/Users/buildslave/jenkins/sharedspace/clang-stage2-coverage-R@2/llvm/lib/CodeGen/DwarfEHPrepare.cpp
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1 | | //===- DwarfEHPrepare - Prepare exception handling for code generation ----===// |
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 pass mulches exception handling code into a form adapted to code |
11 | | // generation. Required if using dwarf exception handling. |
12 | | // |
13 | | //===----------------------------------------------------------------------===// |
14 | | |
15 | | #include "llvm/ADT/BitVector.h" |
16 | | #include "llvm/ADT/SmallVector.h" |
17 | | #include "llvm/ADT/Statistic.h" |
18 | | #include "llvm/Analysis/CFG.h" |
19 | | #include "llvm/Analysis/EHPersonalities.h" |
20 | | #include "llvm/Analysis/TargetTransformInfo.h" |
21 | | #include "llvm/CodeGen/RuntimeLibcalls.h" |
22 | | #include "llvm/CodeGen/TargetPassConfig.h" |
23 | | #include "llvm/IR/BasicBlock.h" |
24 | | #include "llvm/IR/Constants.h" |
25 | | #include "llvm/IR/DerivedTypes.h" |
26 | | #include "llvm/IR/Dominators.h" |
27 | | #include "llvm/IR/Function.h" |
28 | | #include "llvm/IR/Instructions.h" |
29 | | #include "llvm/IR/Module.h" |
30 | | #include "llvm/IR/Type.h" |
31 | | #include "llvm/Pass.h" |
32 | | #include "llvm/Support/Casting.h" |
33 | | #include "llvm/Target/TargetLowering.h" |
34 | | #include "llvm/Target/TargetMachine.h" |
35 | | #include "llvm/Target/TargetSubtargetInfo.h" |
36 | | #include "llvm/Transforms/Utils/Local.h" |
37 | | #include <cstddef> |
38 | | |
39 | | using namespace llvm; |
40 | | |
41 | | #define DEBUG_TYPE "dwarfehprepare" |
42 | | |
43 | | STATISTIC(NumResumesLowered, "Number of resume calls lowered"); |
44 | | |
45 | | namespace { |
46 | | |
47 | | class DwarfEHPrepare : public FunctionPass { |
48 | | // RewindFunction - _Unwind_Resume or the target equivalent. |
49 | | Constant *RewindFunction = nullptr; |
50 | | |
51 | | DominatorTree *DT = nullptr; |
52 | | const TargetLowering *TLI = nullptr; |
53 | | |
54 | | bool InsertUnwindResumeCalls(Function &Fn); |
55 | | Value *GetExceptionObject(ResumeInst *RI); |
56 | | size_t |
57 | | pruneUnreachableResumes(Function &Fn, |
58 | | SmallVectorImpl<ResumeInst *> &Resumes, |
59 | | SmallVectorImpl<LandingPadInst *> &CleanupLPads); |
60 | | |
61 | | public: |
62 | | static char ID; // Pass identification, replacement for typeid. |
63 | | |
64 | 31.4k | DwarfEHPrepare() : FunctionPass(ID) {} |
65 | | |
66 | | bool runOnFunction(Function &Fn) override; |
67 | | |
68 | 31.3k | bool doFinalization(Module &M) override { |
69 | 31.3k | RewindFunction = nullptr; |
70 | 31.3k | return false; |
71 | 31.3k | } |
72 | | |
73 | | void getAnalysisUsage(AnalysisUsage &AU) const override; |
74 | | |
75 | 17 | StringRef getPassName() const override { |
76 | 17 | return "Exception handling preparation"; |
77 | 17 | } |
78 | | }; |
79 | | |
80 | | } // end anonymous namespace |
81 | | |
82 | | char DwarfEHPrepare::ID = 0; |
83 | | |
84 | 42.0k | INITIALIZE_PASS_BEGIN42.0k (DwarfEHPrepare, DEBUG_TYPE,
|
85 | 42.0k | "Prepare DWARF exceptions", false, false) |
