1 //===--- RDFDeadCode.h ----------------------------------------------------===//
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
7 //===----------------------------------------------------------------------===//
9 // RDF-based generic dead code elimination.
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.
23 #ifndef RDF_DEADCODE_H
24 #define RDF_DEADCODE_H
27 #include "RDFLiveness.h"
28 #include "llvm/ADT/SetVector.h"
31 class MachineRegisterInfo;
34 struct DeadCodeElimination {
35 DeadCodeElimination(DataFlowGraph &dfg, MachineRegisterInfo &mri)
36 : Trace(false), DFG(dfg), MRI(mri), LV(mri, dfg) {}
39 bool erase(const SetVector<NodeId> &Nodes);
40 void trace(bool On) { Trace = On; }
41 bool trace() const { return Trace; }
43 SetVector<NodeId> getDeadNodes() { return DeadNodes; }
44 SetVector<NodeId> getDeadInstrs() { return DeadInstrs; }
45 DataFlowGraph &getDFG() { return DFG; }
49 SetVector<NodeId> LiveNodes;
50 SetVector<NodeId> DeadNodes;
51 SetVector<NodeId> DeadInstrs;
53 MachineRegisterInfo &MRI;
56 template<typename T> struct SetQueue;
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);