1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
|
//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the LoopInfo class that is used to identify natural loops
// and determine the loop depth of various nodes of the CFG. Note that natural
// loops may actually be several loops that share the same header node.
//
// This analysis calculates the nesting structure of loops in a function. For
// each natural loop identified, this analysis identifies natural loops
// contained entirely within the loop and the basic blocks the make up the loop.
//
// It can calculate on the fly various bits of information, for example:
//
// * whether there is a preheader for the loop
// * the number of back edges to the header
// * whether or not a particular block branches out of the loop
// * the successor blocks of the loop
// * the loop depth
// * the trip count
// * etc...
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LOOP_INFO_H
#define LLVM_ANALYSIS_LOOP_INFO_H
#include "llvm/Pass.h"
#include "llvm/ADT/GraphTraits.h"
namespace llvm {
class DominatorTree;
class LoopInfo;
class PHINode;
class Instruction;
//===----------------------------------------------------------------------===//
/// Loop class - Instances of this class are used to represent loops that are
/// detected in the flow graph
///
class Loop {
Loop *ParentLoop;
std::vector<Loop*> SubLoops; // Loops contained entirely within this one
std::vector<BasicBlock*> Blocks; // First entry is the header node
Loop(const Loop &); // DO NOT IMPLEMENT
const Loop &operator=(const Loop &); // DO NOT IMPLEMENT
public:
/// Loop ctor - This creates an empty loop.
Loop() : ParentLoop(0) {}
~Loop() {
for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
delete SubLoops[i];
}
unsigned getLoopDepth() const {
unsigned D = 0;
for (const Loop *CurLoop = this; CurLoop; CurLoop = CurLoop->ParentLoop)
++D;
return D;
}
BasicBlock *getHeader() const { return Blocks.front(); }
Loop *getParentLoop() const { return ParentLoop; }
/// contains - Return true of the specified basic block is in this loop
///
bool contains(const BasicBlock *BB) const;
/// iterator/begin/end - Return the loops contained entirely within this loop.
///
const std::vector<Loop*> &getSubLoops() const { return SubLoops; }
typedef std::vector<Loop*>::const_iterator iterator;
iterator begin() const { return SubLoops.begin(); }
iterator end() const { return SubLoops.end(); }
/// getBlocks - Get a list of the basic blocks which make up this loop.
///
const std::vector<BasicBlock*> &getBlocks() const { return Blocks; }
typedef std::vector<BasicBlock*>::const_iterator block_iterator;
block_iterator block_begin() const { return Blocks.begin(); }
block_iterator block_end() const { return Blocks.end(); }
/// isLoopExit - True if terminator in the block can branch to another block
/// that is outside of the current loop.
///
bool isLoopExit(const BasicBlock *BB) const;
/// getNumBackEdges - Calculate the number of back edges to the loop header
///
unsigned getNumBackEdges() const;
/// isLoopInvariant - Return true if the specified value is loop invariant
///
bool isLoopInvariant(Value *V) const;
//===--------------------------------------------------------------------===//
// APIs for simple analysis of the loop.
//
// Note that all of these methods can fail on general loops (ie, there may not
// be a preheader, etc). For best success, the loop simplification and
// induction variable canonicalization pass should be used to normalize loops
// for easy analysis. These methods assume canonical loops.
/// getExitingBlocks - Return all blocks inside the loop that have successors
/// outside of the loop. These are the blocks _inside of the current loop_
/// which branch out. The returned list is always unique.
///
void getExitingBlocks(std::vector<BasicBlock*> &Blocks) const;
/// getExitBlocks - Return all of the successor blocks of this loop. These
/// are the blocks _outside of the current loop_ which are branched to.
///
void getExitBlocks(std::vector<BasicBlock*> &Blocks) const;
/// getUniqueExitBlocks - Return all unique successor blocks of this loop.
/// These are the blocks _outside of the current loop_ which are branched to.
/// This assumes that loop is in canonical form.
