1 //===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
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 the LoopInfo class that is used to identify natural loops
11 // and determine the loop depth of various nodes of the CFG.  Note that the
12 // loops identified may actually be several natural loops that share the same
13 // header node... not just a single natural loop.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #include "llvm/Analysis/LoopInfo.h"
18 #include "llvm/Constants.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Analysis/Dominators.h"
21 #include "llvm/Assembly/Writer.h"
22 #include "llvm/Support/CFG.h"
23 #include "llvm/Support/Streams.h"
24 #include "llvm/ADT/DepthFirstIterator.h"
25 #include "llvm/ADT/SmallPtrSet.h"
26 #include <algorithm>
27 using namespace llvm;
28 
29 char LoopInfo::ID = 0;
30 static RegisterPass<LoopInfo>
31 X("loops", "Natural Loop Information", true, true);
32 
33 //===----------------------------------------------------------------------===//
34 // Loop implementation
35 //
36 
37 //===----------------------------------------------------------------------===//
38 // LoopInfo implementation
39 //
40 bool LoopInfo::runOnFunction(Function &) {
41   releaseMemory();
42   LI.Calculate(getAnalysis<DominatorTree>().getBase());    // Update
43   return false;
44 }
45 
46 void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
47   AU.setPreservesAll();
48   AU.addRequired<DominatorTree>();
49 }
50