1 //===- ExtractFunction.cpp - Extract a function from Program --------------===//
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 implements several methods that are used to extract functions,
11 // loops, or portions of a module from the rest of the module.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "BugDriver.h"
16 #include "llvm/Constants.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/LLVMContext.h"
19 #include "llvm/Module.h"
20 #include "llvm/PassManager.h"
21 #include "llvm/Pass.h"
22 #include "llvm/Analysis/Verifier.h"
23 #include "llvm/Assembly/Writer.h"
24 #include "llvm/Transforms/IPO.h"
25 #include "llvm/Transforms/Scalar.h"
26 #include "llvm/Transforms/Utils/Cloning.h"
27 #include "llvm/Transforms/Utils/FunctionUtils.h"
28 #include "llvm/Target/TargetData.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/FileUtilities.h"
32 #include "llvm/Support/ToolOutputFile.h"
33 #include "llvm/Support/Path.h"
34 #include "llvm/Support/Signals.h"
35 #include <set>
36 using namespace llvm;
37
38 namespace llvm {
39 bool DisableSimplifyCFG = false;
40 extern cl::opt<std::string> OutputPrefix;
41 } // End llvm namespace
42
43 namespace {
44 cl::opt<bool>
45 NoDCE ("disable-dce",
46 cl::desc("Do not use the -dce pass to reduce testcases"));
47 cl::opt<bool, true>
48 NoSCFG("disable-simplifycfg", cl::location(DisableSimplifyCFG),
49 cl::desc("Do not use the -simplifycfg pass to reduce testcases"));
50
globalInitUsesExternalBA(GlobalVariable * GV)51 Function* globalInitUsesExternalBA(GlobalVariable* GV) {
52 if (!GV->hasInitializer())
53 return 0;
54
55 Constant *I = GV->getInitializer();
56
57 // walk the values used by the initializer
58 // (and recurse into things like ConstantExpr)
59 std::vector<Constant*> Todo;
60 std::set<Constant*> Done;
61 Todo.push_back(I);
62
63 while (!Todo.empty()) {
64 Constant* V = Todo.back();
65 Todo.pop_back();
66 Done.insert(V);
67
68 if (BlockAddress *BA = dyn_cast<BlockAddress>(V)) {
69 Function *F = BA->getFunction();
70 if (F->isDeclaration())
71 return F;
72 }
73
74 for (User::op_iterator i = V->op_begin(), e = V->op_end(); i != e; ++i) {
75 Constant *C = dyn_cast<Constant>(*i);
76 if (C && !isa<GlobalValue>(C) && !Done.count(C))
77 Todo.push_back(C);
78 }
79 }
80 return 0;
81 }
82 } // end anonymous namespace
83
84 /// deleteInstructionFromProgram - This method clones the current Program and
85 /// deletes the specified instruction from the cloned module. It then runs a
86 /// series of cleanup passes (ADCE and SimplifyCFG) to eliminate any code which
87 /// depends on the value. The modified module is then returned.
88 ///
deleteInstructionFromProgram(const Instruction * I,unsigned Simplification)89 Module *BugDriver::deleteInstructionFromProgram(const Instruction *I,
90 unsigned Simplification) {
91 // FIXME, use vmap?
92 Module *Clone = CloneModule(Program);
93
94 const BasicBlock *PBB = I->getParent();
95 const Function *PF = PBB->getParent();
96
97 Module::iterator RFI = Clone->begin(); // Get iterator to corresponding fn
98 std::advance(RFI, std::distance(PF->getParent()->begin(),
99 Module::const_iterator(PF)));
100
101 Function::iterator RBI = RFI->begin(); // Get iterator to corresponding BB
102 std::advance(RBI, std::distance(PF->begin(), Function::const_iterator(PBB)));
103
104 BasicBlock::iterator RI = RBI->begin(); // Get iterator to corresponding inst
105 std::advance(RI, std::distance(PBB->begin(), BasicBlock::const_iterator(I)));
106 Instruction *TheInst = RI; // Got the corresponding instruction!
107
108 // If this instruction produces a value, replace any users with null values
109 if (!TheInst->getType()->isVoidTy())
110 TheInst->replaceAllUsesWith(Constant::getNullValue(TheInst->getType()));
111
112 // Remove the instruction from the program.
113 TheInst->getParent()->getInstList().erase(TheInst);
114
115 // Spiff up the output a little bit.
