1 //===- llvm/CodeGen/GlobalISel/CSEInfo.h ------------------*- C++ -*-===//
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 /// Provides analysis for continuously CSEing during GISel passes.
10 //
11 //===----------------------------------------------------------------------===//
12 #ifndef LLVM_CODEGEN_GLOBALISEL_CSEINFO_H
13 #define LLVM_CODEGEN_GLOBALISEL_CSEINFO_H
14 
15 #include "llvm/ADT/FoldingSet.h"
16 #include "llvm/CodeGen/CSEConfigBase.h"
17 #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
18 #include "llvm/CodeGen/GlobalISel/GISelWorkList.h"
19 #include "llvm/CodeGen/GlobalISel/Utils.h"
20 #include "llvm/CodeGen/MachineBasicBlock.h"
21 #include "llvm/CodeGen/MachineFunctionPass.h"
22 #include "llvm/IR/PassManager.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Support/Allocator.h"
25 
26 namespace llvm {
27 
28 /// A class that wraps MachineInstrs and derives from FoldingSetNode in order to
29 /// be uniqued in a CSEMap. The tradeoff here is extra memory allocations for
30 /// UniqueMachineInstr vs making MachineInstr bigger.
31 class UniqueMachineInstr : public FoldingSetNode {
32   friend class GISelCSEInfo;
33   const MachineInstr *MI;
34   explicit UniqueMachineInstr(const MachineInstr *MI) : MI(MI) {}
35 
36 public:
37   void Profile(FoldingSetNodeID &ID);
38 };
39 
40 // A CSE config for fully optimized builds.
41 class CSEConfigFull : public CSEConfigBase {
42 public:
43   virtual ~CSEConfigFull() = default;
44   virtual bool shouldCSEOpc(unsigned Opc) override;
45 };
46 
47 // Commonly used for O0 config.
48 class CSEConfigConstantOnly : public CSEConfigBase {
49 public:
50   virtual ~CSEConfigConstantOnly() = default;
51   virtual bool shouldCSEOpc(unsigned Opc) override;
52 };
53 
54 // Returns the standard expected CSEConfig for the given optimization level.
55 // We have this logic here so targets can make use of it from their derived
56 // TargetPassConfig, but can't put this logic into TargetPassConfig directly
57 // because the CodeGen library can't depend on GlobalISel.
58 std::unique_ptr<CSEConfigBase>
59 getStandardCSEConfigForOpt(CodeGenOpt::Level Level);
60 
61 /// The CSE Analysis object.
62 /// This installs itself as a delegate to the MachineFunction to track
63 /// new instructions as well as deletions. It however will not be able to
64 /// track instruction mutations. In such cases, recordNewInstruction should be
65 /// called (for eg inside MachineIRBuilder::recordInsertion).
66 /// Also because of how just the instruction can be inserted without adding any
67 /// operands to the instruction, instructions are uniqued and inserted lazily.
68 /// CSEInfo should assert when trying to enter an incomplete instruction into
69 /// the CSEMap. There is Opcode level granularity on which instructions can be
70 /// CSE'd and for now, only Generic instructions are CSEable.
71 class GISelCSEInfo : public GISelChangeObserver {
72   // Make it accessible only to CSEMIRBuilder.
73   friend class CSEMIRBuilder;
74 
75   BumpPtrAllocator UniqueInstrAllocator;
76   FoldingSet<UniqueMachineInstr> CSEMap;
77   MachineRegisterInfo *MRI = nullptr;
78   MachineFunction *MF = nullptr;
79   std::unique_ptr<CSEConfigBase> CSEOpt;
80   /// Keep a cache of UniqueInstrs for each MachineInstr. In GISel,
81   /// often instructions are mutated (while their ID has completely changed).
82   /// Whenever mutation happens, invalidate the UniqueMachineInstr for the
83   /// MachineInstr
84   DenseMap<const MachineInstr *, UniqueMachineInstr *> InstrMapping;
85 
86   /// Store instructions that are not fully formed in TemporaryInsts.
87   /// Also because CSE insertion happens lazily, we can remove insts from this
88   /// list and avoid inserting and then removing from the CSEMap.
89   GISelWorkList<8> TemporaryInsts;
90 
91   // Only used in asserts.
92   DenseMap<unsigned, unsigned> OpcodeHitTable;
93 
94   bool isUniqueMachineInstValid(const UniqueMachineInstr &UMI) const;
95 
96   void invalidateUniqueMachineInstr(UniqueMachineInstr *UMI);
97 
98   UniqueMachineInstr *getNodeIfExists(FoldingSetNodeID &ID,
99                                       MachineBasicBlock *MBB, void *&InsertPos);
100 
101   /// Allocate and construct a new UniqueMachineInstr for MI and return.
102   UniqueMachineInstr *getUniqueInstrForMI(const MachineInstr *MI);
103 
104   void insertNode(UniqueMachineInstr *UMI, void *InsertPos = nullptr);
105 
106   /// Get the MachineInstr(Unique) if it exists already in the CSEMap and the
107   /// same MachineBasicBlock.
