1 //===- CrashDebugger.cpp - Debug compilation crashes ----------------------===//
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 // This file defines the bugpoint internals that narrow down compilation crashes
12 //===----------------------------------------------------------------------===//
14 #include "BugDriver.h"
15 #include "ListReducer.h"
16 #include "ToolRunner.h"
17 #include "llvm/ADT/SmallPtrSet.h"
18 #include "llvm/IR/CFG.h"
19 #include "llvm/IR/Constants.h"
20 #include "llvm/IR/DerivedTypes.h"
21 #include "llvm/IR/Instructions.h"
22 #include "llvm/IR/LegacyPassManager.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/IR/ValueSymbolTable.h"
25 #include "llvm/IR/Verifier.h"
26 #include "llvm/Pass.h"
27 #include "llvm/Support/CommandLine.h"
28 #include "llvm/Support/FileUtilities.h"
29 #include "llvm/Transforms/Scalar.h"
30 #include "llvm/Transforms/Utils/Cloning.h"
37 cl::desc("Force function reduction to keep main"),
40 NoGlobalRM ("disable-global-remove",
41 cl::desc("Do not remove global variables"),
45 ReplaceFuncsWithNull("replace-funcs-with-null",
46 cl::desc("When stubbing functions, replace all uses will null"),
49 DontReducePassList("disable-pass-list-reduction",
50 cl::desc("Skip pass list reduction steps"),
55 class ReducePassList : public ListReducer<std::string> {
58 ReducePassList(BugDriver &bd) : BD(bd) {}
60 // doTest - Return true iff running the "removed" passes succeeds, and
61 // running the "Kept" passes fail when run on the output of the "removed"
62 // passes. If we return true, we update the current module of bugpoint.
64 TestResult doTest(std::vector<std::string> &Removed,
65 std::vector<std::string> &Kept,
66 std::string &Error) override;
70 ReducePassList::TestResult
71 ReducePassList::doTest(std::vector<std::string> &Prefix,
72 std::vector<std::string> &Suffix,
74 std::string PrefixOutput;
75 Module *OrigProgram = nullptr;
76 if (!Prefix.empty()) {
77 outs() << "Checking to see if these passes crash: "
78 << getPassesString(Prefix) << ": ";
79 if (BD.runPasses(BD.getProgram(), Prefix, PrefixOutput))
82 OrigProgram = BD.Program;
84 BD.Program = parseInputFile(PrefixOutput, BD.getContext()).release();
85 if (BD.Program == nullptr) {
86 errs() << BD.getToolName() << ": Error reading bitcode file '"
87 << PrefixOutput << "'!\n";
90 sys::fs::remove(PrefixOutput);
93 outs() << "Checking to see if these passes crash: "
94 << getPassesString(Suffix) << ": ";
96 if (BD.runPasses(BD.getProgram(), Suffix)) {
97 delete OrigProgram; // The suffix crashes alone...
101 // Nothing failed, restore state...
104 BD.Program = OrigProgram;
110 /// ReduceCrashingGlobalVariables - This works by removing the global
111 /// variable's initializer and seeing if the program still crashes. If it
112 /// does, then we keep that program and try again.
114 class ReduceCrashingGlobalVariables : public ListReducer<GlobalVariable*> {
116 bool (*TestFn)(const BugDriver &, Module *);
118 ReduceCrashingGlobalVariables(BugDriver &bd,
119 bool (*testFn)(const BugDriver &, Module *))
120 : BD(bd), TestFn(testFn) {}
122 TestResult doTest(std::vector<GlobalVariable*> &Prefix,
123 std::vector<GlobalVariable*> &Kept,
124 std::string &Error) override {
125 if (!Kept.empty() && TestGlobalVariables(Kept))
127 if (!Prefix.empty() && TestGlobalVariables(Prefix))
132 bool TestGlobalVariables(std::vector<GlobalVariable*> &GVs);
137 ReduceCrashingGlobalVariables::TestGlobalVariables(
138 std::vector<GlobalVariable*> &GVs) {
139 // Clone the program to try hacking it apart...
140 ValueToValueMapTy VMap;
141 Module *M = CloneModule(BD.getProgram(), VMap);
143 // Convert list to set for fast lookup...
