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comparison gcc/predict.def @ 131:84e7813d76e9

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gcc-8.2
author mir3636
date Thu, 25 Oct 2018 07:37:49 +0900
parents 04ced10e8804
children 1830386684a0
comparison
equal deleted inserted replaced
111:04ced10e8804 131:84e7813d76e9
1 /* Definitions for the branch prediction routines in the GNU compiler. 1 /* Definitions for the branch prediction routines in the GNU compiler.
2 Copyright (C) 2001-2017 Free Software Foundation, Inc. 2 Copyright (C) 2001-2018 Free Software Foundation, Inc.
3 3
4 This file is part of GCC. 4 This file is part of GCC.
5 5
6 GCC is free software; you can redistribute it and/or modify it under 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 7 the terms of the GNU General Public License as published by the Free
20 /* Before including this file, you should define a macro: 20 /* Before including this file, you should define a macro:
21 21
22 DEF_PREDICTOR (ENUM, NAME, HITRATE) 22 DEF_PREDICTOR (ENUM, NAME, HITRATE)
23 23
24 This macro will be called once for each predictor. The ENUM will 24 This macro will be called once for each predictor. The ENUM will
25 be of type `enum predictor', and will enumerate all supported 25 be of type `enum br_predictor', and will enumerate all supported
26 predictors. The order of DEF_PREDICTOR calls is important, as 26 predictors. The order of DEF_PREDICTOR calls is important, as
27 in the first match combining heuristics, the predictor appearing 27 in the first match combining heuristics, the predictor appearing
28 first in this file will win. 28 first in this file will win.
29 29
30 NAME is used in the debugging output to determine predictor type. 30 NAME is used in the debugging output to determine predictor type.
49 49
50 /* Mark unconditional jump as taken. */ 50 /* Mark unconditional jump as taken. */
51 DEF_PREDICTOR (PRED_UNCONDITIONAL, "unconditional jump", PROB_ALWAYS, 51 DEF_PREDICTOR (PRED_UNCONDITIONAL, "unconditional jump", PROB_ALWAYS,
52 PRED_FLAG_FIRST_MATCH) 52 PRED_FLAG_FIRST_MATCH)
53 53
54 /* Return value of malloc function is almost always non-null. */
55 DEF_PREDICTOR (PRED_MALLOC_NONNULL, "malloc returned non-NULL", \
56 PROB_VERY_LIKELY, PRED_FLAG_FIRST_MATCH)
57
54 /* Use number of loop iterations determined by # of iterations 58 /* Use number of loop iterations determined by # of iterations
55 analysis to set probability. We don't want to use Dempster-Shaffer 59 analysis to set probability. We don't want to use Dempster-Shaffer
56 theory here, as the predictions is exact. */ 60 theory here, as the predictions is exact. */
57 DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_ALWAYS, 61 DEF_PREDICTOR (PRED_LOOP_ITERATIONS, "loop iterations", PROB_UNINITIALIZED,
58 PRED_FLAG_FIRST_MATCH) 62 PRED_FLAG_FIRST_MATCH)
59 63
60 /* Assume that any given atomic operation has low contention, 64 /* Assume that any given atomic operation has low contention,
61 and thus the compare-and-swap operation succeeds. */ 65 and thus the compare-and-swap operation succeeds. */
62 DEF_PREDICTOR (PRED_COMPARE_AND_SWAP, "compare and swap", PROB_VERY_LIKELY, 66 DEF_PREDICTOR (PRED_COMPARE_AND_SWAP, "compare and swap", PROB_VERY_LIKELY,
67 builtin_expect_probability with a default value of HITRATE(90). 71 builtin_expect_probability with a default value of HITRATE(90).
