script_i_preserveds.py

   1 from xform import *
   2 from dataflow import *
   3
   4 def apply(cfg):
   5     # script_i_prepare was run before this
   6
   7     analyze_reach_defs(cfg)
   8     # Need to do before DCE and even before insert_initial_regs
   9     collect_reach_exit(cfg)
  10     collect_reach_exit_maybe(cfg)
  11
  12     # analyze_live_vars uses modifieds, so if preserveds is available, we need
  13     # to update modifieds for possible update in reach_exit, otherwise we'll
  14     # have positive feedback in propagation and bad flip-flop effect for preserveds
  15     # value.
  16     if "preserveds" in cfg.props:
  17         modifieds = cfg.props["reach_exit"] - cfg.props["preserveds"]
  18         progdb.update_cfg_prop(cfg, "modifieds", modifieds)
  19
  20     analyze_live_vars(cfg)
  21     insert_initial_regs(cfg)
  22
  23     analyze_reach_defs(cfg)
  24
  25     #const_propagation(cfg)
  26     #copy_propagation(cfg)
  27     #mem_propagation(cfg)
  28     # May infinite-loop without $sp_0, etc.
  29     expr_propagation(cfg)
  30
  31     # To rewrite stack vars, we need to propagate $sp_0, hence all the above
  32     foreach_inst(cfg, rewrite_stack_vars, rewrite_to=REG)
  33
  34     # Now need to do second propagation phase, of stack vars
  35     analyze_reach_defs(cfg)
  36     expr_propagation(cfg)
  37
  38     # Analyze and record preserved registers
  39     collect_preserveds(cfg)
  40
  41     modifieds = cfg.props["reach_exit"] - cfg.props["preserveds"]
  42     progdb.update_cfg_prop(cfg, "modifieds", modifieds)
  43
  44     #
  45     # Argument estimation part
  46     #
  47
  48     # Reanalyze live vars for DCE
  49     analyze_live_vars(cfg)
  50     # Eliminate any preservation assignments, and thus liveness of preserved regs
  51     foreach_bblock(cfg, dead_code_elimination)