new_contents: """Disassemble lldb's Driver::MainLoop() functions comparing Xcode 4.1 vs. 4.2's gdb."""
  
  import os, sys
  import unittest2
  import lldb
  import pexpect
  from lldbbench import *
  
  class FlintVsSlateGDBDisassembly(BenchBase):
  
      mydir = os.path.join("benchmarks", "example")
  
      def setUp(self):
          BenchBase.setUp(self)
          self.gdb_41_exe = '/Flint/usr/bin/gdb'
          self.gdb_42_exe = '/Developer/usr/bin/gdb'
          self.exe = self.lldbExec
          self.function = 'Driver::MainLoop()'
          self.gdb_41_avg = None
          self.gdb_42_avg = None
  
      @benchmarks_test
      def test_run_41_then_42(self):
          """Test disassembly on a large function with 4.1 vs. 4.2's gdb."""
          print
          self.run_gdb_disassembly(self.gdb_41_exe, self.exe, self.function, 5)
          print "4.1 gdb benchmark:", self.stopwatch
          self.gdb_41_avg = self.stopwatch.avg()
          self.run_gdb_disassembly(self.gdb_42_exe, self.exe, self.function, 5)
          print "4.2 gdb benchmark:", self.stopwatch
          self.gdb_42_avg = self.stopwatch.avg()
          print "gdb_42_avg/gdb_41_avg: %f" % (self.gdb_42_avg/self.gdb_41_avg)
  
      @benchmarks_test
      def test_run_42_then_41(self):
          """Test disassembly on a large function with 4.1 vs. 4.2's gdb."""
          print
          self.run_gdb_disassembly(self.gdb_42_exe, self.exe, self.function, 5)
          print "4.2 gdb benchmark:", self.stopwatch
          self.gdb_42_avg = self.stopwatch.avg()
          self.run_gdb_disassembly(self.gdb_41_exe, self.exe, self.function, 5)
          print "4.1 gdb benchmark:", self.stopwatch
          self.gdb_41_avg = self.stopwatch.avg()
          print "gdb_42_avg/gdb_41_avg: %f" % (self.gdb_42_avg/self.gdb_41_avg)
  
      def run_gdb_disassembly(self, gdb_exe_path, exe, function, count):
          # Set self.child_prompt, which is "(gdb) ".
          self.child_prompt = '(gdb) '
          prompt = self.child_prompt
  
          # So that the child gets torn down after the test.
          self.child = pexpect.spawn('%s %s' % (gdb_exe_path, exe))
          child = self.child
  
          # Turn on logging for what the child sends back.
          if self.TraceOn():
              child.logfile_read = sys.stdout
  
          child.expect_exact(prompt)
          child.sendline('break %s' % function)
          child.expect_exact(prompt)
          child.sendline('run')
          child.expect_exact(prompt)
  
          # Reset the stopwatch now.
          self.stopwatch.reset()
          for i in range(count):
              with self.stopwatch:
                  # Disassemble the function.
                  child.sendline('disassemble')
                  child.expect_exact(prompt)
              child.sendline('next')
              child.expect_exact(prompt)
  
          child.sendline('quit')
          child.expect_exact('The program is running.  Exit anyway?')
          child.sendline('y')
          try:
              self.child.expect(pexpect.EOF)
          except:
              pass
  
          if self.TraceOn():
              print "gdb disassembly benchmark:", str(self.stopwatch)
          self.child = None
  
  
  if __name__ == '__main__':
      import atexit
      lldb.SBDebugger.Initialize()
      atexit.register(lambda: lldb.SBDebugger.Terminate())
      unittest2.main()
  
subject: Check in a customized benchmark which compares the Xcode 4.1 vs. Xcode 4.2's gdb disassembly speed on lldb's Driver::MainLoop function which is ~1190 lines of x86 assembly code. This file is not exercised during the normal test suite run, i.e., no +b option specified. So it should be ok.