1#!/bin/bash 2# 3# findoptdiff 4# 5# This script helps find the optimization difference between two llvm 6# builds. It is useful when you have a build that is known to work and 7# one that exhibits an optimization problem. Identifying the difference 8# between the two builds can lead to discovery of the source of a 9# mis-optimization. 10# 11# The script takes two llvm build paths as arguments. These specify the 12# the two llvm builds to compare. It is generally expected that they 13# are "close cousins". That is, they are the same except that the 14# second build contains some experimental optimization features that 15# are suspected of producing a misoptimization. 16# 17# The script takes two bitcode files, one from each build. They are 18# presumed to be a compilation of the same program or program fragment 19# with the only difference being the builds. 20# 21# The script operates by iteratively applying the optimizations that gccas 22# and gccld run until there is a difference in the assembly resulting 23# from the optimization. The difference is then reported with the set of 24# optimization passes that produce the difference. The processing 25# continues until all optimization passes have been tried. The differences 26# for each pass, if they do differ, are placed in a diffs.# file. 27# 28# To work around differences in the assembly language format, the script 29# can also take two filter arguments that post-process the assembly 30# so they can be differenced without making false positives for known 31# differences in the two builds. These filters are optional. 32# 33# Usage: 34# findoptdiff llvm1 llvm2 bc1 bc2 filter1 filter2 35# 36# Where: 37# llvm1 38# is the path to the first llvm build dir 39# llvm2 40# is the path to the second llvm build dir 41# bc1 42# is the bitcode file for the first llvm environment 43# bc2 44# is the bitcode file for the second llvm environment 45# filter1 46# is an optional filter for filtering the llvm1 generated assembly 47# filter2 48# is an optional filter for filtering the llvm2 generated assembly 49# 50llvm1=$1 51llvm2=$2 52bc1=$3 53bc2=$4 54filt1=$5 55filt2=$6 56if [ -z "$filt1" ] ; then 57 filt1="cat" 58fi 59if [ -z "$filt2" ] ; then 60 filt2="cat" 61fi 62opt1="${bc1}.opt" 63opt2="${bc2}.opt" 64ll1="${bc1}.ll" 65ll2="${bc2}.ll" 66opt1ll="${bc1}.opt.ll" 67opt2ll="${bc2}.opt.ll" 68dis1="$llvm1/Debug/bin/llvm-dis" 69dis2="$llvm2/Debug/bin/llvm-dis" 70opt1="$llvm1/Debug/bin/opt" 71opt2="$llvm2/Debug/bin/opt" 72 73all_switches="-verify -lowersetjmp -simplifycfg -mem2reg -globalopt -globaldce -ipconstprop -deadargelim -instcombine -simplifycfg -prune-eh -inline -simplify-libcalls -argpromotion -tailduplicate -simplifycfg -scalarrepl -instcombine -predsimplify -condprop -tailcallelim -simplifycfg -reassociate -licm -loop-unswitch -instcombine -indvars -loop-unroll -instcombine -load-vn -gcse -sccp -instcombine -condprop -dse -dce -simplifycfg -deadtypeelim -constmerge -internalize -ipsccp -globalopt -constmerge -deadargelim -inline -prune-eh -globalopt -globaldce -argpromotion -instcombine -predsimplify -scalarrepl -globalsmodref-aa -licm -load-vn -gcse -dse -instcombine -simplifycfg -verify" 74 75#counter=0 76function tryit { 77 switches_to_use="$1" 78 $opt1 $switches_to_use "$bc1" -o - | $dis1 | $filt1 > "$opt1ll" 79 $opt2 $switches_to_use "$bc2" -o - | $dis2 | $filt2 > "$opt2ll" 80 diffs="diffs."$((counter++)) 81 diff "$opt1ll" "$opt2ll" > $diffs 82 if [ $? -ne 0 ] ; then 83 echo 84 echo "Diff fails with these switches:" 85 echo $switches 86 echo "Differences:" 87 head $diffs 88 echo 'Switches:' $switches_to_use >> $diffs 89 else 90 rm $diffs 91 fi 92 return 1 93} 94 95for sw in $all_switches ; do 96 echo -n " $sw" 97 switches="$switches $sw" 98 if tryit "$switches" ; then 99 break; 100 fi 101done 102