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      1 //===--- RDFDeadCode.h ----------------------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // RDF-based generic dead code elimination.
     11 //
     12 // The main interface of this class are functions "collect" and "erase".
     13 // This allows custom processing of the function being optimized by a
     14 // particular consumer. The simplest way to use this class would be to
     15 // instantiate an object, and then simply call "collect" and "erase",
     16 // passing the result of "getDeadInstrs()" to it.
     17 // A more complex scenario would be to call "collect" first, then visit
     18 // all post-increment instructions to see if the address update is dead
     19 // or not, and if it is, convert the instruction to a non-updating form.
     20 // After that "erase" can be called with the set of nodes including both,
     21 // dead defs from the updating instructions and the nodes corresponding
     22 // to the dead instructions.
     23 
     24 #ifndef RDF_DEADCODE_H
     25 #define RDF_DEADCODE_H
     26 
     27 #include "RDFGraph.h"
     28 #include "RDFLiveness.h"
     29 #include "llvm/ADT/SetVector.h"
     30 
     31 namespace llvm {
     32   class MachineRegisterInfo;
     33 
     34 namespace rdf {
     35   struct DeadCodeElimination {
     36     DeadCodeElimination(DataFlowGraph &dfg, MachineRegisterInfo &mri)
     37       : Trace(false), DFG(dfg), MRI(mri), LV(mri, dfg) {}
     38 
     39     bool collect();
     40     bool erase(const SetVector<NodeId> &Nodes);
     41     void trace(bool On) { Trace = On; }
     42     bool trace() const { return Trace; }
     43 
     44     SetVector<NodeId> getDeadNodes() { return DeadNodes; }
     45     SetVector<NodeId> getDeadInstrs() { return DeadInstrs; }
     46     DataFlowGraph &getDFG() { return DFG; }
     47 
     48   private:
     49     bool Trace;
     50     SetVector<NodeId> LiveNodes;
     51     SetVector<NodeId> DeadNodes;
     52     SetVector<NodeId> DeadInstrs;
     53     DataFlowGraph &DFG;
     54     MachineRegisterInfo &MRI;
     55     Liveness LV;
     56 
     57     template<typename T> struct SetQueue;
     58 
     59     bool isLiveInstr(const MachineInstr *MI) const;
     60     void scanInstr(NodeAddr<InstrNode*> IA, SetQueue<NodeId> &WorkQ);
     61     void processDef(NodeAddr<DefNode*> DA, SetQueue<NodeId> &WorkQ);
     62     void processUse(NodeAddr<UseNode*> UA, SetQueue<NodeId> &WorkQ);
     63   };
     64 } // namespace rdf
     65 } // namespace llvm
     66 
     67 #endif
     68