144 std::set<GlobalVariable*> GVSet;
146 for (unsigned i = 0, e = GVs.size(); i != e; ++i) {
147 GlobalVariable* CMGV = cast<GlobalVariable>(VMap[GVs[i]]);
148 assert(CMGV && "Global Variable not in module?!");
152 outs() << "Checking for crash with only these global variables: ";
153 PrintGlobalVariableList(GVs);
156 // Loop over and delete any global variables which we aren't supposed to be
158 for (Module::global_iterator I = M->global_begin(), E = M->global_end();
160 if (I->hasInitializer() && !GVSet.count(I)) {
161 I->setInitializer(nullptr);
162 I->setLinkage(GlobalValue::ExternalLinkage);
165 // Try running the hacked up program...
167 BD.setNewProgram(M); // It crashed, keep the trimmed version...
169 // Make sure to use global variable pointers that point into the now-current
171 GVs.assign(GVSet.begin(), GVSet.end());
180 /// ReduceCrashingFunctions reducer - This works by removing functions and
181 /// seeing if the program still crashes. If it does, then keep the newer,
184 class ReduceCrashingFunctions : public ListReducer<Function*> {
186 bool (*TestFn)(const BugDriver &, Module *);
188 ReduceCrashingFunctions(BugDriver &bd,
189 bool (*testFn)(const BugDriver &, Module *))
190 : BD(bd), TestFn(testFn) {}
192 TestResult doTest(std::vector<Function*> &Prefix,
193 std::vector<Function*> &Kept,
194 std::string &Error) override {
195 if (!Kept.empty() && TestFuncs(Kept))
197 if (!Prefix.empty() && TestFuncs(Prefix))
202 bool TestFuncs(std::vector<Function*> &Prefix);
206 static void RemoveFunctionReferences(Module *M, const char* Name) {
207 auto *UsedVar = M->getGlobalVariable(Name, true);
208 if (!UsedVar || !UsedVar->hasInitializer()) return;
209 if (isa<ConstantAggregateZero>(UsedVar->getInitializer())) {
210 assert(UsedVar->use_empty());
211 UsedVar->eraseFromParent();
214 auto *OldUsedVal = cast<ConstantArray>(UsedVar->getInitializer());
215 std::vector<Constant*> Used;
216 for(Value *V : OldUsedVal->operand_values()) {
217 Constant *Op = cast<Constant>(V->stripPointerCasts());
218 if(!Op->isNullValue()) {
219 Used.push_back(cast<Constant>(V));
222 auto *NewValElemTy = OldUsedVal->getType()->getElementType();
223 auto *NewValTy = ArrayType::get(NewValElemTy, Used.size());
224 auto *NewUsedVal = ConstantArray::get(NewValTy, Used);
225 UsedVar->mutateType(NewUsedVal->getType()->getPointerTo());
226 UsedVar->setInitializer(NewUsedVal);
229 bool ReduceCrashingFunctions::TestFuncs(std::vector<Function*> &Funcs) {
230 // If main isn't present, claim there is no problem.
231 if (KeepMain && std::find(Funcs.begin(), Funcs.end(),
232 BD.getProgram()->getFunction("main")) ==
236 // Clone the program to try hacking it apart...
237 ValueToValueMapTy VMap;
238 Module *M = CloneModule(BD.getProgram(), VMap);
240 // Convert list to set for fast lookup...
241 std::set<Function*> Functions;
242 for (unsigned i = 0, e = Funcs.size(); i != e; ++i) {
243 Function *CMF = cast<Function>(VMap[Funcs[i]]);
244 assert(CMF && "Function not in module?!");
245 assert(CMF->getFunctionType() == Funcs[i]->getFunctionType() && "wrong ty");
246 assert(CMF->getName() == Funcs[i]->getName() && "wrong name");
247 Functions.insert(CMF);
250 outs() << "Checking for crash with only these functions: ";
251 PrintFunctionList(Funcs);
253 if (!ReplaceFuncsWithNull) {
254 // Loop over and delete any functions which we aren't supposed to be playing
256 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
257 if (!I->isDeclaration() && !Functions.count(I))
258 DeleteFunctionBody(I);
260 std::vector<GlobalValue*> ToRemove;
261 // First, remove aliases to functions we're about to purge.
