#!/bin/bash # # findoptdiff # # This script helps find the optimization difference between two llvm # builds. It is useful when you have a build that is known to work and # one that exhibits an optimization problem. Identifying the difference # between the two builds can lead to discovery of the source of a # mis-optimization. # # The script takes two llvm build paths as arguments. These specify the # the two llvm builds to compare. It is generally expected that they # are "close cousins". That is, they are the same except that the # second build contains some experimental optimization features that # are suspected of producing a misoptimization. # # The script takes two bytecode files, one from each build. They are # presumed to be a compilation of the same program or program fragment # with the only difference being the builds. # # The script operates by iteratively applying the optimizations that gccas # and gccld run until there is a difference in the assembly resulting # from the optimization. The difference is then reported with the set of # optimization passes that produce the difference. The processing # continues until all optimization passes have been tried. The differences # for each pass, if they do differ, are placed in a diffs.# file. # # To work around differences in the assembly language format, the script # can also take two filter arguments that post-process the assembly # so they can be differenced without making false positives for known # differences in the two builds. These filters are optional. # # Usage: # findoptdiff llvm1 llvm2 bc1 bc2 filter1 filter2 # # Where: # llvm1 # is the path to the first llvm build dir # llvm2 # is the path to the second llvm build dir # bc1 # is the bytecode file for the first llvm environment # bc2 # is the bytecode file for the second llvm environment # filter1 # is an optional filter for filtering the llvm1 generated assembly # filter2 # is an optional filter for filtering the llvm2 generated assembly # llvm1=$1 llvm2=$2 bc1=$3 bc2=$4 filt1=$5 filt2=$6 if [ -z "$filt1" ] ; then filt1="cat" fi if [ -z "$filt2" ] ; then filt2="cat" fi opt1="${bc1}.opt" opt2="${bc2}.opt" ll1="${bc1}.ll" ll2="${bc2}.ll" opt1ll="${bc1}.opt.ll" opt2ll="${bc2}.opt.ll" dis1="$llvm1/Debug/bin/llvm-dis" dis2="$llvm2/Debug/bin/llvm-dis" opt1="$llvm1/Debug/bin/opt" opt2="$llvm2/Debug/bin/opt" all_switches="-verify -lowersetjmp -raiseallocs -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" #counter=0 function tryit { switches_to_use="$1" $opt1 $switches_to_use "$bc1" -o - | $dis1 | $filt1 > "$opt1ll" $opt2 $switches_to_use "$bc2" -o - | $dis2 | $filt2 > "$opt2ll" diffs="diffs."$((counter++)) diff "$opt1ll" "$opt2ll" > $diffs if [ $? -ne 0 ] ; then echo echo "Diff fails with these switches:" echo $switches echo "Differences:" head $diffs echo 'Switches:' $switches_to_use >> $diffs else rm $diffs fi return 1 } for sw in $all_switches ; do echo -n " $sw" switches="$switches $sw" if tryit "$switches" ; then break; fi done