///
void getUniqueExitBlocks(std::vector<BasicBlock*> &ExitBlocks) const;
/// getLoopPreheader - If there is a preheader for this loop, return it. A
/// loop has a preheader if there is only one edge to the header of the loop
/// from outside of the loop. If this is the case, the block branching to the
/// header of the loop is the preheader node.
///
/// This method returns null if there is no preheader for the loop.
///
BasicBlock *getLoopPreheader() const;
/// getLoopLatch - If there is a latch block for this loop, return it. A
/// latch block is the canonical backedge for a loop. A loop header in normal
/// form has two edges into it: one from a preheader and one from a latch
/// block.
BasicBlock *getLoopLatch() const;
/// getCanonicalInductionVariable - Check to see if the loop has a canonical
/// induction variable: an integer recurrence that starts at 0 and increments
/// by one each time through the loop. If so, return the phi node that
/// corresponds to it.
///
PHINode *getCanonicalInductionVariable() const;
/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
/// the canonical induction variable value for the "next" iteration of the
/// loop. This always succeeds if getCanonicalInductionVariable succeeds.
///
Instruction *getCanonicalInductionVariableIncrement() const;
/// getTripCount - Return a loop-invariant LLVM value indicating the number of
/// times the loop will be executed. Note that this means that the backedge
/// of the loop executes N-1 times. If the trip-count cannot be determined,
/// this returns null.
///
Value *getTripCount() const;
/// isLCSSAForm - Return true if the Loop is in LCSSA form
bool isLCSSAForm() const;
//===--------------------------------------------------------------------===//
// APIs for updating loop information after changing the CFG
//
/// addBasicBlockToLoop - This method is used by other analyses to update loop
/// information. NewBB is set to be a new member of the current loop.
/// Because of this, it is added as a member of all parent loops, and is added
/// to the specified LoopInfo object as being in the current basic block. It
/// is not valid to replace the loop header with this method.
///
void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI);
/// replaceChildLoopWith - This is used when splitting loops up. It replaces
/// the OldChild entry in our children list with NewChild, and updates the
/// parent pointer of OldChild to be null and the NewChild to be this loop.
/// This updates the loop depth of the new child.
void replaceChildLoopWith(Loop *OldChild, Loop *NewChild);
/// addChildLoop - Add the specified loop to be a child of this loop. This
/// updates the loop depth of the new child.
///
void addChildLoop(Loop *NewChild);
/// removeChildLoop - This removes the specified child from being a subloop of
/// this loop. The loop is not deleted, as it will presumably be inserted
/// into another loop.
Loop *removeChildLoop(iterator OldChild);
/// addBlockEntry - This adds a basic block directly to the basic block list.
/// This should only be used by transformations that create new loops. Other
/// transformations should use addBasicBlockToLoop.
void addBlockEntry(BasicBlock *BB) {
Blocks.push_back(BB);
}
/// moveToHeader - This method is used to move BB (which must be part of this
/// loop) to be the loop header of the loop (the block that dominates all
/// others).
void moveToHeader(BasicBlock *BB) {
if (Blocks[0] == BB) return;
for (unsigned i = 0; ; ++i) {
assert(i != Blocks.size() && "Loop does not contain BB!");
if (Blocks[i] == BB) {
Blocks[i] = Blocks[0];
Blocks[0] = BB;
return;
}
}
}
/// removeBlockFromLoop - This removes the specified basic block from the
/// current loop, updating the Blocks as appropriate. This does not update
/// the mapping in the LoopInfo class.
void removeBlockFromLoop(BasicBlock *BB);
/// verifyLoop - Verify loop structure
void verifyLoop() const;
void print(std::ostream &O, unsigned Depth = 0) const;
void print(std::ostream *O, unsigned Depth = 0) const {
if (O) print(*O, Depth);
}
void dump() const;
private:
friend class LoopInfo;
Loop(BasicBlock *BB) : ParentLoop(0) {
Blocks.push_back(BB);
}
};
//===----------------------------------------------------------------------===//
/// LoopInfo - This class builds and contains all of the top level loop
/// structures in the specified function.
