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1 | #!/usr/bin/env python3 |
2 | # | |
3 | # Script to analyze results of our branch prediction heuristics | |
4 | # | |
5 | # This file is part of GCC. | |
6 | # | |
7 | # GCC is free software; you can redistribute it and/or modify it under | |
8 | # the terms of the GNU General Public License as published by the Free | |
9 | # Software Foundation; either version 3, or (at your option) any later | |
10 | # version. | |
11 | # | |
12 | # GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | # WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | # FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | # for more details. | |
16 | # | |
17 | # You should have received a copy of the GNU General Public License | |
18 | # along with GCC; see the file COPYING3. If not see | |
19 | # <http://www.gnu.org/licenses/>. */ | |
20 | # | |
21 | # | |
22 | # | |
23 | # This script is used to calculate two basic properties of the branch prediction | |
24 | # heuristics - coverage and hitrate. Coverage is number of executions | |
25 | # of a given branch matched by the heuristics and hitrate is probability | |
26 | # that once branch is predicted as taken it is really taken. | |
27 | # | |
28 | # These values are useful to determine the quality of given heuristics. | |
29 | # Hitrate may be directly used in predict.def. | |
30 | # | |
31 | # Usage: | |
32 | # Step 1: Compile and profile your program. You need to use -fprofile-generate | |
33 | # flag to get the profiles. | |
34 | # Step 2: Make a reference run of the intrumented application. | |
35 | # Step 3: Compile the program with collected profile and dump IPA profiles | |
36 | # (-fprofile-use -fdump-ipa-profile-details) | |
37 | # Step 4: Collect all generated dump files: | |
38 | # find . -name '*.profile' | xargs cat > dump_file | |
39 | # Step 5: Run the script: | |
40 | # ./analyze_brprob.py dump_file | |
41 | # and read results. Basically the following table is printed: | |
42 | # | |
43 | # HEURISTICS BRANCHES (REL) HITRATE COVERAGE (REL) | |
44 | # early return (on trees) 3 0.2% 35.83% / 93.64% 66360 0.0% | |
45 | # guess loop iv compare 8 0.6% 53.35% / 53.73% 11183344 0.0% | |
46 | # call 18 1.4% 31.95% / 69.95% 51880179 0.2% | |
47 | # loop guard 23 1.8% 84.13% / 84.85% 13749065956 42.2% | |
48 | # opcode values positive (on trees) 42 3.3% 15.71% / 84.81% 6771097902 20.8% | |
49 | # opcode values nonequal (on trees) 226 17.6% 72.48% / 72.84% 844753864 2.6% | |
50 | # loop exit 231 18.0% 86.97% / 86.98% 8952666897 27.5% | |
51 | # loop iterations 239 18.6% 91.10% / 91.10% 3062707264 9.4% | |
52 | # DS theory 281 21.9% 82.08% / 83.39% 7787264075 23.9% | |
53 | # no prediction 293 22.9% 46.92% / 70.70% 2293267840 7.0% | |
54 | # guessed loop iterations 313 24.4% 76.41% / 76.41% 10782750177 33.1% | |
55 | # first match 708 55.2% 82.30% / 82.31% 22489588691 69.0% | |
56 | # combined 1282 100.0% 79.76% / 81.75% 32570120606 100.0% | |
57 | # | |
58 | # | |
59 | # The heuristics called "first match" is a heuristics used by GCC branch | |
60 | # prediction pass and it predicts 55.2% branches correctly. As you can, | |
61 | # the heuristics has very good covertage (69.05%). On the other hand, | |
62 | # "opcode values nonequal (on trees)" heuristics has good hirate, but poor | |
