# opt_local.rb extends the generic methods implemented in the coreopt
# module with target-specific code patterns transformation

class Flow
  # some helper regexp components
  # integer/label
  Intre = '(?:-|loc_|sub_|xref_)?[0-9][0-9a-fA-F]*h?'
  # GP register
  Reg = 'eax|ebx|ecx|edx|edi|esi|ebp'

  Peephole_patterns = [
    # each pattern is an array of regexp on instruction
    ['call ' + Intre, 'pop ' + Reg],
    ['pushfd', 'popfd'],
  ]

  # ignore modifications to ecx that are not used within the flow
  #Semanticless_registers << 'ecx'

  undef peephole
  def peephole
    puts "\n * peephole *"  if $VERBOSE
    return false if self.empty?

    work_in_progress = false

    # try to match every pattern against every instruction of the Flow
    Peephole_patterns.each { |pat|
      self.each_index{ |i|
        subFlow = nil

        if pat.length <= (self.length - i)
          subFlow = self[i, pat.length]

          if subFlow and pattern_match(pat, subFlow)
            # winner !
            puts "    [-] Match #{pat} at #{Expression[self[i].address]}" if $VERBOSE

            subFlow.each { |di| di.backtrace_binding = nil }

            case pat
            # here we list every pattern again, and apply the transformation we want
	    when ['call ' + Intre, 'pop ' + Reg]
              pop = subFlow.last
	      # pop eax -> mov eax
	      pop.opcode = pop.instruction.cpu.opcode_list.find { |op| op.name == 'mov' }
	      pop.instruction.opname = pop.opcode.name
	      # append the address pushed by the call
	      # mov eax, 0x2134
	      pop.instruction.args << Expression[subFlow.first.next_addr]

              pop.add_comment('call/pop')

	      # remove the 'call'
              burn_di(subFlow.first)

	    when ['pushfd', 'popfd']
              burn_di(subFlow.first)
	      burn_di(subFlow.last)

            else raise "Unsupported pattern: #{pat}"
            end

            work_in_progress = true
          end
        end
      }
    }

    # actually remove the instructions marked as unneeded
    purge_burnt!

    # return true if we did match something,
    # which means that the flow should be optimized once again
    work_in_progress
  end

end