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17d6c819 | 1 | #!/usr/bin/awk -f |
075cc945 | 2 | # Script to analyze experimental results of our branch prediction heuristics |
f981f97b | 3 | # Contributed by Jan Hubicka, SuSE Inc. |
17d6c819 JH |
4 | # Copyright (C) 2001 Free Software Foundation, Inc. |
5 | # | |
6 | # This file is part of GNU CC. | |
7 | # | |
8 | # GNU CC is free software; you can redistribute it and/or modify | |
9 | # it under the terms of the GNU General Public License as published by | |
10 | # the Free Software Foundation; either version 2, or (at your option) | |
11 | # any later version. | |
12 | # | |
13 | # GNU CC is distributed in the hope that it will be useful, | |
14 | # but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | # GNU General Public License for more details. | |
17 | # | |
18 | # You should have received a copy of the GNU General Public License | |
19 | # along with GNU CC; see the file COPYING. If not, write to | |
20 | # the Free Software Foundation, 59 Temple Place - Suite 330, | |
21 | # Boston, MA 02111-1307, USA. | |
22 | # | |
23 | # | |
24 | # This script is used to calculate two basic properties of the branch prediction | |
a6ed70ef | 25 | # heuristics - coverage and hitrate. Coverage is number of executions of a given |
17d6c819 JH |
26 | # branch matched by the heuristics and hitrate is probability that once branch is |
27 | # predicted as taken it is really taken. | |
28 | # | |
f981f97b | 29 | # These values are useful to determine the quality of given heuristics. Hitrate |
17d6c819 JH |
30 | # may be directly used in predict.c. |
31 | # | |
32 | # Usage: | |
a6ed70ef | 33 | # Step 1: Compile and profile your program. You need to use -fprofile-arcs |
17d6c819 | 34 | # flag to get the profiles |
f981f97b AJ |
35 | # Step 2: Generate log files. The information about given heuristics are |
36 | # saved into *.life dumps. You need to pass the -df switch to the compiler as well | |
37 | # as -fbranch-probabilities to get the results of profiling noted in the dumps. | |
38 | # Ensure that there are no "Arc profiling: some edge counts were bad." warnings. | |
f981f97b | 39 | # Step 3: Run this script to concatenate all *.life files: |
17d6c819 JH |
40 | # analyze_brprob `find . -name *.life` |
41 | # the information is collected and print once all files are parsed. This | |
42 | # may take a while. | |
f981f97b AJ |
43 | # Note that the script does use bc to perform long arithmetic. |
44 | # Step 4: Read the results. Basically the following table is printed: | |
45 | # (this is just an example from a very early stage of branch prediction pass | |
17d6c819 JH |
46 | # development, so please don't take these numbers seriously) |
47 | # | |
48 | #HEURISTICS BRANCHES (REL) HITRATE COVERAGE (REL) | |
49 | #opcode 2889 83.7% 94.96%/ 97.62% 7516383 75.3% | |
50 | #pointer 246 7.1% 99.69%/ 99.86% 118791 1.2% | |
51 | #loop header 449 13.0% 98.32%/ 99.07% 43553 0.4% | |
52 | #first match 3450 100.0% 89.92%/ 97.27% 9979782 100.0% | |
53 | #loop exit 924 26.8% 88.95%/ 95.58% 9026266 90.4% | |
54 | #error return 150 4.3% 64.48%/ 86.81% 453542 4.5% | |
55 | #call 803 23.3% 51.66%/ 98.61% 3614037 36.2% | |
56 | #loop branch 51 1.5% 99.26%/ 99.27% 26854 0.3% | |
57 | #noreturn call 951 27.6% 100.00%/100.00% 1759809 17.6% | |
58 | # | |
f981f97b | 59 | # The heuristic called "first match" is a heuristic used by GCC branch |