262 for (GlobalAlias &Alias : M->aliases()) {
263 Constant *Root = Alias.getAliasee()->stripPointerCasts();
264 Function *F = dyn_cast<Function>(Root);
266 if (Functions.count(F))
267 // We're keeping this function.
269 } else if (Root->isNullValue()) {
270 // This referenced a globalalias that we've already replaced,
271 // so we still need to replace this alias.
273 // Not a function, therefore not something we mess with.
277 PointerType *Ty = cast<PointerType>(Alias.getType());
278 Constant *Replacement = ConstantPointerNull::get(Ty);
279 Alias.replaceAllUsesWith(Replacement);
280 ToRemove.push_back(&Alias);
283 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) {
284 if (!I->isDeclaration() && !Functions.count(I)) {
285 PointerType *Ty = cast<PointerType>(I->getType());
286 Constant *Replacement = ConstantPointerNull::get(Ty);
287 I->replaceAllUsesWith(Replacement);
288 ToRemove.push_back(I);
292 for (auto *F : ToRemove) {
293 F->eraseFromParent();
296 // Finally, remove any null members from any global intrinsic.
297 RemoveFunctionReferences(M, "llvm.used");
298 RemoveFunctionReferences(M, "llvm.compiler.used");
300 // Try running the hacked up program...
302 BD.setNewProgram(M); // It crashed, keep the trimmed version...
304 // Make sure to use function pointers that point into the now-current
306 Funcs.assign(Functions.begin(), Functions.end());
315 /// ReduceCrashingBlocks reducer - This works by setting the terminators of
316 /// all terminators except the specified basic blocks to a 'ret' instruction,
317 /// then running the simplify-cfg pass. This has the effect of chopping up
318 /// the CFG really fast which can reduce large functions quickly.
320 class ReduceCrashingBlocks : public ListReducer<const BasicBlock*> {
322 bool (*TestFn)(const BugDriver &, Module *);
324 ReduceCrashingBlocks(BugDriver &bd,
325 bool (*testFn)(const BugDriver &, Module *))
326 : BD(bd), TestFn(testFn) {}
328 TestResult doTest(std::vector<const BasicBlock*> &Prefix,
329 std::vector<const BasicBlock*> &Kept,
330 std::string &Error) override {
331 if (!Kept.empty() && TestBlocks(Kept))
333 if (!Prefix.empty() && TestBlocks(Prefix))
338 bool TestBlocks(std::vector<const BasicBlock*> &Prefix);
342 bool ReduceCrashingBlocks::TestBlocks(std::vector<const BasicBlock*> &BBs) {
343 // Clone the program to try hacking it apart...
344 ValueToValueMapTy VMap;
345 Module *M = CloneModule(BD.getProgram(), VMap);
347 // Convert list to set for fast lookup...
348 SmallPtrSet<BasicBlock*, 8> Blocks;
349 for (unsigned i = 0, e = BBs.size(); i != e; ++i)
350 Blocks.insert(cast<BasicBlock>(VMap[BBs[i]]));
352 outs() << "Checking for crash with only these blocks:";
353 unsigned NumPrint = Blocks.size();
354 if (NumPrint > 10) NumPrint = 10;
355 for (unsigned i = 0, e = NumPrint; i != e; ++i)
356 outs() << " " << BBs[i]->getName();
357 if (NumPrint < Blocks.size())
358 outs() << "... <" << Blocks.size() << " total>";
361 // Loop over and delete any hack up any blocks that are not listed...
362 for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
363 for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB)
364 if (!Blocks.count(BB) && BB->getTerminator()->getNumSuccessors()) {
365 // Loop over all of the successors of this block, deleting any PHI nodes
366 // that might include it.
367 for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
368 (*SI)->removePredecessor(BB);
370 TerminatorInst *BBTerm = BB->getTerminator();
372 if (!BB->getTerminator()->getType()->isVoidTy())
373 BBTerm->replaceAllUsesWith(Constant::getNullValue(BBTerm->getType()));
375 // Replace the old terminator instruction.
376 BB->getInstList().pop_back();
377 new UnreachableInst(BB->getContext(), BB);
380 // The CFG Simplifier pass may delete one of the basic blocks we are
381 // interested in. If it does we need to take the block out of the list. Make
382 // a "persistent mapping" by turning basic blocks into <function, name> pairs.
