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 <assert.h>
  27 #include <set>
  28
  29 static void proc_rmdead(RTLIL::SwitchRule *sw, int &counter)
  30 {
  31         BitPatternPool pool(sw->signal);
  32
  33         for (size_t i = 0; i < sw->cases.size(); i++)
  34         {
  35                 bool is_default = sw->cases[i]->compare.size() == 0 && !pool.empty();
  36
  37                 for (size_t j = 0; j < sw->cases[i]->compare.size(); j++) {
  38                         RTLIL::SigSpec sig = sw->cases[i]->compare[j];
  39                         if (!sig.is_fully_const())
  40                                 continue;
  41                         if (!pool.take(sig))
  42                                 sw->cases[i]->compare.erase(sw->cases[i]->compare.begin() + (j--));
  43                 }
  44
  45                 if (!is_default) {
  46                         if (sw->cases[i]->compare.size() == 0) {
  47                                 delete sw->cases[i];
  48                                 sw->cases.erase(sw->cases.begin() + (i--));
  49                                 counter++;
  50                                 continue;
  51                         }
  52                         if (pool.empty())
  53                                 sw->cases[i]->compare.clear();
  54                 }
  55
  56                 for (auto switch_it : sw->cases[i]->switches)
  57                         proc_rmdead(switch_it, counter);
  58
  59                 if (is_default)
  60                         pool.take_all();
  61         }
  62 }
  63
  64 struct ProcRmdeadPass : public Pass {
  65         ProcRmdeadPass() : Pass("proc_rmdead", "eliminate dead trees in decision trees") { }
  66         virtual void help()
  67         {
  68                 //   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
  69                 log("\n");
  70                 log("    proc_rmdead [selection]\n");
  71                 log("\n");
  72                 log("This pass identifies unreachable branches in decision trees and removes them.\n");
  73                 log("\n");
  74         }
  75         virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
  76         {
  77                 log_header("Executing PROC_RMDEAD pass (remove dead branches from decision trees).\n");
  78
  79                 extra_args(args, 1, design);
  80
  81                 int total_counter = 0;
  82                 for (auto &mod_it : design->modules) {
  83                         if (!design->selected(mod_it.second))
  84                                 continue;
  85                         for (auto &proc_it : mod_it.second->processes) {
  86                                 if (!design->selected(mod_it.second, proc_it.second))
  87                                         continue;
  88                                 int counter = 0;
  89                                 for (auto switch_it : proc_it.second->root_case.switches)
  90                                         proc_rmdead(switch_it, counter);
  91                                 if (counter > 0)
  92                                         log("Removed %d dead cases from process %s in module %s.\n", counter,
  93                                                         proc_it.first.c_str(), mod_it.first.c_str());
  94                                 total_counter += counter;
  95                         }
  96                 }
  97
  98                 log("Removed a total of %d dead cases.\n", total_counter);
  99         }
 100 } ProcRmdeadPass;
 101