utils/findoptdiff

   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 #
  50 llvm1=$1
  51 llvm2=$2
  52 bc1=$3
  53 bc2=$4
  54 filt1=$5
  55 filt2=$6
  56 if [ -z "$filt1" ] ; then
  57   filt1="cat"
  58 fi
  59 if [ -z "$filt2" ] ; then
  60   filt2="cat"
  61 fi
  62 opt1="${bc1}.opt"
  63 opt2="${bc2}.opt"
  64 ll1="${bc1}.ll"
  65 ll2="${bc2}.ll"
  66 opt1ll="${bc1}.opt.ll"
  67 opt2ll="${bc2}.opt.ll"
  68 dis1="$llvm1/Debug/bin/llvm-dis"
  69 dis2="$llvm2/Debug/bin/llvm-dis"
  70 opt1="$llvm1/Debug/bin/opt"
  71 opt2="$llvm2/Debug/bin/opt"
  72
  73 all_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
  76 function 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
  95 for sw in $all_switches ; do
  96   echo -n " $sw"
  97   switches="$switches $sw"
  98   if tryit "$switches" ; then
  99     break;
 100   fi
 101 done