script_decompile.py

   1 from dom import *
   2 from dataflow import *
   3 from xform import *
   4 from decomp import *
   5 from xform_utils import apply_iterative
   6
   7
   8 def do_propagate(cfg):
   9     analyze_reach_defs(cfg)
  10     make_du_chains(cfg)
  11
  12     # Choose one, expr_propagation is required for true decompilation
  13     #const_propagation(cfg)
  14     #copy_propagation(cfg)
  15     #mem_propagation(cfg)
  16     expr_propagation(cfg)
  17
  18
  19 def dce(cfg):
  20     analyze_live_vars(cfg)
  21     foreach_bblock(cfg, dead_code_elimination)
  22
  23
  24 def structure(cfg):
  25
  26     def _(res):
  27         return 1 if res else 0
  28
  29     cnt = 1
  30     while cnt:
  31         cnt = 0
  32         cnt += _(match_if(cfg))
  33         # Opportunity for applying match_if_else_unjumped arises after
  34         # match_if pass, and we should match all such cases, or they
  35         # will be consumed by match_seq instead.
  36         cnt += apply_iterative(match_if_else_unjumped, (cfg,))
  37         cnt += _(match_ifelse(cfg))
  38         cnt += _(match_if_else_inv_ladder(cfg))
  39         cnt += _(match_if_else_ladder(cfg))
  40         cnt += _(match_while(cfg))
  41         cnt += _(match_dowhile(cfg))
  42         cnt += _(match_if_dowhile(cfg))
  43         cnt += _(match_seq(cfg))
  44
  45
  46 # Apply arch-specific transformations
  47 def arch_specific(cfg):
  48     # Remove Xtensa memw instructions. TODO: should instead be used to
  49     # recover volatile types.
  50     foreach_bblock(cfg, remove_sfunc, name="memw")
  51
  52
  53 def apply(cfg):
  54     #
  55     # Data flow
  56     #
  57
  58     # Various algos below don't work with no explicit entry in CFG
  59     cfg_preheader(cfg)
  60     # Also don't work with >1 entries
  61     remove_unreachable_entries(cfg)
  62     # Various algos below require single-exit CFG
  63     cfg_single_exit(cfg)
  64
  65     foreach_inst(cfg, sub_const_to_add)
  66     foreach_inst(cfg, rewrite_complex_dest)
  67     foreach_inst(cfg, booleanize_cond)
  68     # Initial pass on simplifying expressions
  69     foreach_inst(cfg, simplify_inst)
  70
  71     analyze_live_vars(cfg)
  72     insert_initial_regs(cfg)
  73
  74     do_propagate(cfg)
  75
  76     # Estimate args only at the beginning of processing
  77     analyze_live_vars(cfg)
  78     estimate_params(cfg)
  79
  80     dce(cfg)
  81
  82     # This should be run after propagation, so it caught all cases.
  83     # Run this after DCE to not do useless work ;-).
  84     foreach_inst(cfg, normalize_cond)
  85
  86     #
  87     # Control flow
  88     #
  89
  90     remove_trailing_jumps(cfg)
  91     remove_jump_over_jump(cfg)
  92
  93     arch_specific(cfg)
  94
  95     cfg.number_postorder()
  96     compute_idom(cfg)
  97     structure(cfg)
  98
  99     # match_abnormal_sel() requires updated DFS numbers
 100     cfg.number_postorder()
 101     # We can't know which node to split before we start control flow processing,
 102     # but splitting node changes data flow, so need to recompute it
 103     if match_abnormal_sel(cfg):
 104
 105         do_propagate(cfg)
 106         dce(cfg)
 107
 108         cfg.number_postorder()
 109         compute_idom(cfg)
 110         structure(cfg)
 111
 112     #
 113     # Post-processing
 114     #
 115
 116     foreach_inst(cfg, rewrite_stack_vars)