1 //===- LoopExtractor.cpp - Extract each loop into a new function ----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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
15 //===----------------------------------------------------------------------===//
17 #include "llvm/Transforms/IPO.h"
18 #include "llvm/ADT/Statistic.h"
19 #include "llvm/Analysis/LoopPass.h"
20 #include "llvm/IR/Dominators.h"
21 #include "llvm/IR/Instructions.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/Pass.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Transforms/Scalar.h"
26 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
27 #include "llvm/Transforms/Utils/CodeExtractor.h"
32 #define DEBUG_TYPE "loop-extract"
34 STATISTIC(NumExtracted, "Number of loops extracted");
37 struct LoopExtractor : public LoopPass {
38 static char ID; // Pass identification, replacement for typeid
41 explicit LoopExtractor(unsigned numLoops = ~0)
42 : LoopPass(ID), NumLoops(numLoops) {
43 initializeLoopExtractorPass(*PassRegistry::getPassRegistry());
46 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
48 void getAnalysisUsage(AnalysisUsage &AU) const override {
49 AU.addRequiredID(BreakCriticalEdgesID);
50 AU.addRequiredID(LoopSimplifyID);
51 AU.addRequired<DominatorTreeWrapperPass>();
56 char LoopExtractor::ID = 0;
57 INITIALIZE_PASS_BEGIN(LoopExtractor, "loop-extract",
58 "Extract loops into new functions", false, false)
59 INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges)
60 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
61 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
62 INITIALIZE_PASS_END(LoopExtractor, "loop-extract",
63 "Extract loops into new functions", false, false)
66 /// SingleLoopExtractor - For bugpoint.
67 struct SingleLoopExtractor : public LoopExtractor {
68 static char ID; // Pass identification, replacement for typeid
69 SingleLoopExtractor() : LoopExtractor(1) {}
71 } // End anonymous namespace
73 char SingleLoopExtractor::ID = 0;
74 INITIALIZE_PASS(SingleLoopExtractor, "loop-extract-single",
75 "Extract at most one loop into a new function", false, false)
77 // createLoopExtractorPass - This pass extracts all natural loops from the
78 // program into a function if it can.
80 Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); }
82 bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) {
83 if (skipOptnoneFunction(L))
86 // Only visit top-level loops.
87 if (L->getParentLoop())
90 // If LoopSimplify form is not available, stay out of trouble.
91 if (!L->isLoopSimplifyForm())
94 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
97 // If there is more than one top-level loop in this function, extract all of
98 // the loops. Otherwise there is exactly one top-level loop; in this case if
99 // this function is more than a minimal wrapper around the loop, extract
101 bool ShouldExtractLoop = false;
103 // Extract the loop if the entry block doesn't branch to the loop header.
104 TerminatorInst *EntryTI =
105 L->getHeader()->getParent()->getEntryBlock().getTerminator();
106 if (!isa<BranchInst>(EntryTI) ||
107 !cast<BranchInst>(EntryTI)->isUnconditional() ||
108 EntryTI->getSuccessor(0) != L->getHeader()) {
109 ShouldExtractLoop = true;
111 // Check to see if any exits from the loop are more than just return
113 SmallVector<BasicBlock*, 8> ExitBlocks;
114 L->getExitBlocks(ExitBlocks);
115 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
116 if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) {
117 ShouldExtractLoop = true;
122 if (ShouldExtractLoop) {
123 // We must omit landing pads. Landing pads must accompany the invoke
124 // instruction. But this would result in a loop in the extracted
125 // function. An infinite cycle occurs when it tries to extract that loop as
127 SmallVector<BasicBlock*, 8> ExitBlocks;
128 L->getExitBlocks(ExitBlocks);
129 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
130 if (ExitBlocks[i]->isLandingPad()) {
131 ShouldExtractLoop = false;
136 if (ShouldExtractLoop) {
137 if (NumLoops == 0) return Changed;
139 CodeExtractor Extractor(DT, *L);
140 if (Extractor.extractCodeRegion() != nullptr) {
142 // After extraction, the loop is replaced by a function call, so
143 // we shouldn't try to run any more loop passes on it.
144 LPM.deleteLoopFromQueue(L);
152 // createSingleLoopExtractorPass - This pass extracts one natural loop from the
153 // program into a function if it can. This is used by bugpoint.
155 Pass *llvm::createSingleLoopExtractorPass() {
156 return new SingleLoopExtractor();
160 // BlockFile - A file which contains a list of blocks that should not be
162 static cl::opt<std::string>
163 BlockFile("extract-blocks-file", cl::value_desc("filename"),
164 cl::desc("A file containing list of basic blocks to not extract"),
168 /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks
169 /// from the module into their own functions except for those specified by the
170 /// BlocksToNotExtract list.