116 std::vector<std::string> Passes;
117
118 /// Can we get rid of the -disable-* options?
119 if (Simplification > 1 && !NoDCE)
120 Passes.push_back("dce");
121 if (Simplification && !DisableSimplifyCFG)
122 Passes.push_back("simplifycfg"); // Delete dead control flow
123
124 Passes.push_back("verify");
125 Module *New = runPassesOn(Clone, Passes);
126 delete Clone;
127 if (!New) {
128 errs() << "Instruction removal failed. Sorry. :( Please report a bug!\n";
129 exit(1);
130 }
131 return New;
132 }
133
134 /// performFinalCleanups - This method clones the current Program and performs
135 /// a series of cleanups intended to get rid of extra cruft on the module
136 /// before handing it to the user.
137 ///
performFinalCleanups(Module * M,bool MayModifySemantics)138 Module *BugDriver::performFinalCleanups(Module *M, bool MayModifySemantics) {
139 // Make all functions external, so GlobalDCE doesn't delete them...
140 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
141 I->setLinkage(GlobalValue::ExternalLinkage);
142
143 std::vector<std::string> CleanupPasses;
144 CleanupPasses.push_back("globaldce");
145
146 if (MayModifySemantics)
147 CleanupPasses.push_back("deadarghaX0r");
148 else
149 CleanupPasses.push_back("deadargelim");
150
151 Module *New = runPassesOn(M, CleanupPasses);
152 if (New == 0) {
153 errs() << "Final cleanups failed. Sorry. :( Please report a bug!\n";
154 return M;
155 }
156 delete M;
157 return New;
158 }
159
160
161 /// ExtractLoop - Given a module, extract up to one loop from it into a new
162 /// function. This returns null if there are no extractable loops in the
163 /// program or if the loop extractor crashes.
ExtractLoop(Module * M)164 Module *BugDriver::ExtractLoop(Module *M) {
165 std::vector<std::string> LoopExtractPasses;
166 LoopExtractPasses.push_back("loop-extract-single");
167
168 Module *NewM = runPassesOn(M, LoopExtractPasses);
169 if (NewM == 0) {
170 outs() << "*** Loop extraction failed: ";
171 EmitProgressBitcode(M, "loopextraction", true);
172 outs() << "*** Sorry. :( Please report a bug!\n";
173 return 0;
174 }
175
176 // Check to see if we created any new functions. If not, no loops were
177 // extracted and we should return null. Limit the number of loops we extract
178 // to avoid taking forever.
179 static unsigned NumExtracted = 32;
180 if (M->size() == NewM->size() || --NumExtracted == 0) {
181 delete NewM;
182 return 0;
183 } else {
184 assert(M->size() < NewM->size() && "Loop extract removed functions?");
185 Module::iterator MI = NewM->begin();
186 for (unsigned i = 0, e = M->size(); i != e; ++i)
187 ++MI;
188 }
189
190 return NewM;
191 }
192
193
194 // DeleteFunctionBody - "Remove" the function by deleting all of its basic
195 // blocks, making it external.
196 //
DeleteFunctionBody(Function * F)197 void llvm::DeleteFunctionBody(Function *F) {
198 // delete the body of the function...
199 F->deleteBody();
200 assert(F->isDeclaration() && "This didn't make the function external!");
201 }
202
203 /// GetTorInit - Given a list of entries for static ctors/dtors, return them
204 /// as a constant array.
GetTorInit(std::vector<std::pair<Function *,int>> & TorList)205 static Constant *GetTorInit(std::vector<std::pair<Function*, int> > &TorList) {
206 assert(!TorList.empty() && "Don't create empty tor list!");
207 std::vector<Constant*> ArrayElts;
208 Type *Int32Ty = Type::getInt32Ty(TorList[0].first->getContext());
209
210 StructType *STy =
211 StructType::get(Int32Ty, TorList[0].first->getType(), NULL);
212 for (unsigned i = 0, e = TorList.size(); i != e; ++i) {
213 Constant *Elts[] = {
214 ConstantInt::get(Int32Ty, TorList[i].second),
215 TorList[i].first
216 };
217 ArrayElts.push_back(ConstantStruct::get(STy, Elts));
218 }
219 return ConstantArray::get(ArrayType::get(ArrayElts[0]->getType(),
220 ArrayElts.size()),
221 ArrayElts);
222 }
223
224 /// SplitStaticCtorDtor - A module was recently split into two parts, M1/M2, and
225 /// M1 has all of the global variables. If M2 contains any functions that are
226 /// static ctors/dtors, we need to add an llvm.global_[cd]tors global to M2, and
227 /// prune appropriate entries out of M1s list.
