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448fda2b 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
65import sys
66import os
67import re
2a364b38 68import argparse
448fda2b 69
fbf561f4 70from math import *
71
899669a3 72counter_aggregates = set(['combined', 'first match', 'DS theory',
73 'no prediction'])
041d9b52 74hot_threshold = 10
899669a3 75
448fda2b 76def percentage(a, b):
77 return 100.0 * a / b
78
fbf561f4 79def average(values):
80 return 1.0 * sum(values) / len(values)
81
82def average_cutoff(values, cut):
83 l = len(values)
84 skip = floor(l * cut / 2)
85 if skip > 0:
86 values.sort()
87 values = values[skip:-skip]
88 return average(values)
89
90def median(values):
91 values.sort()
92 return values[int(len(values) / 2)]
93
c3c9b6da 94class PredictDefFile:
95 def __init__(self, path):
96 self.path = path
97 self.predictors = {}
98
99 def parse_and_modify(self, heuristics, write_def_file):
100 lines = [x.rstrip() for x in open(self.path).readlines()]
101
102 p = None
103 modified_lines = []
104 for l in lines:
105 if l.startswith('DEF_PREDICTOR'):
106 m = re.match('.*"(.*)".*', l)
107 p = m.group(1)
108 elif l == '':
109 p = None
110
111 if p != None:
112 heuristic = [x for x in heuristics if x.name == p]
113 heuristic = heuristic[0] if len(heuristic) == 1 else None
114
115 m = re.match('.*HITRATE \(([^)]*)\).*', l)
116 if (m != None):
117 self.predictors[p] = int(m.group(1))
118
119 # modify the line
120 if heuristic != None:
121 new_line = (l[:m.start(1)]
122 + str(round(heuristic.get_hitrate()))
123 + l[m.end(1):])
124 l = new_line
125 p = None
126 elif 'PROB_VERY_LIKELY' in l:
127 self.predictors[p] = 100
128 modified_lines.append(l)
129
130 # save the file
131 if write_def_file:
132 with open(self.path, 'w+') as f:
133 for l in modified_lines:
134 f.write(l + '\n')
041d9b52 135class Heuristics:
136 def __init__(self, count, hits, fits):
137 self.count = count
138 self.hits = hits
139 self.fits = fits
c3c9b6da 140
448fda2b 141class Summary:
142 def __init__(self, name):
143 self.name = name
041d9b52 144 self.edges= []
145
146 def branches(self):
147 return len(self.edges)
148
149 def hits(self):
150 return sum([x.hits for x in self.edges])
151
152 def fits(self):
153 return sum([x.fits for x in self.edges])
154
155 def count(self):
156 return sum([x.count for x in self.edges])
157
158 def successfull_branches(self):
159 return len([x for x in self.edges if 2 * x.hits >= x.count])
448fda2b 160
2a364b38 161 def get_hitrate(self):
041d9b52 162 return 100.0 * self.hits() / self.count()
899669a3 163
164 def get_branch_hitrate(self):
041d9b52 165 return 100.0 * self.successfull_branches() / self.branches()
2a364b38 166
448fda2b 167 def count_formatted(self):
041d9b52 168 v = self.count()
b705676e 169 for unit in ['', 'k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y']:
448fda2b 170 if v < 1000:
171 return "%3.2f%s" % (v, unit)
172 v /= 1000.0
173 return "%.1f%s" % (v, 'Y')
174
041d9b52 175 def count(self):
176 return sum([x.count for x in self.edges])
177
c3c9b6da 178 def print(self, branches_max, count_max, predict_def):
041d9b52 179 # filter out most hot edges (if requested)
180 self.edges = sorted(self.edges, reverse = True, key = lambda x: x.count)
181 if args.coverage_threshold != None:
182 threshold = args.coverage_threshold * self.count() / 100
183 edges = [x for x in self.edges if x.count < threshold]
184 if len(edges) != 0:
185 self.edges = edges
186
c3c9b6da 187 predicted_as = None
188 if predict_def != None and self.name in predict_def.predictors:
189 predicted_as = predict_def.predictors[self.name]
190
899669a3 191 print('%-40s %8i %5.1f%% %11.2f%% %7.2f%% / %6.2f%% %14i %8s %5.1f%%' %
041d9b52 192 (self.name, self.branches(),
193 percentage(self.branches(), branches_max),
899669a3 194 self.get_branch_hitrate(),
195 self.get_hitrate(),
041d9b52 196 percentage(self.fits(), self.count()),
197 self.count(), self.count_formatted(),
198 percentage(self.count(), count_max)), end = '')
c3c9b6da 199
200 if predicted_as != None:
201 print('%12i%% %5.1f%%' % (predicted_as,
202 self.get_hitrate() - predicted_as), end = '')
041d9b52 203 else:
204 print(' ' * 20, end = '')
205
206 # print details about the most important edges
207 if args.coverage_threshold == None:
208 edges = [x for x in self.edges[:100] if x.count * hot_threshold > self.count()]
209 if args.verbose:
210 for c in edges:
211 r = 100.0 * c.count / self.count()
212 print(' %.0f%%:%d' % (r, c.count), end = '')
213 elif len(edges) > 0:
