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-#!/usr/bin/awk -f
-# Script to analyze experimental results of our branch prediction heuristics
-# Contributed by Jan Hubicka, SuSE Inc.
-# Copyright (C) 2001, 2003 Free Software Foundation, Inc.
-#
-# This file is part of GCC.
-#
-# GCC 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 3, or (at your option)
-# any later version.
-#
-# GCC 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 GCC; see the file COPYING. If not, write to
-# the Free Software Foundation, 51 Franklin Street, Fifth Floor,
-# Boston, MA 02110-1301, USA.
-#
-#
-# This script is used to calculate two basic properties of the branch prediction
-# heuristics - coverage and hitrate. Coverage is number of executions of a given
-# branch matched by the heuristics and hitrate is probability that once branch is
-# predicted as taken it is really taken.
-#
-# These values are useful to determine the quality of given heuristics. 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 *.bp dumps. You need to pass the -db switch to the compiler as well
-# as -fbranch-probabilities to get the results of profiling noted in the dumps.
-# Ensure that there are no "Arc profiling: some edge counts were bad." warnings.
-# Step 3: Run this script to concatenate 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 the script does use bc to perform long arithmetic.
-# Step 4: Read the results. Basically the following table is printed:
-# (this is just an example from a very early stage 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 heuristic called "first match" is a heuristic 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 useful.
-# On the other hand, "exit block" heuristics (predicting exit edges as not
-# taken) have good hitrate, but poor coverage, so only 3 branches have been
-# predicted. The "loop header" heuristic has problems, 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
- phits[name]=phits[name] "+(("hit")<"count"/2)*("count"-("hit"))+(("hit")>="count"/2)*("hit")"
-
- #BC crashes on long strings. Irritating.
- if (length(counts[name]) > 2000)
- counts[name] = longeval(counts[name])
- if (length(hits[name]) > 2000)
- hits[name] = longeval(hits[name])
- if (length(phits[name]) > 2000)
- phits[name] = longeval(phits[name])
- }
-END {
- # Heuristics called combined predicts just everything.
- maxcounts = longeval(counts["combined"])
- maxbranches = branches["combined"]
- max = names["combined"]
- printf("HEURISTICS BRANCHES (REL) HITRATE COVERAGE (REL)\n")
- for (i = 0; i < nnames ; i++)
- {
- name = names[i]
- counts[name] = longeval(counts[name])
- printf ("%-26s %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)"))
- }
-}