* analyze_brprob: New file.

From-SVN: r43252

contrib/ChangeLog

+Tue Jun 12 12:21:40 CEST 2001  Jan Hubicka  <jh@suse.cz>
+
+	* analyze_brprob: New file.
+
 2001-06-11  Mark Mitchell  <mark@codesourcery.com>
 
 	* gcc_build: Output information about the commands used to 

contrib/analyze_brprob

+#!/usr/bin/awk -f
+# Script to analyze experimental results of our branch prediction heursitics
+# Contributed by Jan Hubicka, SuSE inc.
+# Copyright (C) 2001 Free Software Foundation, Inc.
+#
+# This file is part of GNU CC.
+#
+# GNU CC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2, or (at your option)
+# any later version.
+#
+# GNU CC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GNU CC; see the file COPYING.  If not, write to
+# the Free Software Foundation, 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+#
+#
+# This script is used to calculate two basic properties of the branch prediction
+# heursitics - coverage and hitrate.  Coverage is number of executions of given
+# branch matched by the heuristics and hitrate is probability that once branch is
+# predicted as taken it is really taken.
+#
+# These values are usefull to determine quality of given heuristics and hitrate
+# may be directly used in predict.c.
+#
+# Usage:
+#  step 1: compile and profile your program.  You need to use -fprofile-arcs
+#    flag to get the profiles
+#  step 2: Generate log files.  The information about given heuristics are
+#    saved into *.life dumps.  You need to pass -df swtich to compiler as well
+#    as -fbranch-probabilities to get results of profiling noted in the dumps.
+#    Ensure that there is no "Arc profiling: some edge counts were bad." warnings.
+#    Keep the -fprofile-arcs switch to ensure that CFGs match.
+#  step 3: Run this script to concatetation of all *.life files:
+#    analyze_brprob `find . -name *.life`
+#    the information is collected and print once all files are parsed.  This
+#    may take a while.
+#    Note that script does use bc to perform long arithmetic.
+#  step 4: Read the results.  Basically following table is printed:
+#  (this is just example from very early stages of branch prediction pass
+#   development, so please don't take these numbers seriously)
+#
+#HEURISTICS                  BRANCHES  (REL)  HITRATE             COVERAGE  (REL)
+#opcode                          2889  83.7%  94.96%/ 97.62%      7516383  75.3%
+#pointer                          246   7.1%  99.69%/ 99.86%       118791   1.2%
+#loop header                      449  13.0%  98.32%/ 99.07%        43553   0.4%
+#first match                     3450 100.0%  89.92%/ 97.27%      9979782 100.0%
+#loop exit                        924  26.8%  88.95%/ 95.58%      9026266  90.4%
+#error return                     150   4.3%  64.48%/ 86.81%       453542   4.5%
+#call                             803  23.3%  51.66%/ 98.61%      3614037  36.2%
+#loop branch                       51   1.5%  99.26%/ 99.27%        26854   0.3%
+#noreturn call                    951  27.6% 100.00%/100.00%      1759809  17.6%
+#
+#  The heuristics called "first match" is heuristics used by gcc branch
+#  prediction pass and it predicts 89.92% branches correctly.  
+#
+#  The quality of heuristics can be rated using both, coverage and hitrate
+#  parameters.  For example "loop branch" heuristics (predicting loopback edge
+#  as taken) have both very high hitrate and coverage, so it is very usefull.
+#  On the other hand, "exit block" heuristics (predicting exit edges as not
+#  taken) have good hitrate, but poor coverage, so only 3 branches has been
+#  predicted.  The "loop header" heuristics have problem, since it tends to
+#  misspredict.
+#
+#  The implementation of this script is somewhat brute force.  My awk skills
+#  are limited.
+
+function longeval(e)
+{
+  e = "echo \"scale = 2 ;"e"\" | bc"
+  e | getline res
+  close (e)
+  return res
+}
+
+BEGIN {nnames = 0}
+
+/^  .* heuristics: .*.$/ {
+    name=$0
+    sub (/^  /,"",name)
+    sub (/ heuristics: .*.$/,"",name)
+    if (!(name in branches))
+      {
+	names[nnames] = name
+	branches[name]=0
+	counts[name]=0
+	hits[name]=0
+	phits[name]=0
+	nnames++
+      }
+    branches[name]+=1
+  }
+
+/^  .* heuristics: .*. exec [0-9]* hit [0-9]* (.*.)$/ {
+    name=$0
+    sub (/^  /,"",name)
+    sub (/ heuristics: .*. exec [0-9]* hit [0-9]* (.*.)$/,"",name)
+    pred=$0
+    sub (/^  .* heuristics: /,"",pred)
+    sub (/. exec [0-9]* hit [0-9]* (.*.)$/,"",pred)
+    count=$0
+    sub (/^  .* heuristics: .*. exec /,"",count)
+    sub (/ hit [0-9]* (.*.)$/,"",count)
+    hit=$0
+    sub (/^  .* heuristics: .*. exec [0-9]* hit /,"",hit)
+    sub (/ (.*.)$/,"",hit)
+
+    if (int(pred) < 50.0)
+      {
+        hit = count - hit;
+      }
+    counts[name]=counts[name] "+" count
+    hits[name]=hits[name] "+" hit
+    if (int (hit) < (int (count) / 2))
+      hit = count - hit;
+    phits[name]=phits[name] "+" hit
+
+    #BC crashes on long strings.  Irritating.
+    if (length(counts[name]) > 4000)
+      {
+	counts[name] = longeval (counts[name])
+	hits[name] = longeval (hits[name])
+	phits[name] = longeval (phits[name])
+      }
+  }
+END {
+  # Heuristics called combined predicts just everything.
+  maxcounts = longeval (counts["first match"])
+  maxbranches = branches["first match"]
+  max = names["firat match"]
+  printf("HEURISTICS                  BRANCHES  (REL)  HITRATE             COVERAGE  (REL)\n")
+  for (i = 0; i < nnames ; i++)
+   {
+     name = names[i]
+     counts[name] = longeval (counts[name])
+     printf ("%-27s %8i %5.1f%% %6s%%/%6s%% %12s %5.1f%%\n",
+	     name,
+	     branches[name], branches[name] * 100 / maxbranches,
+	     longeval ("("hits[name]") * 100 /(" counts[name]"-0.00001)"),
+	     longeval ("("phits[name]") * 100 /(" counts[name]"-0.00001)"),
+	     counts[name], longeval (counts[name]" * 100 / ("maxcounts"-0.00001)"))
+   }
+}