68 Refer to param.def for details. */ 72 Refer to param.def for details. */
69 DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY, 73 DEF_PREDICTOR (PRED_BUILTIN_EXPECT, "__builtin_expect", PROB_VERY_LIKELY,
70 PRED_FLAG_FIRST_MATCH) 74 PRED_FLAG_FIRST_MATCH)
71 75
76 /* Hints provided by user via __builtin_expect_with_probability. */
77 DEF_PREDICTOR (PRED_BUILTIN_EXPECT_WITH_PROBABILITY,
78 "__builtin_expect_with_probability", PROB_UNINITIALIZED,
79 PRED_FLAG_FIRST_MATCH)
80
72 /* Use number of loop iterations guessed by the contents of the loop. */ 81 /* Use number of loop iterations guessed by the contents of the loop. */
73 DEF_PREDICTOR (PRED_LOOP_ITERATIONS_GUESSED, "guessed loop iterations", 82 DEF_PREDICTOR (PRED_LOOP_ITERATIONS_GUESSED, "guessed loop iterations",
74 PROB_ALWAYS, PRED_FLAG_FIRST_MATCH) 83 PROB_UNINITIALIZED, PRED_FLAG_FIRST_MATCH)
75 84
76 /* Use number of loop iterations guessed by the contents of the loop. */ 85 /* Use number of loop iterations guessed by the contents of the loop. */
77 DEF_PREDICTOR (PRED_LOOP_ITERATIONS_MAX, "guessed loop iterations", 86 DEF_PREDICTOR (PRED_LOOP_ITERATIONS_MAX, "guessed loop iterations",
78 PROB_ALWAYS, PRED_FLAG_FIRST_MATCH) 87 PROB_UNINITIALIZED, PRED_FLAG_FIRST_MATCH)
79 88
80 /* Branch containing goto is probably not taken. */ 89 /* Branch containing goto is probably not taken. */
81 DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (67), 0) 90 DEF_PREDICTOR (PRED_CONTINUE, "continue", HITRATE (67), 0)
82 91
83 /* Branch to basic block containing call marked by noreturn attribute. */ 92 /* Branch to basic block containing call marked by noreturn attribute. */
87 /* Branch to basic block containing call marked by cold function attribute. */ 96 /* Branch to basic block containing call marked by cold function attribute. */
88 DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", PROB_VERY_LIKELY, 97 DEF_PREDICTOR (PRED_COLD_FUNCTION, "cold function call", PROB_VERY_LIKELY,
89 PRED_FLAG_FIRST_MATCH) 98 PRED_FLAG_FIRST_MATCH)
90 99
91 /* Edge causing loop to terminate is probably not taken. */ 100 /* Edge causing loop to terminate is probably not taken. */
92 DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (85), 101 DEF_PREDICTOR (PRED_LOOP_EXIT, "loop exit", HITRATE (89),
93 PRED_FLAG_FIRST_MATCH) 102 PRED_FLAG_FIRST_MATCH)
94 103
95 /* Same as LOOP_EXIT but for loops containing recursive call. */ 104 /* Same as LOOP_EXIT but for loops containing recursive call. */
96 DEF_PREDICTOR (PRED_LOOP_EXIT_WITH_RECURSION, "loop exit with recursion", 105 DEF_PREDICTOR (PRED_LOOP_EXIT_WITH_RECURSION, "loop exit with recursion",
97 HITRATE (72), PRED_FLAG_FIRST_MATCH) 106 HITRATE (78), PRED_FLAG_FIRST_MATCH)
98 107
99 /* Edge causing loop to terminate by computing value used by later 108 /* Edge causing loop to terminate by computing value used by later
100 conditional. */ 109 conditional. */
101 DEF_PREDICTOR (PRED_LOOP_EXTRA_EXIT, "extra loop exit", HITRATE (83), 110 DEF_PREDICTOR (PRED_LOOP_EXTRA_EXIT, "extra loop exit", HITRATE (67),
102 PRED_FLAG_FIRST_MATCH) 111 PRED_FLAG_FIRST_MATCH)
103 112
