passes/proc/proc_rmdead.cc

   1 /*
   2  *  yosys -- Yosys Open SYnthesis Suite
   3  *
   4  *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
   5  *
   6  *  Permission to use, copy, modify, and/or distribute this software for any
   7  *  purpose with or without fee is hereby granted, provided that the above
   8  *  copyright notice and this permission notice appear in all copies.
   9  *
  10  *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  *
  18  */
  19
  20 #include "kernel/register.h"
  21 #include "kernel/bitpattern.h"
  22 #include "kernel/log.h"
  23 #include <sstream>
  24 #include <stdlib.h>
  25 #include <stdio.h>
  26 #include <set>
  27
  28 static void proc_rmdead(RTLIL::SwitchRule *sw, int &counter)
  29 {
  30         BitPatternPool pool(sw->signal);
  31
  32         for (size_t i = 0; i < sw->cases.size(); i++)
  33         {
  34                 bool is_default = SIZE(sw->cases[i]->compare) == 0 && (!pool.empty() || SIZE(sw->signal) == 0);
  35
  36                 for (size_t j = 0; j < sw->cases[i]->compare.size(); j++) {
  37                         RTLIL::SigSpec sig = sw->cases[i]->compare[j];
  38                         if (!sig.is_fully_const())
  39                                 continue;
  40                         if (!pool.take(sig))
  41                                 sw->cases[i]->compare.erase(sw->cases[i]->compare.begin() + (j--));
  42                 }
  43
  44                 if (!is_default) {
  45                         if (sw->cases[i]->compare.size() == 0) {
  46                                 delete sw->cases[i];
  47                                 sw->cases.erase(sw->cases.begin() + (i--));
  48                                 counter++;
  49                                 continue;
  50                         }
  51                         if (pool.empty())
  52                                 sw->cases[i]->compare.clear();
  53                 }
  54
  55                 for (auto switch_it : sw->cases[i]->switches)
  56                         proc_rmdead(switch_it, counter);
  57
  58                 if (is_default)
  59                         pool.take_all();
  60         }
  61 }
  62
  63 struct ProcRmdeadPass : public Pass {
  64         ProcRmdeadPass() : Pass("proc_rmdead", "eliminate dead trees in decision trees") { }
  65         virtual void help()
  66         {
  67                 //   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
  68                 log("\n");
  69                 log("    proc_rmdead [selection]\n");
  70                 log("\n");
  71                 log("This pass identifies unreachable branches in decision trees and removes them.\n");
  72                 log("\n");
  73         }
  74         virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
  75         {
  76                 log_header("Executing PROC_RMDEAD pass (remove dead branches from decision trees).\n");
  77
  78                 extra_args(args, 1, design);
  79
  80                 int total_counter = 0;
  81                 for (auto mod : design->modules()) {
  82                         if (!design->selected(mod))
  83                                 continue;
  84                         for (auto &proc_it : mod->processes) {
  85                                 if (!design->selected(mod, proc_it.second))
  86                                         continue;
  87                                 int counter = 0;
  88                                 for (auto switch_it : proc_it.second->root_case.switches)
  89                                         proc_rmdead(switch_it, counter);
  90                                 if (counter > 0)
  91                                         log("Removed %d dead cases from process %s in module %s.\n", counter,
  92                                                         proc_it.first.c_str(), log_id(mod));
  93                                 total_counter += counter;
  94                         }
  95                 }
  96
  97                 log("Removed a total of %d dead cases.\n", total_counter);
  98         }
  99 } ProcRmdeadPass;
 100