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