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
31namespace llvm {
32  class MachineRegisterInfo;
33
34namespace 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