SplitStaticCtorDtor(const char * GlobalName,Module * M1,Module * M2,ValueToValueMapTy & VMap)228 static void SplitStaticCtorDtor(const char *GlobalName, Module *M1, Module *M2,
229 ValueToValueMapTy &VMap) {
230 GlobalVariable *GV = M1->getNamedGlobal(GlobalName);
231 if (!GV || GV->isDeclaration() || GV->hasLocalLinkage() ||
232 !GV->use_empty()) return;
233
234 std::vector<std::pair<Function*, int> > M1Tors, M2Tors;
235 ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
236 if (!InitList) return;
237
238 for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
239 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
240 if (CS->getNumOperands() != 2) return; // Not array of 2-element structs.
241
242 if (CS->getOperand(1)->isNullValue())
243 break; // Found a null terminator, stop here.
244
245 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0));
246 int Priority = CI ? CI->getSExtValue() : 0;
247
248 Constant *FP = CS->getOperand(1);
249 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
250 if (CE->isCast())
251 FP = CE->getOperand(0);
252 if (Function *F = dyn_cast<Function>(FP)) {
253 if (!F->isDeclaration())
254 M1Tors.push_back(std::make_pair(F, Priority));
255 else {
256 // Map to M2's version of the function.
257 F = cast<Function>(VMap[F]);
258 M2Tors.push_back(std::make_pair(F, Priority));
259 }
260 }
261 }
262 }
263
264 GV->eraseFromParent();
265 if (!M1Tors.empty()) {
266 Constant *M1Init = GetTorInit(M1Tors);
267 new GlobalVariable(*M1, M1Init->getType(), false,
268 GlobalValue::AppendingLinkage,
269 M1Init, GlobalName);
270 }
271
272 GV = M2->getNamedGlobal(GlobalName);
273 assert(GV && "Not a clone of M1?");
274 assert(GV->use_empty() && "llvm.ctors shouldn't have uses!");
275
276 GV->eraseFromParent();
277 if (!M2Tors.empty()) {
278 Constant *M2Init = GetTorInit(M2Tors);
279 new GlobalVariable(*M2, M2Init->getType(), false,
280 GlobalValue::AppendingLinkage,
281 M2Init, GlobalName);
282 }
283 }
284
285
286 /// SplitFunctionsOutOfModule - Given a module and a list of functions in the
287 /// module, split the functions OUT of the specified module, and place them in
288 /// the new module.
289 Module *
SplitFunctionsOutOfModule(Module * M,const std::vector<Function * > & F,ValueToValueMapTy & VMap)290 llvm::SplitFunctionsOutOfModule(Module *M,
291 const std::vector<Function*> &F,
292 ValueToValueMapTy &VMap) {
293 // Make sure functions & globals are all external so that linkage
294 // between the two modules will work.
295 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
296 I->setLinkage(GlobalValue::ExternalLinkage);
297 for (Module::global_iterator I = M->global_begin(), E = M->global_end();
298 I != E; ++I) {
299 if (I->hasName() && I->getName()[0] == '\01')
300 I->setName(I->getName().substr(1));
301 I->setLinkage(GlobalValue::ExternalLinkage);
302 }
303
304 ValueToValueMapTy NewVMap;
305 Module *New = CloneModule(M, NewVMap);
306
307 // Remove the Test functions from the Safe module
308 std::set<Function *> TestFunctions;
