Add basic delta-debugging script used for reducing analyzer crasher test cases.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@157219 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/analyzer/reducer.pl b/utils/analyzer/reducer.pl
new file mode 100755
index 0000000..f2dac1f
--- /dev/null
+++ b/utils/analyzer/reducer.pl
@@ -0,0 +1,65 @@
+#!/usr/bin/perl -w
+use strict;
+use File::Temp qw/ tempdir /;
+my $prog = "reducer";
+
+die "$prog <code file> <error string> [optional command]\n" if ($#ARGV < 0);
+my $file = shift @ARGV;
+die "$prog: [error] cannot read file $file\n" if (! -r $file);
+
+my $magic = shift @ARGV;
+die "$prog: [error] no error string specified\n" if (! defined $magic);
+
+# Create a backup of the fuke.
+my $dir = tempdir( CLEANUP => 1 );
+print "$prog: created temporary directory '$dir'\n";
+my $srcFile = "$dir/$file";
+`cp $file $srcFile`;
+
+# Create the script.
+my $scriptFile = "$dir/script";
+open(OUT, ">$scriptFile") or die "$prog: cannot create '$scriptFile'\n";
+my $reduceOut = "$dir/reduceOut";
+
+my $command;
+if (scalar(@ARGV) > 0) { $command = \@ARGV; }
+else {
+  my $compiler = "/Users/kremenek/llvm-cmake-release/bin/clang";
+  $command = [$compiler, "-fsyntax-only", "-Wfatal-errors", "-Wno-deprecated-declarations", "-Wimplicit-function-declaration"];
+}
+push @$command, $srcFile;
+my $commandStr = "@$command";
+
+print OUT <<ENDTEXT;
+#!/usr/bin/perl -w
+use strict;
+my \$BAD = 1;
+my \$GOOD = 0;
+`rm -f $reduceOut`;
+my \$command = "$commandStr > $reduceOut 2>&1";
+system(\$command);
+open(IN, "$reduceOut") or exit(\$BAD);
+my \$found = 0;
+while(<IN>) {
+  if (/$magic/) { exit \$GOOD; }
+}
+exit \$BAD;
+ENDTEXT
+close(OUT);
+`chmod +x $scriptFile`;
+
+print "$prog: starting reduction\n";
+sub multidelta {
+    my $level = shift @_;
+    system("multidelta -level=$level $scriptFile $srcFile");
+}
+
+for (my $i = 1 ; $i <= 5; $i++) {
+  foreach my $level (0,0,1,1,2,2,10) {
+    multidelta($level);
+  }
+}
+
+# Copy the final file.
+`cp $srcFile $file.reduced`;
+print "$prog: generated '$file.reduced";