1 //===- LoopExtractor.cpp - Extract each loop into a new function ----------===//
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 // A pass wrapper around the ExtractLoop() scalar transformation to extract each
11 // top-level loop into its own new function. If the loop is the ONLY loop in a
12 // given function, it is not touched. This is a pass most useful for debugging
13 // via bugpoint.
14 //
15 //===----------------------------------------------------------------------===//
16
17 #define DEBUG_TYPE "loop-extract"
18 #include "llvm/Transforms/IPO.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Module.h"
21 #include "llvm/Pass.h"
22 #include "llvm/Analysis/Dominators.h"
23 #include "llvm/Analysis/LoopPass.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Transforms/Scalar.h"
26 #include "llvm/Transforms/Utils/FunctionUtils.h"
27 #include "llvm/ADT/Statistic.h"
28 #include <fstream>
29 #include <set>
30 using namespace llvm;
31
32 STATISTIC(NumExtracted, "Number of loops extracted");
33
34 namespace {
35 struct LoopExtractor : public LoopPass {
36 static char ID; // Pass identification, replacement for typeid
37 unsigned NumLoops;
38
LoopExtractor__anonaa40b1270111::LoopExtractor39 explicit LoopExtractor(unsigned numLoops = ~0)
40 : LoopPass(ID), NumLoops(numLoops) {}
41
42 virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
43
getAnalysisUsage__anonaa40b1270111::LoopExtractor44 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
45 AU.addRequiredID(BreakCriticalEdgesID);
46 AU.addRequiredID(LoopSimplifyID);
47 AU.addRequired<DominatorTree>();
48 }
49 };
50 }
51
52 char LoopExtractor::ID = 0;
53 INITIALIZE_PASS(LoopExtractor, "loop-extract",
54 "Extract loops into new functions", false, false);
55
56 namespace {
57 /// SingleLoopExtractor - For bugpoint.
58 struct SingleLoopExtractor : public LoopExtractor {
59 static char ID; // Pass identification, replacement for typeid
SingleLoopExtractor__anonaa40b1270211::SingleLoopExtractor60 SingleLoopExtractor() : LoopExtractor(1) {}
61 };
62 } // End anonymous namespace
63
64 char SingleLoopExtractor::ID = 0;
65 INITIALIZE_PASS(SingleLoopExtractor, "loop-extract-single",
66 "Extract at most one loop into a new function", false, false);
67
68 // createLoopExtractorPass - This pass extracts all natural loops from the
69 // program into a function if it can.
70 //
createLoopExtractorPass()71 Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); }
72
runOnLoop(Loop * L,LPPassManager & LPM)73 bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) {
74 // Only visit top-level loops.
75 if (L->getParentLoop())
76 return false;
77
78 // If LoopSimplify form is not available, stay out of trouble.
79 if (!L->isLoopSimplifyForm())
80 return false;
81
82 DominatorTree &DT = getAnalysis<DominatorTree>();
83 bool Changed = false;
84
85 // If there is more than one top-level loop in this function, extract all of
86 // the loops. Otherwise there is exactly one top-level loop; in this case if
87 // this function is more than a minimal wrapper around the loop, extract
88 // the loop.
89 bool ShouldExtractLoop = false;
90
91 // Extract the loop if the entry block doesn't branch to the loop header.
92 TerminatorInst *EntryTI =
93 L->getHeader()->getParent()->getEntryBlock().getTerminator();
94 if (!isa<BranchInst>(EntryTI) ||
95 !cast<BranchInst>(EntryTI)->isUnconditional() ||
96 EntryTI->getSuccessor(0) != L->getHeader())
97 ShouldExtractLoop = true;
98 else {
99 // Check to see if any exits from the loop are more than just return
100 // blocks.
101 SmallVector<BasicBlock*, 8> ExitBlocks;
102 L->getExitBlocks(ExitBlocks);
103 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
104 if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) {
105 ShouldExtractLoop = true;
106 break;
107 }
108 }
109 if (ShouldExtractLoop) {
110 if (NumLoops == 0) return Changed;
111 --NumLoops;
112 if (ExtractLoop(DT, L) != 0) {
113 Changed = true;
114 // After extraction, the loop is replaced by a function call, so
115 // we shouldn't try to run any more loop passes on it.