383 // This won't work well if blocks are unnamed, but that is just the risk we
385 std::vector<std::pair<std::string, std::string> > BlockInfo;
387 for (BasicBlock *BB : Blocks)
388 BlockInfo.push_back(std::make_pair(BB->getParent()->getName(),
391 // Now run the CFG simplify pass on the function...
392 std::vector<std::string> Passes;
393 Passes.push_back("simplifycfg");
394 Passes.push_back("verify");
395 std::unique_ptr<Module> New = BD.runPassesOn(M, Passes);
398 errs() << "simplifycfg failed!\n";
403 // Try running on the hacked up program...
405 BD.setNewProgram(M); // It crashed, keep the trimmed version...
407 // Make sure to use basic block pointers that point into the now-current
408 // module, and that they don't include any deleted blocks.
410 const ValueSymbolTable &GST = M->getValueSymbolTable();
411 for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
412 Function *F = cast<Function>(GST.lookup(BlockInfo[i].first));
413 ValueSymbolTable &ST = F->getValueSymbolTable();
414 Value* V = ST.lookup(BlockInfo[i].second);
415 if (V && V->getType() == Type::getLabelTy(V->getContext()))
416 BBs.push_back(cast<BasicBlock>(V));
420 delete M; // It didn't crash, try something else.
425 /// ReduceCrashingInstructions reducer - This works by removing the specified
426 /// non-terminator instructions and replacing them with undef.
428 class ReduceCrashingInstructions : public ListReducer<const Instruction*> {
430 bool (*TestFn)(const BugDriver &, Module *);
432 ReduceCrashingInstructions(BugDriver &bd,
433 bool (*testFn)(const BugDriver &, Module *))
434 : BD(bd), TestFn(testFn) {}
436 TestResult doTest(std::vector<const Instruction*> &Prefix,
437 std::vector<const Instruction*> &Kept,
438 std::string &Error) override {
439 if (!Kept.empty() && TestInsts(Kept))
441 if (!Prefix.empty() && TestInsts(Prefix))
446 bool TestInsts(std::vector<const Instruction*> &Prefix);
450 bool ReduceCrashingInstructions::TestInsts(std::vector<const Instruction*>
452 // Clone the program to try hacking it apart...
453 ValueToValueMapTy VMap;
454 Module *M = CloneModule(BD.getProgram(), VMap);
456 // Convert list to set for fast lookup...
457 SmallPtrSet<Instruction*, 64> Instructions;
458 for (unsigned i = 0, e = Insts.size(); i != e; ++i) {
459 assert(!isa<TerminatorInst>(Insts[i]));
460 Instructions.insert(cast<Instruction>(VMap[Insts[i]]));
463 outs() << "Checking for crash with only " << Instructions.size();
464 if (Instructions.size() == 1)
465 outs() << " instruction: ";
467 outs() << " instructions: ";
469 for (Module::iterator MI = M->begin(), ME = M->end(); MI != ME; ++MI)
470 for (Function::iterator FI = MI->begin(), FE = MI->end(); FI != FE; ++FI)
471 for (BasicBlock::iterator I = FI->begin(), E = FI->end(); I != E;) {
472 Instruction *Inst = I++;
473 if (!Instructions.count(Inst) && !isa<TerminatorInst>(Inst) &&
474 !isa<LandingPadInst>(Inst)) {
475 if (!Inst->getType()->isVoidTy())
476 Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
477 Inst->eraseFromParent();
481 // Verify that this is still valid.
482 legacy::PassManager Passes;
483 Passes.add(createVerifierPass());
486 // Try running on the hacked up program...
488 BD.setNewProgram(M); // It crashed, keep the trimmed version...
490 // Make sure to use instruction pointers that point into the now-current
491 // module, and that they don't include any deleted blocks.
493 for (Instruction *Inst : Instructions)
494 Insts.push_back(Inst);
497 delete M; // It didn't crash, try something else.
501 /// DebugACrash - Given a predicate that determines whether a component crashes
502 /// on a program, try to destructively reduce the program while still keeping
503 /// the predicate true.