075cc945 | 60 | # prediction pass and it predicts 89.92% branches correctly. |
17d6c819 JH |
61 | # |
62 | # The quality of heuristics can be rated using both, coverage and hitrate | |
63 | # parameters. For example "loop branch" heuristics (predicting loopback edge | |
f981f97b | 64 | # as taken) have both very high hitrate and coverage, so it is very useful. |
17d6c819 | 65 | # On the other hand, "exit block" heuristics (predicting exit edges as not |
f981f97b AJ |
66 | # taken) have good hitrate, but poor coverage, so only 3 branches have been |
67 | # predicted. The "loop header" heuristic has problems, since it tends to | |
17d6c819 JH |
68 | # misspredict. |
69 | # | |
70 | # The implementation of this script is somewhat brute force. My awk skills | |
71 | # are limited. | |
72 | ||
73 | function longeval(e) | |
74 | { | |
75 | e = "echo \"scale = 2 ;"e"\" | bc" | |
76 | e | getline res | |
77 | close (e) | |
78 | return res | |
79 | } | |
80 | ||
81 | BEGIN {nnames = 0} | |
82 | ||
83 | /^ .* heuristics: .*.$/ { | |
84 | name=$0 | |
85 | sub (/^ /,"",name) | |
86 | sub (/ heuristics: .*.$/,"",name) | |
87 | if (!(name in branches)) | |
88 | { | |
89 | names[nnames] = name | |
90 | branches[name]=0 | |
91 | counts[name]=0 | |
92 | hits[name]=0 | |
93 | phits[name]=0 | |
94 | nnames++ | |
95 | } | |
96 | branches[name]+=1 | |
97 | } | |
98 | ||
99 | /^ .* heuristics: .*. exec [0-9]* hit [0-9]* (.*.)$/ { | |
100 | name=$0 | |
101 | sub (/^ /,"",name) | |
102 | sub (/ heuristics: .*. exec [0-9]* hit [0-9]* (.*.)$/,"",name) | |
103 | pred=$0 | |
104 | sub (/^ .* heuristics: /,"",pred) | |
105 | sub (/. exec [0-9]* hit [0-9]* (.*.)$/,"",pred) | |
106 | count=$0 | |
107 | sub (/^ .* heuristics: .*. exec /,"",count) | |
108 | sub (/ hit [0-9]* (.*.)$/,"",count) | |
109 | hit=$0 | |
110 | sub (/^ .* heuristics: .*. exec [0-9]* hit /,"",hit) | |
111 | sub (/ (.*.)$/,"",hit) | |
112 | ||
113 | if (int(pred) < 50.0) | |
114 | { | |
ffd15534 | 115 | hit = count"-"hit; |
17d6c819 JH |
116 | } |
117 | counts[name]=counts[name] "+" count | |
118 | hits[name]=hits[name] "+" hit | |
ffd15534 | 119 | phits[name]=phits[name] "+(("hit")<"count"/2)*("count"-("hit"))+(("hit")>="count"/2)*("hit")" |
17d6c819 JH |
120 | |
121 | #BC crashes on long strings. Irritating. | |
92e3cac8 JH |
122 | if (length(counts[name]) > 2000) |
123 | counts[name] = longeval(counts[name]) | |
124 | if (length(hits[name]) > 2000) | |
125 | hits[name] = longeval(hits[name]) | |
126 | if (length(phits[name]) > 2000) | |
127 | phits[name] = longeval(phits[name]) | |
17d6c819 JH |
128 | } |
129 | END { | |
130 | # Heuristics called combined predicts just everything. | |
e961606c JH |
131 | maxcounts = longeval(counts["combined"]) |
132 | maxbranches = branches["combined"] | |
133 | max = names["combined"] | |
17d6c819 JH |
134 | printf("HEURISTICS BRANCHES (REL) HITRATE COVERAGE (REL)\n") |
135 | for (i = 0; i < nnames ; i++) | |
136 | { | |
137 | name = names[i] | |
4edc91ae | 138 | counts[name] = longeval(counts[name]) |
17d6c819 JH |
139 | printf ("%-27s %8i %5.1f%% %6s%%/%6s%% %12s %5.1f%%\n", |
140 | name, | |
141 | branches[name], branches[name] * 100 / maxbranches, | |
4edc91ae JH |
142 | longeval("("hits[name]") * 100 /(" counts[name]"-0.00001)"), |
143 | longeval("("phits[name]") * 100 /(" counts[name]"-0.00001)"), | |
144 | counts[name], longeval(counts[name]" * 100 / ("maxcounts"-0.00001)")) | |
17d6c819 JH |
145 | } |
146 | } |