1 //===--- RDFDeadCode.h ----------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // RDF-based generic dead code elimination.
10 //
11 // The main interface of this class are functions "collect" and "erase".
12 // This allows custom processing of the function being optimized by a
13 // particular consumer. The simplest way to use this class would be to
14 // instantiate an object, and then simply call "collect" and "erase",
15 // passing the result of "getDeadInstrs()" to it.
16 // A more complex scenario would be to call "collect" first, then visit
17 // all post-increment instructions to see if the address update is dead
18 // or not, and if it is, convert the instruction to a non-updating form.
19 // After that "erase" can be called with the set of nodes including both,
20 // dead defs from the updating instructions and the nodes corresponding
21 // to the dead instructions.
22 
23 #ifndef RDF_DEADCODE_H
24 #define RDF_DEADCODE_H
25 
26 #include "llvm/CodeGen/RDFGraph.h"
27 #include "llvm/CodeGen/RDFLiveness.h"
28 #include "llvm/ADT/SetVector.h"
29 
30 namespace llvm {
31   class MachineRegisterInfo;
32 
33 namespace rdf {
34   struct DeadCodeElimination {
DeadCodeEliminationDeadCodeElimination35     DeadCodeElimination(DataFlowGraph &dfg, MachineRegisterInfo &mri)
36       : Trace(false), DFG(dfg), MRI(mri), LV(mri, dfg) {}
37 
38     bool collect();
39     bool erase(const SetVector<NodeId> &Nodes);
traceDeadCodeElimination40     void trace(bool On) { Trace = On; }
traceDeadCodeElimination41     bool trace() const { return Trace; }
42 
getDeadNodesDeadCodeElimination43     SetVector<NodeId> getDeadNodes() { return DeadNodes; }
getDeadInstrsDeadCodeElimination44     SetVector<NodeId> getDeadInstrs() { return DeadInstrs; }
getDFGDeadCodeElimination45     DataFlowGraph &getDFG() { return DFG; }
46 
47   private:
48     bool Trace;
49     SetVector<NodeId> LiveNodes;
50     SetVector<NodeId> DeadNodes;
51     SetVector<NodeId> DeadInstrs;
52     DataFlowGraph &DFG;
53     MachineRegisterInfo &MRI;
54     Liveness LV;
55 
56     template<typename T> struct SetQueue;
57 
58     bool isLiveInstr(const MachineInstr *MI) const;
59     void scanInstr(NodeAddr<InstrNode*> IA, SetQueue<NodeId> &WorkQ);
60     void processDef(NodeAddr<DefNode*> DA, SetQueue<NodeId> &WorkQ);
61     void processUse(NodeAddr<UseNode*> UA, SetQueue<NodeId> &WorkQ);
62   };
63 } // namespace rdf
64 } // namespace llvm
65 
66 #endif
67