1 //===- LoopPass.h - LoopPass class ----------------------------------------===//
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 // This file defines LoopPass class. All loop optimization
11 // and transformation passes are derived from LoopPass.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_ANALYSIS_LOOPPASS_H
16 #define LLVM_ANALYSIS_LOOPPASS_H
17 
18 #include "llvm/Analysis/LoopInfo.h"
19 #include "llvm/IR/LegacyPassManagers.h"
20 #include "llvm/Pass.h"
21 #include <deque>
22 
23 namespace llvm {
24 
25 class LPPassManager;
26 class Function;
27 class PMStack;
28 
29 class LoopPass : public Pass {
30 public:
LoopPass(char & pid)31   explicit LoopPass(char &pid) : Pass(PT_Loop, pid) {}
32 
33   /// getPrinterPass - Get a pass to print the function corresponding
34   /// to a Loop.
35   Pass *createPrinterPass(raw_ostream &O,
36                           const std::string &Banner) const override;
37 
38   // runOnLoop - This method should be implemented by the subclass to perform
39   // whatever action is necessary for the specified Loop.
40   virtual bool runOnLoop(Loop *L, LPPassManager &LPM) = 0;
41 
42   using llvm::Pass::doInitialization;
43   using llvm::Pass::doFinalization;
44 
45   // Initialization and finalization hooks.
doInitialization(Loop * L,LPPassManager & LPM)46   virtual bool doInitialization(Loop *L, LPPassManager &LPM) {
47     return false;
48   }
49 
50   // Finalization hook does not supply Loop because at this time
51   // loop nest is completely different.
doFinalization()52   virtual bool doFinalization() { return false; }
53 
54   // Check if this pass is suitable for the current LPPassManager, if
55   // available. This pass P is not suitable for a LPPassManager if P
56   // is not preserving higher level analysis info used by other
57   // LPPassManager passes. In such case, pop LPPassManager from the
58   // stack. This will force assignPassManager() to create new
59   // LPPassManger as expected.
60   void preparePassManager(PMStack &PMS) override;
61 
62   /// Assign pass manager to manage this pass
63   void assignPassManager(PMStack &PMS, PassManagerType PMT) override;
64 
65   ///  Return what kind of Pass Manager can manage this pass.
getPotentialPassManagerType()66   PassManagerType getPotentialPassManagerType() const override {
67     return PMT_LoopPassManager;
68   }
69 
70   //===--------------------------------------------------------------------===//
71   /// SimpleAnalysis - Provides simple interface to update analysis info
72   /// maintained by various passes. Note, if required this interface can
73   /// be extracted into a separate abstract class but it would require
74   /// additional use of multiple inheritance in Pass class hierarchy, something
75   /// we are trying to avoid.
76 
77   /// Each loop pass can override these simple analysis hooks to update
78   /// desired analysis information.
79   /// cloneBasicBlockAnalysis - Clone analysis info associated with basic block.
cloneBasicBlockAnalysis(BasicBlock * F,BasicBlock * T,Loop * L)80   virtual void cloneBasicBlockAnalysis(BasicBlock *F, BasicBlock *T, Loop *L) {}
81 
82   /// deleteAnalysisValue - Delete analysis info associated with value V.
deleteAnalysisValue(Value * V,Loop * L)83   virtual void deleteAnalysisValue(Value *V, Loop *L) {}
84 
85   /// Delete analysis info associated with Loop L.
86   /// Called to notify a Pass that a loop has been deleted and any
87   /// associated analysis values can be deleted.
deleteAnalysisLoop(Loop * L)88   virtual void deleteAnalysisLoop(Loop *L) {}
89 
90 protected:
91   /// skipOptnoneFunction - Containing function has Attribute::OptimizeNone
92   /// and most transformation passes should skip it.
93   bool skipOptnoneFunction(const Loop *L) const;
94 };
95 
96 class LPPassManager : public FunctionPass, public PMDataManager {
97 public:
98   static char ID;
99   explicit LPPassManager();
100 
101   /// run - Execute all of the passes scheduled for execution.  Keep track of
102   /// whether any of the passes modifies the module, and if so, return true.
103   bool runOnFunction(Function &F) override;
104 
105   /// Pass Manager itself does not invalidate any analysis info.
106   // LPPassManager needs LoopInfo.
107   void getAnalysisUsage(AnalysisUsage &Info) const override;
108 
getPassName()109   const char *getPassName() const override {
110     return "Loop Pass Manager";
111   }
112 
getAsPMDataManager()113   PMDataManager *getAsPMDataManager() override { return this; }
getAsPass()114   Pass *getAsPass() override { return this; }
115 
116   /// Print passes managed by this manager
117   void dumpPassStructure(unsigned Offset) override;
118 
getContainedPass(unsigned N)119   LoopPass *getContainedPass(unsigned N) {
120     assert(N < PassVector.size() && "Pass number out of range!");
121     LoopPass *LP = static_cast<LoopPass *>(PassVector[N]);
122     return LP;
123   }
124 
getPassManagerType()125   PassManagerType getPassManagerType() const override {
126     return PMT_LoopPassManager;
127   }
128 
129 public:
130   // Delete loop from the loop queue and loop nest (LoopInfo).
131   void deleteLoopFromQueue(Loop *L);
132 
133   // Insert loop into the loop queue and add it as a child of the
134   // given parent.
135   void insertLoop(Loop *L, Loop *ParentLoop);
136 
137   // Insert a loop into the loop queue.
138   void insertLoopIntoQueue(Loop *L);
139 
140   // Reoptimize this loop. LPPassManager will re-insert this loop into the
141   // queue. This allows LoopPass to change loop nest for the loop. This
142   // utility may send LPPassManager into infinite loops so use caution.
143   void redoLoop(Loop *L);
144 
145   //===--------------------------------------------------------------------===//
146   /// SimpleAnalysis - Provides simple interface to update analysis info
147   /// maintained by various passes. Note, if required this interface can
148   /// be extracted into a separate abstract class but it would require
149   /// additional use of multiple inheritance in Pass class hierarchy, something
150   /// we are trying to avoid.
151 
152   /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
153   /// all passes that implement simple analysis interface.
154   void cloneBasicBlockSimpleAnalysis(BasicBlock *From, BasicBlock *To, Loop *L);
155 
156   /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes
157   /// that implement simple analysis interface.
158   void deleteSimpleAnalysisValue(Value *V, Loop *L);
159 
160   /// Invoke deleteAnalysisLoop hook for all passes that implement simple
161   /// analysis interface.
162   void deleteSimpleAnalysisLoop(Loop *L);
163 
164 private:
165   std::deque<Loop *> LQ;
166   bool skipThisLoop;
167   bool redoThisLoop;
168   LoopInfo *LI;
169   Loop *CurrentLoop;
170 };
171 
172 } // End llvm namespace
173 
174 #endif
175