119 lines
4.9 KiB
Modula-2
119 lines
4.9 KiB
Modula-2
/* Definitions for the branch prediction routines in the GNU compiler.
|
|
Copyright (C) 2001, 2003, 2004, 2007 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 (56), 0)
|
|
|
|
/* Branch to basic block containing call marked by noreturn attribute. */
|
|
DEF_PREDICTOR (PRED_NORETURN, "noreturn call", HITRATE (99),
|
|
PRED_FLAG_FIRST_MATCH)
|
|
|
|
/* Branch to basic block containing call marked by cold function attribute. */
|
|
DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", HITRATE (99),
|
|
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 (70), 0)
|
|
DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", HITRATE (69), 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 (69), 0)
|
|
|
|
/* Branch causing function to terminate is probably not taken. */
|
|
DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (54), 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 (96), 0)
|
|
|
|
/* Branches to a mudflap bounds check are extremely unlikely. */
|
|
DEF_PREDICTOR (PRED_MUDFLAP, "mudflap check", PROB_VERY_LIKELY, 0)
|