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
30namespace llvm {
31 class MachineRegisterInfo;
32
33namespace rdf {
34 struct DeadCodeElimination {
35 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);
40 void trace(bool On) { Trace = On; }
41 bool trace() const { return Trace; }
42
43 SetVector<NodeId> getDeadNodes() { return DeadNodes; }
44 SetVector<NodeId> getDeadInstrs() { return DeadInstrs; }
45 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(NodeAddr<StmtNode*> S) 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