104 /* Pointers are usually not NULL. */ 113 /* Pointers are usually not NULL. */
105 DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (70), 0) 114 DEF_PREDICTOR (PRED_POINTER, "pointer", HITRATE (70), 0)
106 DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (70), 0) 115 DEF_PREDICTOR (PRED_TREE_POINTER, "pointer (on trees)", HITRATE (70), 0)
107 116
108 /* NE is probable, EQ not etc... */ 117 /* NE is probable, EQ not etc... */
109 DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (64), 0) 118 DEF_PREDICTOR (PRED_OPCODE_POSITIVE, "opcode values positive", HITRATE (59), 0)
110 DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (66), 0) 119 DEF_PREDICTOR (PRED_OPCODE_NONEQUAL, "opcode values nonequal", HITRATE (66), 0)
111 DEF_PREDICTOR (PRED_FPOPCODE, "fp_opcode", HITRATE (90), 0) 120 DEF_PREDICTOR (PRED_FPOPCODE, "fp_opcode", HITRATE (90), 0)
112 DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)", 121 DEF_PREDICTOR (PRED_TREE_OPCODE_POSITIVE, "opcode values positive (on trees)",
113 HITRATE (64), 0) 122 HITRATE (59), 0)
114 DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)", 123 DEF_PREDICTOR (PRED_TREE_OPCODE_NONEQUAL, "opcode values nonequal (on trees)",
115 HITRATE (66), 0) 124 HITRATE (66), 0)
116 DEF_PREDICTOR (PRED_TREE_FPOPCODE, "fp_opcode (on trees)", HITRATE (90), 0) 125 DEF_PREDICTOR (PRED_TREE_FPOPCODE, "fp_opcode (on trees)", HITRATE (90), 0)
117 126
118 /* Branch guarding call is probably taken. */ 127 /* Branch guarding call is probably taken. */
119 DEF_PREDICTOR (PRED_CALL, "call", HITRATE (67), 0) 128 DEF_PREDICTOR (PRED_CALL, "call", HITRATE (67), 0)
120 129
121 /* PRED_CALL is not very reliable predictor and it turns out to be even 130 /* Call predictors are for now ignored, lets leave the predictor
122 less reliable for indirect calls and polymorphic calls. For spec2k6 131 to measure its benefit. */
123 the predictio nis slightly in the direction of taking the call. */ 132 DEF_PREDICTOR (PRED_INDIR_CALL, "indirect call", PROB_EVEN, 0)
124 DEF_PREDICTOR (PRED_INDIR_CALL, "indirect call", HITRATE (86), 0) 133 DEF_PREDICTOR (PRED_POLYMORPHIC_CALL, "polymorphic call", PROB_EVEN, 0)
125 DEF_PREDICTOR (PRED_POLYMORPHIC_CALL, "polymorphic call", HITRATE (59), 0) 134 DEF_PREDICTOR (PRED_RECURSIVE_CALL, "recursive call", PROB_EVEN, 0)
126
127 /* Recursive calls are usually not taken or the function will recurse
128 indefinitely. */
129 DEF_PREDICTOR (PRED_RECURSIVE_CALL, "recursive call", HITRATE (75), 0)
130 135
131 /* Branch causing function to terminate is probably not taken. */ 136 /* Branch causing function to terminate is probably not taken. */
132 DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (66), 137 DEF_PREDICTOR (PRED_TREE_EARLY_RETURN, "early return (on trees)", HITRATE (66),
133 0) 138 0)
134 139
135 /* Branch containing goto is probably not taken. */ 140 /* Branch containing goto is probably not taken. */
136 DEF_PREDICTOR (PRED_GOTO, "goto", HITRATE (66), 0) 141 DEF_PREDICTOR (PRED_GOTO, "goto", HITRATE (66), 0)
137 142
138 /* Branch ending with return constant is probably not taken. */ 143 /* Branch ending with return constant is probably not taken. */