309 for (unsigned i = 0, e = F.size(); i != e; ++i) {
310 Function *TNOF = cast<Function>(VMap[F[i]]);
311 DEBUG(errs() << "Removing function ");
312 DEBUG(WriteAsOperand(errs(), TNOF, false));
313 DEBUG(errs() << "\n");
314 TestFunctions.insert(cast<Function>(NewVMap[TNOF]));
315 DeleteFunctionBody(TNOF); // Function is now external in this module!
316 }
317
318
319 // Remove the Safe functions from the Test module
320 for (Module::iterator I = New->begin(), E = New->end(); I != E; ++I)
321 if (!TestFunctions.count(I))
322 DeleteFunctionBody(I);
323
324
325 // Try to split the global initializers evenly
326 for (Module::global_iterator I = M->global_begin(), E = M->global_end();
327 I != E; ++I) {
328 GlobalVariable *GV = cast<GlobalVariable>(NewVMap[I]);
329 if (Function *TestFn = globalInitUsesExternalBA(I)) {
330 if (Function *SafeFn = globalInitUsesExternalBA(GV)) {
331 errs() << "*** Error: when reducing functions, encountered "
332 "the global '";
333 WriteAsOperand(errs(), GV, false);
334 errs() << "' with an initializer that references blockaddresses "
335 "from safe function '" << SafeFn->getName()
336 << "' and from test function '" << TestFn->getName() << "'.\n";
337 exit(1);
338 }
339 I->setInitializer(0); // Delete the initializer to make it external
340 } else {
341 // If we keep it in the safe module, then delete it in the test module
342 GV->setInitializer(0);
343 }
344 }
345
346 // Make sure that there is a global ctor/dtor array in both halves of the
347 // module if they both have static ctor/dtor functions.
348 SplitStaticCtorDtor("llvm.global_ctors", M, New, NewVMap);
349 SplitStaticCtorDtor("llvm.global_dtors", M, New, NewVMap);
350
351 return New;
352 }
353
354 //===----------------------------------------------------------------------===//
355 // Basic Block Extraction Code
356 //===----------------------------------------------------------------------===//
357
358 /// ExtractMappedBlocksFromModule - Extract all but the specified basic blocks
359 /// into their own functions. The only detail is that M is actually a module
360 /// cloned from the one the BBs are in, so some mapping needs to be performed.
361 /// If this operation fails for some reason (ie the implementation is buggy),
362 /// this function should return null, otherwise it returns a new Module.
ExtractMappedBlocksFromModule(const std::vector<BasicBlock * > & BBs,Module * M)363 Module *BugDriver::ExtractMappedBlocksFromModule(const
364 std::vector<BasicBlock*> &BBs,
365 Module *M) {
366 sys::Path uniqueFilename(OutputPrefix + "-extractblocks");
367 std::string ErrMsg;
368 if (uniqueFilename.createTemporaryFileOnDisk(true, &ErrMsg)) {
369 outs() << "*** Basic Block extraction failed!\n";
370 errs() << "Error creating temporary file: " << ErrMsg << "\n";
371 EmitProgressBitcode(M, "basicblockextractfail", true);
372 return 0;
373 }
374 sys::RemoveFileOnSignal(uniqueFilename);
375
376 std::string ErrorInfo;
377 tool_output_file BlocksToNotExtractFile(uniqueFilename.c_str(), ErrorInfo);
378 if (!ErrorInfo.empty()) {
379 outs() << "*** Basic Block extraction failed!\n";
380 errs() << "Error writing list of blocks to not extract: " << ErrorInfo
381 << "\n";
382 EmitProgressBitcode(M, "basicblockextractfail", true);
383 return 0;
384 }
385 for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
386 I != E; ++I) {
387 BasicBlock *BB = *I;
388 // If the BB doesn't have a name, give it one so we have something to key
389 // off of.
390 if (!BB->hasName()) BB->setName("tmpbb");
391 BlocksToNotExtractFile.os() << BB->getParent()->getName() << " "
392 << BB->getName() << "\n";
393 }
394 BlocksToNotExtractFile.os().close();
395 if (BlocksToNotExtractFile.os().has_error()) {
396 errs() << "Error writing list of blocks to not extract: " << ErrorInfo
397 << "\n";
398 EmitProgressBitcode(M, "basicblockextractfail", true);
399 BlocksToNotExtractFile.os().clear_error();
400 return 0;
401 }
402 BlocksToNotExtractFile.keep();
403
404 std::string uniqueFN = "--extract-blocks-file=" + uniqueFilename.str();
405 const char *ExtraArg = uniqueFN.c_str();
406
407 std::vector<std::string> PI;
408 PI.push_back("extract-blocks");
409 Module *Ret = runPassesOn(M, PI, false, 1, &ExtraArg);
410
411 uniqueFilename.eraseFromDisk(); // Free disk space
412
413 if (Ret == 0) {
414 outs() << "*** Basic Block extraction failed, please report a bug!\n";
415 EmitProgressBitcode(M, "basicblockextractfail", true);
416 }
417 return Ret;
418 }
419