RDFDeadCode.h

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//===--- RDFDeadCode.h ----------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// RDF-based generic dead code elimination.
//
// The main interface of this class are functions "collect" and "erase".
// This allows custom processing of the function being optimized by a
// particular consumer. The simplest way to use this class would be to
// instantiate an object, and then simply call "collect" and "erase",
// passing the result of "getDeadInstrs()" to it.
// A more complex scenario would be to call "collect" first, then visit
// all post-increment instructions to see if the address update is dead
// or not, and if it is, convert the instruction to a non-updating form.
// After that "erase" can be called with the set of nodes including both,
// dead defs from the updating instructions and the nodes corresponding
// to the dead instructions.
 
#ifndef RDF_DEADCODE_H
#define RDF_DEADCODE_H
 
#include "llvm/CodeGen/RDFGraph.h"
#include "llvm/CodeGen/RDFLiveness.h"
#include "llvm/ADT/SetVector.h"
 
namespace llvm {
  class MachineRegisterInfo;
 
namespace rdf {
  struct DeadCodeElimination {
    DeadCodeElimination(DataFlowGraph &dfg, MachineRegisterInfo &mri)
      : Trace(false), DFG(dfg), MRI(mri), LV(mri, dfg) {}
 
    bool collect();
    bool erase(const SetVector<NodeId> &Nodes);
    void trace(bool On) { Trace = On; }
    bool trace() const { return Trace; }
 
    SetVector<NodeId> getDeadNodes() { return DeadNodes; }
    SetVector<NodeId> getDeadInstrs() { return DeadInstrs; }
    DataFlowGraph &getDFG() { return DFG; }
 
  private:
    bool Trace;
    SetVector<NodeId> LiveNodes;
    SetVector<NodeId> DeadNodes;
    SetVector<NodeId> DeadInstrs;
    DataFlowGraph &DFG;
    MachineRegisterInfo &MRI;
    Liveness LV;
 
    template<typename T> struct SetQueue;
 
    bool isLiveInstr(NodeAddr<StmtNode*> S) const;
    void scanInstr(NodeAddr<InstrNode*> IA, SetQueue<NodeId> &WorkQ);
    void processDef(NodeAddr<DefNode*> DA, SetQueue<NodeId> &WorkQ);
    void processUse(NodeAddr<UseNode*> UA, SetQueue<NodeId> &WorkQ);
  };
} // namespace rdf
} // namespace llvm
 
#endif