139 DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (69), 0) 144 DEF_PREDICTOR (PRED_CONST_RETURN, "const return", HITRATE (65), 0)
140 145
141 /* Branch ending with return negative constant is probably not taken. */ 146 /* Branch ending with return negative constant is probably not taken. */
142 DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (98), 0) 147 DEF_PREDICTOR (PRED_NEGATIVE_RETURN, "negative return", HITRATE (98), 0)
143 148
144 /* Branch ending with return; is probably not taken */ 149 /* Branch ending with return; is probably not taken */
145 DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (91), 0) 150 DEF_PREDICTOR (PRED_NULL_RETURN, "null return", HITRATE (71), 0)
146 151
147 /* Branches to compare induction variable to a loop bound is 152 /* Branches to compare induction variable to a loop bound is
148 extremely likely. */ 153 extremely likely. */
149 DEF_PREDICTOR (PRED_LOOP_IV_COMPARE_GUESS, "guess loop iv compare", 154 DEF_PREDICTOR (PRED_LOOP_IV_COMPARE_GUESS, "guess loop iv compare",
150 HITRATE (98), 0) 155 HITRATE (64), 0)
151 156
152 /* Use number of loop iterations determined by # of iterations analysis 157 /* Use number of loop iterations determined by # of iterations analysis
153 to set probability of branches that compares IV to loop bound variable. */ 158 to set probability of branches that compares IV to loop bound variable. */
154 DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_VERY_LIKELY, 159 DEF_PREDICTOR (PRED_LOOP_IV_COMPARE, "loop iv compare", PROB_UNINITIALIZED,
155 PRED_FLAG_FIRST_MATCH) 160 PRED_FLAG_FIRST_MATCH)
156 161
157 /* In the following code 162 /* In the following code
158 for (loop1) 163 for (loop1)
159 if (cond) 164 if (cond)
160 for (loop2) 165 for (loop2)
161 body; 166 body;
162 guess that cond is unlikely. */ 167 guess that cond is unlikely. */
163 DEF_PREDICTOR (PRED_LOOP_GUARD, "loop guard", HITRATE (66), 0) 168 DEF_PREDICTOR (PRED_LOOP_GUARD, "loop guard", HITRATE (73), 0)
164 169
165 /* Same but for loops containing recursion. */ 170 /* Same but for loops containing recursion. */
166 DEF_PREDICTOR (PRED_LOOP_GUARD_WITH_RECURSION, "loop guard with recursion", 171 DEF_PREDICTOR (PRED_LOOP_GUARD_WITH_RECURSION, "loop guard with recursion",
167 HITRATE (85), 0) 172 HITRATE (85), 0)
168 173
170 DEF_PREDICTOR (PRED_HOT_LABEL, "hot label", HITRATE (85), 0) 175 DEF_PREDICTOR (PRED_HOT_LABEL, "hot label", HITRATE (85), 0)
171 176
172 /* Branches to cold labels are extremely unlikely. */ 177 /* Branches to cold labels are extremely unlikely. */
173 DEF_PREDICTOR (PRED_COLD_LABEL, "cold label", PROB_VERY_LIKELY, 178 DEF_PREDICTOR (PRED_COLD_LABEL, "cold label", PROB_VERY_LIKELY,
174 PRED_FLAG_FIRST_MATCH) 179 PRED_FLAG_FIRST_MATCH)
175
176 180
177 /* The following predictors are used in Fortran. */ 181 /* The following predictors are used in Fortran. */
178 182
179 /* Branch leading to an integer overflow are extremely unlikely. */ 183 /* Branch leading to an integer overflow are extremely unlikely. */
180 DEF_PREDICTOR (PRED_FORTRAN_OVERFLOW, "Fortran overflow", PROB_ALWAYS, 184 DEF_PREDICTOR (PRED_FORTRAN_OVERFLOW, "Fortran overflow", PROB_ALWAYS,