1 //===- RegionInfo.cpp - SESE region detection analysis --------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 // Detects single entry single exit regions in the control flow graph.
9 //===----------------------------------------------------------------------===//
10 
11 #include "llvm/Analysis/RegionInfo.h"
12 #include "llvm/ADT/Statistic.h"
13 #include "llvm/Analysis/DominanceFrontier.h"
14 #include "llvm/InitializePasses.h"
15 #ifndef NDEBUG
16 #include "llvm/Analysis/RegionPrinter.h"
17 #endif
18 #include "llvm/Analysis/RegionInfoImpl.h"
19 #include "llvm/Config/llvm-config.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/Support/CommandLine.h"
22 #include "llvm/Support/Compiler.h"
23 
24 using namespace llvm;
25 
26 #define DEBUG_TYPE "region"
27 
28 namespace llvm {
29 
30 template class RegionBase<RegionTraits<Function>>;
31 template class RegionNodeBase<RegionTraits<Function>>;
32 template class RegionInfoBase<RegionTraits<Function>>;
33 
34 } // end namespace llvm
35 
36 STATISTIC(numRegions,       "The # of regions");
37 STATISTIC(numSimpleRegions, "The # of simple regions");
38 
39 // Always verify if expensive checking is enabled.
40 
41 static cl::opt<bool,true>
42 VerifyRegionInfoX(
43   "verify-region-info",
44   cl::location(RegionInfoBase<RegionTraits<Function>>::VerifyRegionInfo),
45   cl::desc("Verify region info (time consuming)"));
46 
47 static cl::opt<Region::PrintStyle, true> printStyleX("print-region-style",
48   cl::location(RegionInfo::printStyle),
49   cl::Hidden,
50   cl::desc("style of printing regions"),
51   cl::values(
52     clEnumValN(Region::PrintNone, "none",  "print no details"),
53     clEnumValN(Region::PrintBB, "bb",
54                "print regions in detail with block_iterator"),
55     clEnumValN(Region::PrintRN, "rn",
56                "print regions in detail with element_iterator")));
57 
58 //===----------------------------------------------------------------------===//
59 // Region implementation
60 //
61 
62 Region::Region(BasicBlock *Entry, BasicBlock *Exit,
63                RegionInfo* RI,
64                DominatorTree *DT, Region *Parent) :
65   RegionBase<RegionTraits<Function>>(Entry, Exit, RI, DT, Parent) {
66 
67 }
68 
69 Region::~Region() = default;
70 
71 //===----------------------------------------------------------------------===//
72 // RegionInfo implementation
73 //
74 
75 RegionInfo::RegionInfo() = default;
76 
77 RegionInfo::~RegionInfo() = default;
78 
79 bool RegionInfo::invalidate(Function &F, const PreservedAnalyses &PA,
80                             FunctionAnalysisManager::Invalidator &) {
81   // Check whether the analysis, all analyses on functions, or the function's
82   // CFG has been preserved.
83   auto PAC = PA.getChecker<RegionInfoAnalysis>();
84   return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
85            PAC.preservedSet<CFGAnalyses>());
86 }
87 
88 void RegionInfo::updateStatistics(Region *R) {
89   ++numRegions;
90 
91   // TODO: Slow. Should only be enabled if -stats is used.