63 | # coverage. | |
64 | ||
65 | import sys | |
66 | import os | |
67 | import re | |
0d73e480 | 68 | import argparse |
4877829b ML |
69 | |
70 | def percentage(a, b): | |
71 | return 100.0 * a / b | |
72 | ||
73 | class Summary: | |
74 | def __init__(self, name): | |
75 | self.name = name | |
76 | self.branches = 0 | |
77 | self.count = 0 | |
78 | self.hits = 0 | |
79 | self.fits = 0 | |
80 | ||
0d73e480 ML |
81 | def get_hitrate(self): |
82 | return self.hits / self.count | |
83 | ||
4877829b ML |
84 | def count_formatted(self): |
85 | v = self.count | |
86 | for unit in ['','K','M','G','T','P','E','Z']: | |
87 | if v < 1000: | |
88 | return "%3.2f%s" % (v, unit) | |
89 | v /= 1000.0 | |
90 | return "%.1f%s" % (v, 'Y') | |
91 | ||
92 | class Profile: | |
93 | def __init__(self, filename): | |
94 | self.filename = filename | |
95 | self.heuristics = {} | |
96 | ||
97 | def add(self, name, prediction, count, hits): | |
98 | if not name in self.heuristics: | |
99 | self.heuristics[name] = Summary(name) | |
100 | ||
101 | s = self.heuristics[name] | |
102 | s.branches += 1 | |
103 | s.count += count | |
104 | if prediction < 50: | |
105 | hits = count - hits | |
106 | s.hits += hits | |
107 | s.fits += max(hits, count - hits) | |
108 | ||
109 | def branches_max(self): | |
110 | return max([v.branches for k, v in self.heuristics.items()]) | |
111 | ||
112 | def count_max(self): | |
113 | return max([v.count for k, v in self.heuristics.items()]) | |
114 | ||
0d73e480 ML |
115 | def dump(self, sorting): |
116 | sorter = lambda x: x[1].branches | |
117 | if sorting == 'hitrate': | |
118 | sorter = lambda x: x[1].get_hitrate() | |
119 | elif sorting == 'coverage': | |
120 | sorter = lambda x: x[1].count | |
121 | ||
4877829b ML |
122 | print('%-36s %8s %6s %-16s %14s %8s %6s' % ('HEURISTICS', 'BRANCHES', '(REL)', |
123 | 'HITRATE', 'COVERAGE', 'COVERAGE', '(REL)')) | |
0d73e480 | 124 | for (k, v) in sorted(self.heuristics.items(), key = sorter): |
4877829b ML |
125 | print('%-36s %8i %5.1f%% %6.2f%% / %6.2f%% %14i %8s %5.1f%%' % |
126 | (k, v.branches, percentage(v.branches, self.branches_max ()), | |
127 | percentage(v.hits, v.count), percentage(v.fits, v.count), | |
128 | v.count, v.count_formatted(), percentage(v.count, self.count_max()) )) | |
129 | ||
0d73e480 ML |
130 | parser = argparse.ArgumentParser() |
131 | parser.add_argument('dump_file', metavar = 'dump_file', help = 'IPA profile dump file') | |
132 | parser.add_argument('-s', '--sorting', dest = 'sorting', choices = ['branches', 'hitrate', 'coverage'], default = 'branches') | |
133 | ||
134 | args = parser.parse_args() | |
4877829b ML |
135 | |
136 | profile = Profile(sys.argv[1]) | |
e49efc14 | 137 | r = re.compile(' (.*) heuristics( of edge [0-9]*->[0-9]*)?( \\(.*\\))?: (.*)%.*exec ([0-9]*) hit ([0-9]*)') |
0d73e480 | 138 | for l in open(args.dump_file).readlines(): |
4877829b | 139 | m = r.match(l) |
e49efc14 | 140 | if m != None and m.group(3) == None: |
4877829b | 141 | name = m.group(1) |
e49efc14 ML |
142 | prediction = float(m.group(4)) |
143 | count = int(m.group(5)) | |
144 | hits = int(m.group(6)) | |
4877829b ML |
145 | |
146 | profile.add(name, prediction, count, hits) | |
147 | ||
0d73e480 | 148 | profile.dump(args.sorting) |