///
class LoopInfo : public FunctionPass {
// BBMap - Mapping of basic blocks to the inner most loop they occur in
std::map<BasicBlock*, Loop*> BBMap;
std::vector<Loop*> TopLevelLoops;
friend class Loop;
public:
static char ID; // Pass identification, replacement for typeid
LoopInfo() : FunctionPass((intptr_t)&ID) {}
~LoopInfo() { releaseMemory(); }
/// iterator/begin/end - The interface to the top-level loops in the current
/// function.
///
typedef std::vector<Loop*>::const_iterator iterator;
iterator begin() const { return TopLevelLoops.begin(); }
iterator end() const { return TopLevelLoops.end(); }
/// getLoopFor - Return the inner most loop that BB lives in. If a basic
/// block is in no loop (for example the entry node), null is returned.
///
Loop *getLoopFor(const BasicBlock *BB) const {
std::map<BasicBlock *, Loop*>::const_iterator I=
BBMap.find(const_cast<BasicBlock*>(BB));
return I != BBMap.end() ? I->second : 0;
}
/// operator[] - same as getLoopFor...
///
const Loop *operator[](const BasicBlock *BB) const {
return getLoopFor(BB);
}
/// getLoopDepth - Return the loop nesting level of the specified block...
///
unsigned getLoopDepth(const BasicBlock *BB) const {
const Loop *L = getLoopFor(BB);
return L ? L->getLoopDepth() : 0;
}
// isLoopHeader - True if the block is a loop header node
bool isLoopHeader(BasicBlock *BB) const {
const Loop *L = getLoopFor(BB);
return L && L->getHeader() == BB;
}
/// runOnFunction - Calculate the natural loop information.
///
virtual bool runOnFunction(Function &F);
virtual void releaseMemory();
void print(std::ostream &O, const Module* = 0) const;
void print(std::ostream *O, const Module* M = 0) const {
if (O) print(*O, M);
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
/// removeLoop - This removes the specified top-level loop from this loop info
/// object. The loop is not deleted, as it will presumably be inserted into
/// another loop.
Loop *removeLoop(iterator I);
/// changeLoopFor - Change the top-level loop that contains BB to the
/// specified loop. This should be used by transformations that restructure
/// the loop hierarchy tree.
void changeLoopFor(BasicBlock *BB, Loop *L);
/// changeTopLevelLoop - Replace the specified loop in the top-level loops
/// list with the indicated loop.
void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop);
/// addTopLevelLoop - This adds the specified loop to the collection of
/// top-level loops.
void addTopLevelLoop(Loop *New) {
assert(New->getParentLoop() == 0 && "Loop already in subloop!");
TopLevelLoops.push_back(New);
}
/// removeBlock - This method completely removes BB from all data structures,
/// including all of the Loop objects it is nested in and our mapping from
/// BasicBlocks to loops.
void removeBlock(BasicBlock *BB);
private:
void Calculate(DominatorTree &DT);
Loop *ConsiderForLoop(BasicBlock *BB, DominatorTree &DT);
void MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent);
void InsertLoopInto(Loop *L, Loop *Parent);
};
// Allow clients to walk the list of nested loops...
template <> struct GraphTraits<const Loop*> {
typedef const Loop NodeType;
typedef std::vector<Loop*>::const_iterator ChildIteratorType;
static NodeType *getEntryNode(const Loop *L) { return L; }
static inline ChildIteratorType child_begin(NodeType *N) {
return N->begin();
}
static inline ChildIteratorType child_end(NodeType *N) {
return N->end();
}
};
template <> struct GraphTraits<Loop*> {
typedef Loop NodeType;
typedef std::vector<Loop*>::const_iterator ChildIteratorType;
static NodeType *getEntryNode(Loop *L) { return L; }
static inline ChildIteratorType child_begin(NodeType *N) {
return N->begin();
}
static inline ChildIteratorType child_end(NodeType *N) {
return N->end();
}
};
} // End llvm namespace
// Make sure that any clients of this file link in LoopInfo.cpp
FORCE_DEFINING_FILE_TO_BE_LINKED(LoopInfo)
#endif
|