116 LPM.deleteLoopFromQueue(L);
117 }
118 ++NumExtracted;
119 }
120
121 return Changed;
122 }
123
124 // createSingleLoopExtractorPass - This pass extracts one natural loop from the
125 // program into a function if it can. This is used by bugpoint.
126 //
createSingleLoopExtractorPass()127 Pass *llvm::createSingleLoopExtractorPass() {
128 return new SingleLoopExtractor();
129 }
130
131
132 // BlockFile - A file which contains a list of blocks that should not be
133 // extracted.
134 static cl::opt<std::string>
135 BlockFile("extract-blocks-file", cl::value_desc("filename"),
136 cl::desc("A file containing list of basic blocks to not extract"),
137 cl::Hidden);
138
139 namespace {
140 /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks
141 /// from the module into their own functions except for those specified by the
142 /// BlocksToNotExtract list.
143 class BlockExtractorPass : public ModulePass {
144 void LoadFile(const char *Filename);
145
146 std::vector<BasicBlock*> BlocksToNotExtract;
147 std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName;
148 public:
149 static char ID; // Pass identification, replacement for typeid
BlockExtractorPass()150 BlockExtractorPass() : ModulePass(ID) {
151 if (!BlockFile.empty())
152 LoadFile(BlockFile.c_str());
153 }
154
155 bool runOnModule(Module &M);
156 };
157 }
158
159 char BlockExtractorPass::ID = 0;
160 INITIALIZE_PASS(BlockExtractorPass, "extract-blocks",
161 "Extract Basic Blocks From Module (for bugpoint use)",
162 false, false);
163
164 // createBlockExtractorPass - This pass extracts all blocks (except those
165 // specified in the argument list) from the functions in the module.
166 //
createBlockExtractorPass()167 ModulePass *llvm::createBlockExtractorPass()
168 {
169 return new BlockExtractorPass();
170 }
171
LoadFile(const char * Filename)172 void BlockExtractorPass::LoadFile(const char *Filename) {
173 // Load the BlockFile...
174 std::ifstream In(Filename);
175 if (!In.good()) {
176 errs() << "WARNING: BlockExtractor couldn't load file '" << Filename
177 << "'!\n";
178 return;
179 }
180 while (In) {
181 std::string FunctionName, BlockName;
182 In >> FunctionName;
183 In >> BlockName;
184 if (!BlockName.empty())
185 BlocksToNotExtractByName.push_back(
186 std::make_pair(FunctionName, BlockName));
187 }
188 }
189
runOnModule(Module & M)190 bool BlockExtractorPass::runOnModule(Module &M) {
191 std::set<BasicBlock*> TranslatedBlocksToNotExtract;
192 for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) {
193 BasicBlock *BB = BlocksToNotExtract[i];
194 Function *F = BB->getParent();
195
196 // Map the corresponding function in this module.
197 Function *MF = M.getFunction(F->getName());
198 assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?");
199
200 // Figure out which index the basic block is in its function.
201 Function::iterator BBI = MF->begin();
202 std::advance(BBI, std::distance(F->begin(), Function::iterator(BB)));
203 TranslatedBlocksToNotExtract.insert(BBI);
204 }
205
206 while (!BlocksToNotExtractByName.empty()) {
207 // There's no way to find BBs by name without looking at every BB inside
208 // every Function. Fortunately, this is always empty except when used by
209 // bugpoint in which case correctness is more important than performance.
210
211 std::string &FuncName = BlocksToNotExtractByName.back().first;
212 std::string &BlockName = BlocksToNotExtractByName.back().second;
213
214 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
215 Function &F = *FI;
216 if (F.getName() != FuncName) continue;
217
218 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
219 BasicBlock &BB = *BI;
220 if (BB.getName() != BlockName) continue;
221
222 TranslatedBlocksToNotExtract.insert(BI);
223 }
224 }
225
226 BlocksToNotExtractByName.pop_back();
227 }
228
229 // Now that we know which blocks to not extract, figure out which ones we WANT
230 // to extract.
231 std::vector<BasicBlock*> BlocksToExtract;
232 for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
233 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
234 if (!TranslatedBlocksToNotExtract.count(BB))
235 BlocksToExtract.push_back(BB);
236
237 for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i)
238 ExtractBasicBlock(BlocksToExtract[i]);
239
240 return !BlocksToExtract.empty();
241 }
242