source: arduino-1-6-7/trunk/fuentes/arduino-ide-amd64/hardware/tools/avr/lib/gcc/avr/4.9.2/plugin/include/predict.def @ 4837

Last change on this file since 4837 was 4837, checked in by daduve, 2 years ago

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1/* Definitions for the branch prediction routines in the GNU compiler.
2   Copyright (C) 2001-2014 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING3.  If not see
18<http://www.gnu.org/licenses/>.  */
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.  */
38DEF_PREDICTOR (PRED_COMBINED, "combined", PROB_ALWAYS, 0)
39
40/* An outcome estimated by Dempster-Shaffer theory.  */
41DEF_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.  */
45DEF_PREDICTOR (PRED_FIRST_MATCH, "first match", PROB_ALWAYS, 0)
46
47/* Heuristic applying when no heuristic below applies.  */
48DEF_PREDICTOR (PRED_NO_PREDICTION, "no prediction", PROB_ALWAYS, 0)
49
50/* Mark unconditional jump as taken.  */
51DEF_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.  */
57DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS,
58               PRED_FLAG_FIRST_MATCH)
59
60/* Assume that any given atomic operation has low contention,
61   and thus the compare-and-swap operation succeeds. */
62DEF_PREDICTOR (PRED_COMPARE_AND_SWAP, "compare and swap", PROB_VERY_LIKELY,
63               PRED_FLAG_FIRST_MATCH)
64
65/* Hints dropped by user via __builtin_expect feature.  Note: the
66   probability of PROB_VERY_LIKELY is now overwritten by param
67   builtin_expect_probability with a default value of HITRATE(90).
68   Refer to param.def for details.  */
69DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY,
70               PRED_FLAG_FIRST_MATCH)
71
72/* Use number of loop iterations guessed by the contents of the loop.  */
73DEF_PREDICTOR (PRED_LOOP_ITERATIONS_GUESSED, "guessed loop iterations",
74               PROB_ALWAYS, PRED_FLAG_FIRST_MATCH)
75
76/* Branch containing goto is probably not taken.  */
77DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (50), 0)
78
79/* Branch to basic block containing call marked by noreturn attribute.  */
80DEF_PREDICTOR (PRED_NORETURN, "noreturn call", PROB_VERY_LIKELY,
81               PRED_FLAG_FIRST_MATCH)
82
83/* Branch to basic block containing call marked by cold function attribute.  */
84DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", PROB_VERY_LIKELY,
85               PRED_FLAG_FIRST_MATCH)
86
87/* Loopback edge is taken.  */
88DEF_PREDICTOR (PRED_LOOP_BRANCH, "loop branch", HITRATE (86),
89               PRED_FLAG_FIRST_MATCH)
90
91/* Edge causing loop to terminate is probably not taken.  */
92DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (91),
93               PRED_FLAG_FIRST_MATCH)
94
95/* Pointers are usually not NULL.  */
96DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (85), 0)
97DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (85), 0)
98
99/* NE is probable, EQ not etc...  */
100DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (79), 0)
101DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (71), 0)
102DEF_PREDICTOR (PRED_FPOPCODE, "fp_opcode", HITRATE (90), 0)
103DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)", HITRATE (73), 0)
104DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", HITRATE (72), 0)
105DEF_PREDICTOR (PRED_TREE_FPOPCODE, "fp_opcode (on trees)", HITRATE (90), 0)
106
107/* Branch guarding call is probably taken.  */
108DEF_PREDICTOR (PRED_CALL, "call", HITRATE (71), 0)
109
110/* Branch causing function to terminate is probably not taken.  */
111DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (61), 0)
112
113/* Branch containing goto is probably not taken.  */
114DEF_PREDICTOR (PRED_GOTO, "goto", HITRATE (70), 0)
115
116/* Branch ending with return constant is probably not taken.  */
117DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (67), 0)
118
119/* Branch ending with return negative constant is probably not taken.  */
120DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (96), 0)
121
122/* Branch ending with return; is probably not taken */
123DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (90), 0)
124
125/* Branches to compare induction variable to a loop bound is
126   extremely likely.  */
127DEF_PREDICTOR (PRED_LOOP_IV_COMPARE_GUESS, "guess loop iv compare",
128               PROB_VERY_LIKELY, 0)
129
130/* Use number of loop iterations determined by # of iterations analysis
131   to set probability of branches that compares IV to loop bound variable.  */
132DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_VERY_LIKELY,
133               PRED_FLAG_FIRST_MATCH)
134
135/* Branches to hot labels are likely.  */
136DEF_PREDICTOR (PRED_HOT_LABEL, "hot label", HITRATE (85), 0)
137
138/* Branches to cold labels are extremely unlikely.  */
139DEF_PREDICTOR (PRED_COLD_LABEL, "cold label", PROB_VERY_LIKELY,
140               PRED_FLAG_FIRST_MATCH)
141
142
143/* The following predictors are used in Fortran. */
144
145/* Branch leading to an integer overflow are extremely unlikely.  */
146DEF_PREDICTOR (PRED_FORTRAN_OVERFLOW, "overflow", PROB_ALWAYS,
147               PRED_FLAG_FIRST_MATCH)
148
149/* Branch leading to a failure status are unlikely.  This can occur for out
150   of memory or when trying to allocate an already allocated allocated or
151   deallocating an already deallocated allocatable.  This predictor only
152   occurs when the user explicitly asked for a return status.  By default,
153   the code aborts, which is handled via PRED_NORETURN.  */
154DEF_PREDICTOR (PRED_FORTRAN_FAIL_ALLOC, "fail alloc", PROB_VERY_LIKELY, 0)
155
156/* Branch leading to an I/O failure status are unlikely.  This predictor is
157   used for I/O failures such as for invalid unit numbers.  This predictor
158   only occurs when the user explicitly asked for a return status.  By default,
159   the code aborts, which is handled via PRED_NORETURN.  */
160DEF_PREDICTOR (PRED_FORTRAN_FAIL_IO, "fail alloc", HITRATE(85), 0)
161
162/* Branch leading to a run-time warning message which is printed only once
163   are unlikely.  The print-warning branch itself can be likely or unlikely.  */
164DEF_PREDICTOR (PRED_FORTRAN_WARN_ONCE, "warn once", HITRATE (75), 0)
165
166/* Branch belonging to a zero-sized array.  */
167DEF_PREDICTOR (PRED_FORTRAN_SIZE_ZERO, "zero-sized array", HITRATE(70), 0)
168
169/* Branch belonging to an invalid bound index, in a context where it is
170   standard conform and well defined but rather pointless and, hence, rather
171   unlikely to occur.  */
172DEF_PREDICTOR (PRED_FORTRAN_INVALID_BOUND, "zero-sized array", HITRATE(90), 0)
173
174/* Branch belonging to the handling of absent optional arguments.  This
175   predictor is used when an optional dummy argument, associated with an
176   absent argument, is passed on as actual argument to another procedure,
177   which in turn has an optional argument.  */
178DEF_PREDICTOR (PRED_FORTRAN_ABSENT_DUMMY, "absent dummy", HITRATE(60), 0)
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