504 static bool DebugACrash(BugDriver &BD,
505 bool (*TestFn)(const BugDriver &, Module *),
506 std::string &Error) {
507 // See if we can get away with nuking some of the global variable initializers
510 BD.getProgram()->global_begin() != BD.getProgram()->global_end()) {
511 // Now try to reduce the number of global variable initializers in the
512 // module to something small.
513 Module *M = CloneModule(BD.getProgram());
514 bool DeletedInit = false;
516 for (Module::global_iterator I = M->global_begin(), E = M->global_end();
518 if (I->hasInitializer()) {
519 I->setInitializer(nullptr);
520 I->setLinkage(GlobalValue::ExternalLinkage);
525 delete M; // No change made...
527 // See if the program still causes a crash...
528 outs() << "\nChecking to see if we can delete global inits: ";
530 if (TestFn(BD, M)) { // Still crashes?
532 outs() << "\n*** Able to remove all global initializers!\n";
533 } else { // No longer crashes?
534 outs() << " - Removing all global inits hides problem!\n";
537 std::vector<GlobalVariable*> GVs;
539 for (Module::global_iterator I = BD.getProgram()->global_begin(),
540 E = BD.getProgram()->global_end(); I != E; ++I)
541 if (I->hasInitializer())
544 if (GVs.size() > 1 && !BugpointIsInterrupted) {
545 outs() << "\n*** Attempting to reduce the number of global "
546 << "variables in the testcase\n";
548 unsigned OldSize = GVs.size();
549 ReduceCrashingGlobalVariables(BD, TestFn).reduceList(GVs, Error);
553 if (GVs.size() < OldSize)
554 BD.EmitProgressBitcode(BD.getProgram(), "reduced-global-variables");
560 // Now try to reduce the number of functions in the module to something small.
561 std::vector<Function*> Functions;
562 for (Module::iterator I = BD.getProgram()->begin(),
563 E = BD.getProgram()->end(); I != E; ++I)
564 if (!I->isDeclaration())
565 Functions.push_back(I);
567 if (Functions.size() > 1 && !BugpointIsInterrupted) {
568 outs() << "\n*** Attempting to reduce the number of functions "
571 unsigned OldSize = Functions.size();
572 ReduceCrashingFunctions(BD, TestFn).reduceList(Functions, Error);
574 if (Functions.size() < OldSize)
575 BD.EmitProgressBitcode(BD.getProgram(), "reduced-function");
578 // Attempt to delete entire basic blocks at a time to speed up
579 // convergence... this actually works by setting the terminator of the blocks
580 // to a return instruction then running simplifycfg, which can potentially
581 // shrinks the code dramatically quickly
583 if (!DisableSimplifyCFG && !BugpointIsInterrupted) {
584 std::vector<const BasicBlock*> Blocks;
585 for (Module::const_iterator I = BD.getProgram()->begin(),
586 E = BD.getProgram()->end(); I != E; ++I)
587 for (Function::const_iterator FI = I->begin(), E = I->end(); FI !=E; ++FI)
588 Blocks.push_back(FI);
589 unsigned OldSize = Blocks.size();
590 ReduceCrashingBlocks(BD, TestFn).reduceList(Blocks, Error);
591 if (Blocks.size() < OldSize)
592 BD.EmitProgressBitcode(BD.getProgram(), "reduced-blocks");
595 // Attempt to delete instructions using bisection. This should help out nasty
596 // cases with large basic blocks where the problem is at one end.
597 if (!BugpointIsInterrupted) {
598 std::vector<const Instruction*> Insts;
599 for (Module::const_iterator MI = BD.getProgram()->begin(),
600 ME = BD.getProgram()->end(); MI != ME; ++MI)
601 for (Function::const_iterator FI = MI->begin(), FE = MI->end(); FI != FE;
603 for (BasicBlock::const_iterator I = FI->begin(), E = FI->end();
605 if (!isa<TerminatorInst>(I))
608 ReduceCrashingInstructions(BD, TestFn).reduceList(Insts, Error);
611 // FIXME: This should use the list reducer to converge faster by deleting
612 // larger chunks of instructions at a time!
