|
DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS,
|
| 58 |
|
|
PRED_FLAG_FIRST_MATCH)
|
| 59 |
|
|
|
| 60 |
|
|
/* Hints dropped by user via __builtin_expect feature. */
|
| 61 |
|
|
DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY,
|
| 62 |
|
|
PRED_FLAG_FIRST_MATCH)
|
| 63 |
|
|
|
| 64 |
|
|
/* Use number of loop iterations guessed by the contents of the loop. */
|
| 65 |
|
|
DEF_PREDICTOR (PRED_LOOP_ITERATIONS_GUESSED, "guessed loop iterations",
|
| 66 |
|
|
PROB_ALWAYS, PRED_FLAG_FIRST_MATCH)
|
| 67 |
|
|
|
| 68 |
|
|
/* Branch containing goto is probably not taken. */
|
| 69 |
|
|
DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (50), 0)
|
| 70 |
|
|
|
| 71 |
|
|
/* Branch to basic block containing call marked by noreturn attribute. */
|
| 72 |
|
|
DEF_PREDICTOR (PRED_NORETURN, "noreturn call", PROB_VERY_LIKELY,
|
| 73 |
|
|
PRED_FLAG_FIRST_MATCH)
|
| 74 |
|
|
|
| 75 |
|
|
/* Branch to basic block containing call marked by cold function attribute. */
|
| 76 |
|
|
DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", PROB_VERY_LIKELY,
|
| 77 |
|
|
PRED_FLAG_FIRST_MATCH)
|
| 78 |
|
|
|
| 79 |
|
|
/* Loopback edge is taken. */
|
| 80 |
|
|
DEF_PREDICTOR (PRED_LOOP_BRANCH, "loop branch", HITRATE (86),
|
| 81 |
|
|
PRED_FLAG_FIRST_MATCH)
|
| 82 |
|
|
|
| 83 |
|
|
/* Edge causing loop to terminate is probably not taken. */
|
| 84 |
|
|
DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (91),
|
| 85 |
|
|
PRED_FLAG_FIRST_MATCH)
|
| 86 |
|
|
|
| 87 |
|
|
/* Pointers are usually not NULL. */
|
| 88 |
|
|
DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (85), 0)
|
| 89 |
|
|
DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (85), 0)
|
| 90 |
|
|
|
| 91 |
|
|
/* NE is probable, EQ not etc... */
|
| 92 |
|
|
DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (79), 0)
|
| 93 |
|
|
DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (71), 0)
|
| 94 |
|
|
DEF_PREDICTOR (PRED_FPOPCODE, "fp_opcode", HITRATE (90), 0)
|
| 95 |
|
|
DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)", HITRATE (73), 0)
|
| 96 |
|
|
DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", HITRATE (72), 0)
|
| 97 |
|
|
DEF_PREDICTOR (PRED_TREE_FPOPCODE, "fp_opcode (on trees)", HITRATE (90), 0)
|
| 98 |
|
|
|
| 99 |
|
|
/* Branch guarding call is probably taken. */
|
| 100 |
|
|
DEF_PREDICTOR (PRED_CALL, "call", HITRATE (71), 0)
|
| 101 |
|
|
|
| 102 |
|
|
/* Branch causing function to terminate is probably not taken. */
|
| 103 |
|
|
DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (61), 0)
|
| 104 |
|
|
|
| 105 |
|
|
/* Branch containing goto is probably not taken. */
|
| 106 |
|
|
DEF_PREDICTOR (PRED_GOTO, "goto", HITRATE (70), 0)
|
| 107 |
|
|
|
| 108 |
|
|
/* Branch ending with return constant is probably not taken. */
|
| 109 |
|
|
DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (67), 0)
|
| 110 |
|
|
|
| 111 |
|
|
/* Branch ending with return negative constant is probably not taken. */
|
| 112 |
|
|
DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (96), 0)
|
| 113 |
|
|
|
| 114 |
|
|
/* Branch ending with return; is probably not taken */
|
| 115 |
|
|
DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (90), 0)
|
| 116 |
|
|
|
| 117 |
|
|
/* Branches to a mudflap bounds check are extremely unlikely. */
|
| 118 |
|
|
DEF_PREDICTOR (PRED_MUDFLAP, "mudflap check", PROB_VERY_LIKELY, 0)
|