214 print(' %0.0f%%:%d' % (100.0 * sum([x.count for x in edges]) / self.count(), len(edges)), end = '')
215
c3c9b6da 216 print()
899669a3 217
448fda2b 218class Profile:
219 def __init__(self, filename):
220 self.filename = filename
221 self.heuristics = {}
fbf561f4 222 self.niter_vector = []
448fda2b 223
224 def add(self, name, prediction, count, hits):
225 if not name in self.heuristics:
226 self.heuristics[name] = Summary(name)
227
228 s = self.heuristics[name]
899669a3 229
448fda2b 230 if prediction < 50:
231 hits = count - hits
899669a3 232 remaining = count - hits
041d9b52 233 fits = max(hits, remaining)
899669a3 234
041d9b52 235 s.edges.append(Heuristics(count, hits, fits))
448fda2b 236
fbf561f4 237 def add_loop_niter(self, niter):
238 if niter > 0:
239 self.niter_vector.append(niter)
240
448fda2b 241 def branches_max(self):
041d9b52 242 return max([v.branches() for k, v in self.heuristics.items()])
448fda2b 243
244 def count_max(self):
041d9b52 245 return max([v.count() for k, v in self.heuristics.items()])
448fda2b 246
c3c9b6da 247 def print_group(self, sorting, group_name, heuristics, predict_def):
899669a3 248 count_max = self.count_max()
249 branches_max = self.branches_max()
250
041d9b52 251 sorter = lambda x: x.branches()
899669a3 252 if sorting == 'branch-hitrate':
253 sorter = lambda x: x.get_branch_hitrate()
254 elif sorting == 'hitrate':
255 sorter = lambda x: x.get_hitrate()
2a364b38 256 elif sorting == 'coverage':
899669a3 257 sorter = lambda x: x.count
258 elif sorting == 'name':
259 sorter = lambda x: x.name.lower()
260
041d9b52 261 print('%-40s %8s %6s %12s %18s %14s %8s %6s %12s %6s %s' %
899669a3 262 ('HEURISTICS', 'BRANCHES', '(REL)',
c3c9b6da 263 'BR. HITRATE', 'HITRATE', 'COVERAGE', 'COVERAGE', '(REL)',
041d9b52 264 'predict.def', '(REL)', 'HOT branches (>%d%%)' % hot_threshold))
899669a3 265 for h in sorted(heuristics, key = sorter):
c3c9b6da 266 h.print(branches_max, count_max, predict_def)
899669a3 267
268 def dump(self, sorting):
269 heuristics = self.heuristics.values()
270 if len(heuristics) == 0:
271 print('No heuristics available')
272 return
273
c3c9b6da 274 predict_def = None
275 if args.def_file != None:
276 predict_def = PredictDefFile(args.def_file)
277 predict_def.parse_and_modify(heuristics, args.write_def_file)
278
899669a3 279 special = list(filter(lambda x: x.name in counter_aggregates,
280 heuristics))
281 normal = list(filter(lambda x: x.name not in counter_aggregates,
282 heuristics))
2a364b38 283
c3c9b6da 284 self.print_group(sorting, 'HEURISTICS', normal, predict_def)
899669a3 285 print()
c3c9b6da 286 self.print_group(sorting, 'HEURISTIC AGGREGATES', special, predict_def)
448fda2b 287
f849b304 288 if len(self.niter_vector) > 0:
289 print ('\nLoop count: %d' % len(self.niter_vector)),
290 print(' avg. # of iter: %.2f' % average(self.niter_vector))
291 print(' median # of iter: %.2f' % median(self.niter_vector))
292 for v in [1, 5, 10, 20, 30]:
293 cut = 0.01 * v
899669a3 294 print(' avg. (%d%% cutoff) # of iter: %.2f'
295 % (v, average_cutoff(self.niter_vector, cut)))
fbf561f4 296
2a364b38 297parser = argparse.ArgumentParser()
899669a3 298parser.add_argument('dump_file', metavar = 'dump_file',
299 help = 'IPA profile dump file')
300parser.add_argument('-s', '--sorting', dest = 'sorting',
301 choices = ['branches', 'branch-hitrate', 'hitrate', 'coverage', 'name'],
302 default = 'branches')
c3c9b6da 303parser.add_argument('-d', '--def-file', help = 'path to predict.def')
304parser.add_argument('-w', '--write-def-file', action = 'store_true',
305 help = 'Modify predict.def file in order to set new numbers')
041d9b52 306parser.add_argument('-c', '--coverage-threshold', type = int,
307 help = 'Ignore edges that have percentage coverage >= coverage-threshold')
308parser.add_argument('-v', '--verbose', action = 'store_true', help = 'Print verbose informations')
2a364b38 309
310args = parser.parse_args()
448fda2b 311
c3c9b6da 312profile = Profile(args.dump_file)
fbf561f4 313loop_niter_str = ';; profile-based iteration count: '
041d9b52 314
c3c9b6da 315for l in open(args.dump_file):
041d9b52 316 if l.startswith(';;heuristics;'):
317 parts = l.strip().split(';')
318 assert len(parts) == 8
319 name = parts[3]
320 prediction = float(parts[6])
321 count = int(parts[4])
322 hits = int(parts[5])
448fda2b 323
324 profile.add(name, prediction, count, hits)
fbf561f4 325 elif l.startswith(loop_niter_str):
326 v = int(l[len(loop_niter_str):])
327 profile.add_loop_niter(v)
448fda2b 328
2a364b38 329profile.dump(args.sorting)