108   MachineInstr *getMachineInstrIfExists(FoldingSetNodeID &ID,
109                                         MachineBasicBlock *MBB,
110                                         void *&InsertPos);
111 
112   /// Use this method to allocate a new UniqueMachineInstr for MI and insert it
113   /// into the CSEMap. MI should return true for shouldCSE(MI->getOpcode())
114   void insertInstr(MachineInstr *MI, void *InsertPos = nullptr);
115 
116 public:
117   GISelCSEInfo() = default;
118 
119   virtual ~GISelCSEInfo();
120 
121   void setMF(MachineFunction &MF);
122 
123   Error verify();
124 
125   /// Records a newly created inst in a list and lazily insert it to the CSEMap.
126   /// Sometimes, this method might be called with a partially constructed
127   /// MachineInstr,
128   //  (right after BuildMI without adding any operands) - and in such cases,
129   //  defer the hashing of the instruction to a later stage.
130   void recordNewInstruction(MachineInstr *MI);
131 
132   /// Use this callback to inform CSE about a newly fully created instruction.
133   void handleRecordedInst(MachineInstr *MI);
134 
135   /// Use this callback to insert all the recorded instructions. At this point,
136   /// all of these insts need to be fully constructed and should not be missing
137   /// any operands.
138   void handleRecordedInsts();
139 
140   /// Remove this inst from the CSE map. If this inst has not been inserted yet,
141   /// it will be removed from the Tempinsts list if it exists.
142   void handleRemoveInst(MachineInstr *MI);
143 
144   void releaseMemory();
145 
146   void setCSEConfig(std::unique_ptr<CSEConfigBase> Opt) {
147     CSEOpt = std::move(Opt);
148   }
149 
150   bool shouldCSE(unsigned Opc) const;
151 
152   void analyze(MachineFunction &MF);
153 
154   void countOpcodeHit(unsigned Opc);
155 
156   void print();
157 
158   // Observer API
159   void erasingInstr(MachineInstr &MI) override;
160   void createdInstr(MachineInstr &MI) override;
161   void changingInstr(MachineInstr &MI) override;
162   void changedInstr(MachineInstr &MI) override;
163 };
164 
165 class TargetRegisterClass;
166 class RegisterBank;
167 
168 // Simple builder class to easily profile properties about MIs.
169 class GISelInstProfileBuilder {
170   FoldingSetNodeID &ID;
171   const MachineRegisterInfo &MRI;
172 
173 public:
174   GISelInstProfileBuilder(FoldingSetNodeID &ID, const MachineRegisterInfo &MRI)
175       : ID(ID), MRI(MRI) {}
176   // Profiling methods.
177   const GISelInstProfileBuilder &addNodeIDOpcode(unsigned Opc) const;
178   const GISelInstProfileBuilder &addNodeIDRegType(const LLT Ty) const;
179   const GISelInstProfileBuilder &addNodeIDRegType(const Register) const;
180 
181   const GISelInstProfileBuilder &
182   addNodeIDRegType(const TargetRegisterClass *RC) const;
183   const GISelInstProfileBuilder &addNodeIDRegType(const RegisterBank *RB) const;
184 
185   const GISelInstProfileBuilder &addNodeIDRegNum(Register Reg) const;
186 
187   const GISelInstProfileBuilder &addNodeIDImmediate(int64_t Imm) const;
188   const GISelInstProfileBuilder &
189   addNodeIDMBB(const MachineBasicBlock *MBB) const;
190 
191   const GISelInstProfileBuilder &
192   addNodeIDMachineOperand(const MachineOperand &MO) const;
193 
194   const GISelInstProfileBuilder &addNodeIDFlag(unsigned Flag) const;
195   const GISelInstProfileBuilder &addNodeID(const MachineInstr *MI) const;
196 };
197 
198 /// Simple wrapper that does the following.
199 /// 1) Lazily evaluate the MachineFunction to compute CSEable instructions.
200 /// 2) Allows configuration of which instructions are CSEd through CSEConfig
201 /// object. Provides a method called get which takes a CSEConfig object.
202 class GISelCSEAnalysisWrapper {
203   GISelCSEInfo Info;
204   MachineFunction *MF = nullptr;
205   bool AlreadyComputed = false;
206 
207 public:
208   /// Takes a CSEConfigBase object that defines what opcodes get CSEd.
209   /// If CSEConfig is already set, and the CSE Analysis has been preserved,
210   /// it will not use the new CSEOpt(use Recompute to force using the new
211   /// CSEOpt).
212   GISelCSEInfo &get(std::unique_ptr<CSEConfigBase> CSEOpt,
213                     bool ReCompute = false);
214   void setMF(MachineFunction &MFunc) { MF = &MFunc; }
215   void setComputed(bool Computed) { AlreadyComputed = Computed; }
216   void releaseMemory() { Info.releaseMemory(); }
217 };
218 
219 /// The actual analysis pass wrapper.
220 class GISelCSEAnalysisWrapperPass : public MachineFunctionPass {
221   GISelCSEAnalysisWrapper Wrapper;
222 
223 public:
224   static char ID;
225   GISelCSEAnalysisWrapperPass();
226 
227   void getAnalysisUsage(AnalysisUsage &AU) const override;
228 
229   const GISelCSEAnalysisWrapper &getCSEWrapper() const { return Wrapper; }
230   GISelCSEAnalysisWrapper &getCSEWrapper() { return Wrapper; }
231 
232   bool runOnMachineFunction(MachineFunction &MF) override;
233 
234   void releaseMemory() override {
235     Wrapper.releaseMemory();
236     Wrapper.setComputed(false);
237   }
238 };
239 
240 } // namespace llvm
241 
242 #endif
243