LoopPass.cpp revision 5afdc7d78526622034932e6d07871c7b25d87361 
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    return L1->getLoopDepth() > L2->getLoopDepth();
30  }
31};
32
33// Loop queue used by Loop Pass Manager. This is a wrapper class
34// that hides implemenation detail (use of priority_queue) inside .cpp file.
35class LoopQueue {
36public:
37  inline void push(Loop *L) { LPQ.push(L); }
38  inline void pop() { LPQ.pop(); }
39  inline Loop *top() { return LPQ.top(); }
40  inline bool empty() { return LPQ.empty(); }
41private:
42  std::priority_queue<Loop *, std::vector<Loop *>, LoopCompare> LPQ;
43};
44
45} // End of LLVM namespace
46
47//===----------------------------------------------------------------------===//
48// LPPassManager
49//
50/// LPPassManager manages FPPassManagers and CalLGraphSCCPasses.
51
52LPPassManager::LPPassManager(int Depth) : PMDataManager(Depth) {
53  LQ = new LoopQueue();
54}
55
56LPPassManager::~LPPassManager() {
57  delete LQ;
58}
59
60/// Delete loop from the loop queue. This is used by Loop pass to inform
61/// Loop Pass Manager that it should skip rest of the passes for this loop.
62void LPPassManager::deleteLoopFromQueue(Loop *L) {
63  // Do not pop loop from LQ here. It will be done by runOnFunction while loop.
64  skipThisLoop = true;
65}
66
67// Recurse through all subloops and all loops  into LQ.
68static void addLoopIntoQueue(Loop *L, LoopQueue *LQ) {
69  for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
70    addLoopIntoQueue(*I, LQ);
71  LQ->push(L);
72}
73
74/// run - Execute all of the passes scheduled for execution.  Keep track of
75/// whether any of the passes modifies the function, and if so, return true.
76bool LPPassManager::runOnFunction(Function &F) {
77  LoopInfo &LI = getAnalysis<LoopInfo>();
78  bool Changed = false;
79
80  // Populate Loop Queue
81  for (LoopInfo::iterator I = LI.begin(), E = LI.end(); I != E; ++I)
82    addLoopIntoQueue(*I, LQ);
83
84  std::string Msg1 = "Executing Pass '";
85  std::string Msg3 = "' Made Modification '";
86
87  // Walk Loops
88  while (!LQ->empty()) {
89
90    Loop *L  = LQ->top();
91    skipThisLoop = false;
92
93    // Run all passes on current SCC
94    for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
95
96      Pass *P = getContainedPass(Index);
97      AnalysisUsage AnUsage;
98      P->getAnalysisUsage(AnUsage);
99
100      std::string Msg2 = "' on Loop ...\n'";
101      dumpPassInfo(P, Msg1, Msg2);
102      dumpAnalysisSetInfo("Required", P, AnUsage.getRequiredSet());
103
104      initializeAnalysisImpl(P);
105
106      StartPassTimer(P);
107      LoopPass *LP = dynamic_cast<LoopPass *>(P);
108      assert (LP && "Invalid LPPassManager member");
109      LP->runOnLoop(*L, *this);
110      StopPassTimer(P);
111
112      if (Changed)
113	dumpPassInfo(P, Msg3, Msg2);
114      dumpAnalysisSetInfo("Preserved", P, AnUsage.getPreservedSet());
115
116      removeNotPreservedAnalysis(P);
117      recordAvailableAnalysis(P);
118      removeDeadPasses(P, Msg2);
119
120      if (skipThisLoop)
121        // Do not run other passes on this loop.
122        break;
123    }
124
125    // Pop the loop from queue after running all passes.
126    LQ->pop();
127  }
128
129  return Changed;
130}
131
132
133