613 unsigned Simplification = 2;
615 if (BugpointIsInterrupted) break;
617 outs() << "\n*** Attempting to reduce testcase by deleting instruc"
618 << "tions: Simplification Level #" << Simplification << '\n';
620 // Now that we have deleted the functions that are unnecessary for the
621 // program, try to remove instructions that are not necessary to cause the
622 // crash. To do this, we loop through all of the instructions in the
623 // remaining functions, deleting them (replacing any values produced with
624 // nulls), and then running ADCE and SimplifyCFG. If the transformed input
625 // still triggers failure, keep deleting until we cannot trigger failure
628 unsigned InstructionsToSkipBeforeDeleting = 0;
631 // Loop over all of the (non-terminator) instructions remaining in the
632 // function, attempting to delete them.
633 unsigned CurInstructionNum = 0;
634 for (Module::const_iterator FI = BD.getProgram()->begin(),
635 E = BD.getProgram()->end(); FI != E; ++FI)
636 if (!FI->isDeclaration())
637 for (Function::const_iterator BI = FI->begin(), E = FI->end(); BI != E;
639 for (BasicBlock::const_iterator I = BI->begin(), E = --BI->end();
640 I != E; ++I, ++CurInstructionNum) {
641 if (InstructionsToSkipBeforeDeleting) {
642 --InstructionsToSkipBeforeDeleting;
644 if (BugpointIsInterrupted) goto ExitLoops;
646 if (isa<LandingPadInst>(I))
649 outs() << "Checking instruction: " << *I;
650 std::unique_ptr<Module> M =
651 BD.deleteInstructionFromProgram(I, Simplification);
653 // Find out if the pass still crashes on this pass...
654 if (TestFn(BD, M.get())) {
655 // Yup, it does, we delete the old module, and continue trying
656 // to reduce the testcase...
657 BD.setNewProgram(M.release());
658 InstructionsToSkipBeforeDeleting = CurInstructionNum;
659 goto TryAgain; // I wish I had a multi-level break here!
664 if (InstructionsToSkipBeforeDeleting) {
665 InstructionsToSkipBeforeDeleting = 0;
669 } while (Simplification);
672 // Try to clean up the testcase by running funcresolve and globaldce...
673 if (!BugpointIsInterrupted) {
674 outs() << "\n*** Attempting to perform final cleanups: ";
675 Module *M = CloneModule(BD.getProgram());
676 M = BD.performFinalCleanups(M, true).release();
678 // Find out if the pass still crashes on the cleaned up program...
680 BD.setNewProgram(M); // Yup, it does, keep the reduced version...
686 BD.EmitProgressBitcode(BD.getProgram(), "reduced-simplified");
691 static bool TestForOptimizerCrash(const BugDriver &BD, Module *M) {
692 return BD.runPasses(M);
695 /// debugOptimizerCrash - This method is called when some pass crashes on input.
696 /// It attempts to prune down the testcase to something reasonable, and figure
697 /// out exactly which pass is crashing.
699 bool BugDriver::debugOptimizerCrash(const std::string &ID) {
700 outs() << "\n*** Debugging optimizer crash!\n";
703 // Reduce the list of passes which causes the optimizer to crash...
704 if (!BugpointIsInterrupted && !DontReducePassList)
705 ReducePassList(*this).reduceList(PassesToRun, Error);
706 assert(Error.empty());
708 outs() << "\n*** Found crashing pass"
709 << (PassesToRun.size() == 1 ? ": " : "es: ")
710 << getPassesString(PassesToRun) << '\n';
712 EmitProgressBitcode(Program, ID);
714 bool Success = DebugACrash(*this, TestForOptimizerCrash, Error);
715 assert(Error.empty());
719 static bool TestForCodeGenCrash(const BugDriver &BD, Module *M) {
721 BD.compileProgram(M, &Error);
722 if (!Error.empty()) {
723 errs() << "<crash>\n";
724 return true; // Tool is still crashing.
730 /// debugCodeGeneratorCrash - This method is called when the code generator
731 /// crashes on an input. It attempts to reduce the input as much as possible
732 /// while still causing the code generator to crash.
733 bool BugDriver::debugCodeGeneratorCrash(std::string &Error) {
734 errs() << "*** Debugging code generator crash!\n";
736 return DebugACrash(*this, TestForCodeGenCrash, Error);