92   if (R->isSimple())
93     ++numSimpleRegions;
94 }
95 
96 void RegionInfo::recalculate(Function &F, DominatorTree *DT_,
97                              PostDominatorTree *PDT_, DominanceFrontier *DF_) {
98   DT = DT_;
99   PDT = PDT_;
100   DF = DF_;
101 
102   TopLevelRegion = new Region(&F.getEntryBlock(), nullptr,
103                               this, DT, nullptr);
104   updateStatistics(TopLevelRegion);
105   calculate(F);
106 }
107 
108 #ifndef NDEBUG
109 void RegionInfo::view() { viewRegion(this); }
110 
111 void RegionInfo::viewOnly() { viewRegionOnly(this); }
112 #endif
113 
114 //===----------------------------------------------------------------------===//
115 // RegionInfoPass implementation
116 //
117 
118 RegionInfoPass::RegionInfoPass() : FunctionPass(ID) {
119   initializeRegionInfoPassPass(*PassRegistry::getPassRegistry());
120 }
121 
122 RegionInfoPass::~RegionInfoPass() = default;
123 
124 bool RegionInfoPass::runOnFunction(Function &F) {
125   releaseMemory();
126 
127   auto DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
128   auto PDT = &getAnalysis<PostDominatorTreeWrapperPass>().getPostDomTree();
129   auto DF = &getAnalysis<DominanceFrontierWrapperPass>().getDominanceFrontier();
130 
131   RI.recalculate(F, DT, PDT, DF);
132   return false;
133 }
134 
135 void RegionInfoPass::releaseMemory() {
136   RI.releaseMemory();
137 }
138 
139 void RegionInfoPass::verifyAnalysis() const {
140     RI.verifyAnalysis();
141 }
142 
143 void RegionInfoPass::getAnalysisUsage(AnalysisUsage &AU) const {
144   AU.setPreservesAll();
145   AU.addRequiredTransitive<DominatorTreeWrapperPass>();
146   AU.addRequired<PostDominatorTreeWrapperPass>();
147   AU.addRequired<DominanceFrontierWrapperPass>();
148 }
149 
150 void RegionInfoPass::print(raw_ostream &OS, const Module *) const {
151   RI.print(OS);
152 }
153 
154 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
155 LLVM_DUMP_METHOD void RegionInfoPass::dump() const {
156   RI.dump();
157 }
158 #endif
159 
160 char RegionInfoPass::ID = 0;
161 
162 INITIALIZE_PASS_BEGIN(RegionInfoPass, "regions",
163                 "Detect single entry single exit regions", true, true)
164 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
165 INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
166 INITIALIZE_PASS_DEPENDENCY(DominanceFrontierWrapperPass)
167 INITIALIZE_PASS_END(RegionInfoPass, "regions",
168                 "Detect single entry single exit regions", true, true)
169 
170 // Create methods available outside of this file, to use them
171 // "include/llvm/LinkAllPasses.h". Otherwise the pass would be deleted by
172 // the link time optimization.
173 
174 namespace llvm {
175 
176   FunctionPass *createRegionInfoPass() {
177     return new RegionInfoPass();
178   }
179 
180 } // end namespace llvm
181 
182 //===----------------------------------------------------------------------===//
183 // RegionInfoAnalysis implementation
184 //
185 
186 AnalysisKey RegionInfoAnalysis::Key;
187 
188 RegionInfo RegionInfoAnalysis::run(Function &F, FunctionAnalysisManager &AM) {
189   RegionInfo RI;
190   auto *DT = &AM.getResult<DominatorTreeAnalysis>(F);
191   auto *PDT = &AM.getResult<PostDominatorTreeAnalysis>(F);
192   auto *DF = &AM.getResult<DominanceFrontierAnalysis>(F);
193 
194   RI.recalculate(F, DT, PDT, DF);
195   return RI;
196 }
197 
198 RegionInfoPrinterPass::RegionInfoPrinterPass(raw_ostream &OS)
199   : OS(OS) {}
200 
201 PreservedAnalyses RegionInfoPrinterPass::run(Function &F,
202                                              FunctionAnalysisManager &AM) {
203   OS << "Region Tree for function: " << F.getName() << "\n";
204   AM.getResult<RegionInfoAnalysis>(F).print(OS);
205 
206   return PreservedAnalyses::all();
207 }
208 
209 PreservedAnalyses RegionInfoVerifierPass::run(Function &F,
210                                               FunctionAnalysisManager &AM) {
211   AM.getResult<RegionInfoAnalysis>(F).verifyAnalysis();
212 
213   return PreservedAnalyses::all();
214 }
215