live_vregs.h

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// Copyright (c) 2021-2023, David H. Hovemeyer <david.hovemeyer@gmail.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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// OTHER DEALINGS IN THE SOFTWARE.
 
#ifndef LIVE_VREGS_H
#define LIVE_VREGS_H
 
#include <string>
#include "instruction.h"
#include "highlevel_defuse.h"
#include "dataflow.h"
 
 
class LiveVregsAnalysis : public BackwardAnalysis {
public:
  // We assume that there are never more than this many vregs used
  static const unsigned MAX_VREGS = 256;
 
  typedef std::bitset<MAX_VREGS> FactType;
 
  FactType get_top_fact() const { return FactType(); }
 
  FactType combine_facts(const FactType &left, const FactType &right) const {
    return left | right;
  }
 
  void model_instruction(Instruction *ins, FactType &fact) const {
    // Model an instruction (backwards).  If the instruction is a def,
    // the assigned-to vreg is killed.  Every vreg used in the instruction,
    // the vreg becomes alive (or is kept alive.)
 
    if (HighLevel::is_def(ins)) {
      Operand operand = ins->get_operand(0);
      assert(operand.has_base_reg());
      fact.reset(operand.get_base_reg());
    }
 
    for (unsigned i = 0; i < ins->get_num_operands(); i++) {
      if (HighLevel::is_use(ins, i)) {
        Operand operand = ins->get_operand(i); 
 
        assert(operand.has_base_reg());
        fact.set(operand.get_base_reg());
 
        if (operand.has_index_reg()) {
          fact.set(operand.get_index_reg());
        }
      }
    }
  }
 
  std::string fact_to_string(const FactType &fact) const {
    std::string s("{");
    for (unsigned i = 0; i < MAX_VREGS; i++) {
      if (fact.test(i)) {
        if (s != "{") { s += ","; }
        s += std::to_string(i);
      }
    }
    s += "}";
    return s;
  }
};
 
typedef Dataflow<LiveVregsAnalysis> LiveVregs;
 
#endif // LIVE_VREGS_H