Provide a script that can track down which optimization pass causes

different code to be produced between two llvm builds that differe slightly.
This is useful in tracking down mis-optimization bugs.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32435 91177308-0d34-0410-b5e6-96231b3b80d8

utils/findoptdiff

@@ -0,0 +1,99 @@
+#!/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. 
+#
+#      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=$5
+if [ -z "$filt1" ] ; then
+  filt1="cat"
+fi
+filt2=$6
+if [ -z "$filt2" ] ; then
+  filt2="cat"
+fi
+opt1=opt.$bc1
+opt2=opt.$bc2
+ll1=${bc1}.ll
+ll2=${bc2}.ll
+dir1="/proj/llvm/llvm-test-1/External/SPEC/CINT2000/300.twolf"
+opt1="/proj/llvm/llvm-1/Debug/bin/opt"
+dis1="/proj/llvm/llvm-1/Debug/bin/llvm-dis"
+dir2="/proj/llvm/llvm-test-2/External/SPEC/CINT2000/300.twolf"
+opt2="/proj/llvm/llvm-2/Debug/bin/opt"
+dis2="/proj/llvm/llvm-2/Debug/bin/llvm-dis"
+bcfile="Output/300.twolf.linked.rbc"
+optll="opt.ll"
+
+all_switches="-verify -lowersetjmp -funcresolve -raiseallocs -simplifycfg -mem2reg -globalopt -globaldce -ipconstprop -deadargelim -instcombine -simplifycfg -prune-eh -inline -simplify-libcalls -argpromotion -raise -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 -funcresolve -internalize -ipsccp -globalopt -constmerge -deadargelim -inline -prune-eh -globalopt -globaldce -argpromotion -instcombine -predsimplify -scalarrepl -globalsmodref-aa -licm -load-vn -gcse -dse -instcombine -simplifycfg -verify"
+
+function tryit {
+  switches_to_use="$1"
+  cd $dir1
+  $opt1 $switches_to_use "$bcfile" -o - | $dis1 | $filt1 > "$optll"
+  cd $dir2
+  $opt2 $switches_to_use "$bcfile" -o - | $dis2 | $filt2 > "$optll"
+  diff "$dir1/$optll" "$dir2/$optll" > /dev/null
+  if [ $? -ne 0 ] ; then
+    echo
+    echo "Diff fails with these switches:"
+    echo $switches
+    echo "Differences:"
+    diff "$dir1/$optll" "$dir2/$optll" | head
+    exit 1
+  fi
+  return 1
+}
+
+for sw in $all_switches ; do
+  echo -n " $sw"
+  switches="$switches $sw"
+  if tryit "$switches" ; then
+    break;
+  fi
+done