171 class BlockExtractorPass : public ModulePass {
172 void LoadFile(const char *Filename);
173 void SplitLandingPadPreds(Function *F);
175 std::vector<BasicBlock*> BlocksToNotExtract;
176 std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName;
178 static char ID; // Pass identification, replacement for typeid
179 BlockExtractorPass() : ModulePass(ID) {
180 if (!BlockFile.empty())
181 LoadFile(BlockFile.c_str());
184 bool runOnModule(Module &M) override;
188 char BlockExtractorPass::ID = 0;
189 INITIALIZE_PASS(BlockExtractorPass, "extract-blocks",
190 "Extract Basic Blocks From Module (for bugpoint use)",
193 // createBlockExtractorPass - This pass extracts all blocks (except those
194 // specified in the argument list) from the functions in the module.
196 ModulePass *llvm::createBlockExtractorPass() {
197 return new BlockExtractorPass();
200 void BlockExtractorPass::LoadFile(const char *Filename) {
201 // Load the BlockFile...
202 std::ifstream In(Filename);
204 errs() << "WARNING: BlockExtractor couldn't load file '" << Filename
209 std::string FunctionName, BlockName;
212 if (!BlockName.empty())
213 BlocksToNotExtractByName.push_back(
214 std::make_pair(FunctionName, BlockName));
218 /// SplitLandingPadPreds - The landing pad needs to be extracted with the invoke
219 /// instruction. The critical edge breaker will refuse to break critical edges
220 /// to a landing pad. So do them here. After this method runs, all landing pads
221 /// should have only one predecessor.
222 void BlockExtractorPass::SplitLandingPadPreds(Function *F) {
223 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
224 InvokeInst *II = dyn_cast<InvokeInst>(I);
226 BasicBlock *Parent = II->getParent();
227 BasicBlock *LPad = II->getUnwindDest();
229 // Look through the landing pad's predecessors. If one of them ends in an
230 // 'invoke', then we want to split the landing pad.
233 PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ++PI) {
234 BasicBlock *BB = *PI;
235 if (BB->isLandingPad() && BB != Parent &&
236 isa<InvokeInst>(Parent->getTerminator())) {
242 if (!Split) continue;
244 SmallVector<BasicBlock*, 2> NewBBs;
245 SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", NewBBs);
249 bool BlockExtractorPass::runOnModule(Module &M) {
250 std::set<BasicBlock*> TranslatedBlocksToNotExtract;
251 for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) {
252 BasicBlock *BB = BlocksToNotExtract[i];
253 Function *F = BB->getParent();
255 // Map the corresponding function in this module.
256 Function *MF = M.getFunction(F->getName());
257 assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?");
259 // Figure out which index the basic block is in its function.
260 Function::iterator BBI = MF->begin();
261 std::advance(BBI, std::distance(F->begin(), Function::iterator(BB)));
262 TranslatedBlocksToNotExtract.insert(BBI);
265 while (!BlocksToNotExtractByName.empty()) {
266 // There's no way to find BBs by name without looking at every BB inside
267 // every Function. Fortunately, this is always empty except when used by
268 // bugpoint in which case correctness is more important than performance.
270 std::string &FuncName = BlocksToNotExtractByName.back().first;
271 std::string &BlockName = BlocksToNotExtractByName.back().second;
273 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
275 if (F.getName() != FuncName) continue;
277 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
278 BasicBlock &BB = *BI;
279 if (BB.getName() != BlockName) continue;
281 TranslatedBlocksToNotExtract.insert(BI);
285 BlocksToNotExtractByName.pop_back();
288 // Now that we know which blocks to not extract, figure out which ones we WANT
290 std::vector<BasicBlock*> BlocksToExtract;
291 for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
292 SplitLandingPadPreds(&*F);
293 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
294 if (!TranslatedBlocksToNotExtract.count(BB))
295 BlocksToExtract.push_back(BB);
298 for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i) {
299 SmallVector<BasicBlock*, 2> BlocksToExtractVec;
300 BlocksToExtractVec.push_back(BlocksToExtract[i]);
301 if (const InvokeInst *II =
302 dyn_cast<InvokeInst>(BlocksToExtract[i]->getTerminator()))
303 BlocksToExtractVec.push_back(II->getUnwindDest());
304 CodeExtractor(BlocksToExtractVec).extractCodeRegion();
307 return !BlocksToExtract.empty();