LoopPass.cpp revision 7f99761143cdf1ad23729708e3dcaa055b189406 
1//===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by Devang Patel and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements LoopPass and LPPassManager. All loop optimization
11// and transformation passes are derived from LoopPass. LPPassManager is
12// responsible for managing LoopPasses.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Analysis/LoopPass.h"
17#include <queue>
18using namespace llvm;
19
20//===----------------------------------------------------------------------===//
21// LoopQueue
22
23namespace llvm {
24
25// Compare Two loops based on their depth in loop nest.
26class LoopCompare {
27public:
28  bool operator()( Loop *L1, Loop *L2) const {
29    // Loops with highest depth has the highest priority.
30    return L1->getLoopDepth() < L2->getLoopDepth();
31  }
32};
33
34// Loop queue used by Loop Pass Manager. This is a wrapper class
35// that hides implemenation detail (use of priority_queue) inside .cpp file.
36class LoopQueue {
37public:
38  inline void push(Loop *L) { LPQ.push(L); }
39  inline void pop() { LPQ.pop(); }
40  inline Loop *top() { return LPQ.top(); }
41  inline bool empty() { return LPQ.empty(); }
42private:
43  std::priority_queue<Loop *, std::vector<Loop *>, LoopCompare> LPQ;
44};
45
46} // End of LLVM namespace
47
48//===----------------------------------------------------------------------===//
49// LPPassManager
50//
51/// LPPassManager manages FPPassManagers and CalLGraphSCCPasses.
52
53LPPassManager::LPPassManager(int Depth) : PMDataManager(Depth) {
54  skipThisLoop = false;
55  redoThisLoop = false;
56  LQ = new LoopQueue();
57}
58
59LPPassManager::~LPPassManager() {
60  delete LQ;
61}
62
63/// Delete loop from the loop queue. This is used by Loop pass to inform
64/// Loop Pass Manager that it should skip rest of the passes for this loop.
65void LPPassManager::deleteLoopFromQueue(Loop *L) {
66  // Do not pop loop from LQ here. It will be done by runOnFunction while loop.
67  skipThisLoop = true;
68}
69
70// Reoptimize this loop. LPPassManager will re-insert this loop into the
71// queue. This allows LoopPass to change loop nest for the loop. This
72// utility may send LPPassManager into infinite loops so use caution.
73void LPPassManager::redoLoop(Loop *L) {
74  redoThisLoop = true;
75}
76
77// Recurse through all subloops and all loops  into LQ.
78static void addLoopIntoQueue(Loop *L, LoopQueue *LQ) {
79  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
80    addLoopIntoQueue(*I, LQ);
81  LQ->push(L);
82}
83
84/// run - Execute all of the passes scheduled for execution.  Keep track of
85/// whether any of the passes modifies the function, and if so, return true.
86bool LPPassManager::runOnFunction(Function &F) {
87  LoopInfo &LI = getAnalysis<LoopInfo>();
88  bool Changed = false;
89
90  // Populate Loop Queue
91  for (LoopInfo::iterator I = LI.begin(), E = LI.end(); I != E; ++I)
92    addLoopIntoQueue(*I, LQ);
93
94  // Walk Loops
95  while (!LQ->empty()) {
96
97    Loop *L  = LQ->top();
98    skipThisLoop = false;
99    redoThisLoop = false;
100
101    // Run all passes on current SCC
102    for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
103
104      Pass *P = getContainedPass(Index);
105      AnalysisUsage AnUsage;
106      P->getAnalysisUsage(AnUsage);
107
108      dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, "");
109      dumpAnalysisSetInfo("Required", P, AnUsage.getRequiredSet());
110
111      initializeAnalysisImpl(P);
112
113      StartPassTimer(P);
114      LoopPass *LP = dynamic_cast<LoopPass *>(P);
115      assert (LP && "Invalid LPPassManager member");
116      LP->runOnLoop(L, *this);
117      StopPassTimer(P);
118
119      if (Changed)
120        dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, "");
121      dumpAnalysisSetInfo("Preserved", P, AnUsage.getPreservedSet());
122
123      removeNotPreservedAnalysis(P);
124      recordAvailableAnalysis(P);
125      removeDeadPasses(P, "", ON_LOOP_MSG);
126
127      if (skipThisLoop)
128        // Do not run other passes on this loop.
129        break;
130    }
131
132    // Pop the loop from queue after running all passes.
133    LQ->pop();
134
135    if (redoThisLoop)
136      LQ->push(L);
137  }
138
139  return Changed;
140}
141
142
143//===----------------------------------------------------------------------===//
144// LoopPass
145
146/// Assign pass manager to manage this pass.
147void LoopPass::assignPassManager(PMStack &PMS,
148                                 PassManagerType PreferredType) {
149  // Find LPPassManager
150  while (!PMS.empty()) {
151    if (PMS.top()->getPassManagerType() > PMT_LoopPassManager)
152      PMS.pop();
153    else;
154    break;
155  }
156
157  LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top());
158
159  // Create new Loop Pass Manager if it does not exist.
160  if (!LPPM) {
161
162    assert (!PMS.empty() && "Unable to create Loop Pass Manager");
163    PMDataManager *PMD = PMS.top();
164
165    // [1] Create new Call Graph Pass Manager
166    LPPM = new LPPassManager(PMD->getDepth() + 1);
167
168    // [2] Set up new manager's top level manager
169    PMTopLevelManager *TPM = PMD->getTopLevelManager();
170    TPM->addIndirectPassManager(LPPM);
171
172    // [3] Assign manager to manage this new manager. This may create
173    // and push new managers into PMS
174    Pass *P = dynamic_cast<Pass *>(LPPM);
175    P->assignPassManager(PMS);
176
177    // [4] Push new manager into PMS
178    PMS.push(LPPM);
179  }
180
181  LPPM->add(this);
182}
183
184