86 | 42.0k | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) |
87 | 42.0k | INITIALIZE_PASS_DEPENDENCY(TargetPassConfig) |
88 | 42.0k | INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) |
89 | 42.0k | INITIALIZE_PASS_END(DwarfEHPrepare, DEBUG_TYPE, |
90 | | "Prepare DWARF exceptions", false, false) |
91 | | |
92 | 31.4k | FunctionPass *llvm::createDwarfEHPass() { return new DwarfEHPrepare(); } |
93 | | |
94 | 31.4k | void DwarfEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const { |
95 | 31.4k | AU.addRequired<TargetPassConfig>(); |
96 | 31.4k | AU.addRequired<TargetTransformInfoWrapperPass>(); |
97 | 31.4k | AU.addRequired<DominatorTreeWrapperPass>(); |
98 | 31.4k | } |
99 | | |
100 | | /// GetExceptionObject - Return the exception object from the value passed into |
101 | | /// the 'resume' instruction (typically an aggregate). Clean up any dead |
102 | | /// instructions, including the 'resume' instruction. |
103 | 2.90k | Value *DwarfEHPrepare::GetExceptionObject(ResumeInst *RI) { |
104 | 2.90k | Value *V = RI->getOperand(0); |
105 | 2.90k | Value *ExnObj = nullptr; |
106 | 2.90k | InsertValueInst *SelIVI = dyn_cast<InsertValueInst>(V); |
107 | 2.90k | LoadInst *SelLoad = nullptr; |
108 | 2.90k | InsertValueInst *ExcIVI = nullptr; |
109 | 2.90k | bool EraseIVIs = false; |
110 | 2.90k | |
111 | 2.90k | if (SelIVI2.90k ) { |
112 | 818 | if (SelIVI->getNumIndices() == 1 && 818 *SelIVI->idx_begin() == 1818 ) { |
113 | 818 | ExcIVI = dyn_cast<InsertValueInst>(SelIVI->getOperand(0)); |
114 | 818 | if (ExcIVI && 818 isa<UndefValue>(ExcIVI->getOperand(0))818 && |
115 | 818 | ExcIVI->getNumIndices() == 1818 && *ExcIVI->idx_begin() == 0818 ) { |
116 | 818 | ExnObj = ExcIVI->getOperand(1); |
117 | 818 | SelLoad = dyn_cast<LoadInst>(SelIVI->getOperand(1)); |
118 | 818 | EraseIVIs = true; |
119 | 818 | } |
120 | 818 | } |
121 | 818 | } |
122 | 2.90k | |
123 | 2.90k | if (!ExnObj) |
124 | 2.09k | ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI); |
125 | 2.90k | |
126 | 2.90k | RI->eraseFromParent(); |
127 | 2.90k | |
128 | 2.90k | if (EraseIVIs2.90k ) { |
129 | 818 | if (SelIVI->use_empty()) |
130 | 818 | SelIVI->eraseFromParent(); |
131 | 818 | if (ExcIVI->use_empty()) |
132 | 818 | ExcIVI->eraseFromParent(); |
133 | 818 | if (SelLoad && 818 SelLoad->use_empty()21 ) |
134 | 21 | SelLoad->eraseFromParent(); |
135 | 818 | } |
136 | 2.90k | |
137 | 2.90k | return ExnObj; |
138 | 2.90k | } |
139 | | |
140 | | /// Replace resumes that are not reachable from a cleanup landing pad with |
141 | | /// unreachable and then simplify those blocks. |
142 | | size_t DwarfEHPrepare::pruneUnreachableResumes( |
143 | | Function &Fn, SmallVectorImpl<ResumeInst *> &Resumes, |
144 | 2.72k | SmallVectorImpl<LandingPadInst *> &CleanupLPads) { |
145 | 2.72k | BitVector ResumeReachable(Resumes.size()); |
146 | 2.72k | size_t ResumeIndex = 0; |
147 | 2.93k | for (auto *RI : Resumes) { |
148 | 4.20k | for (auto *LP : CleanupLPads) { |
149 | 4.20k | if (isPotentiallyReachable(LP, RI, DT)4.20k ) { |
150 | 2.90k | ResumeReachable.set(ResumeIndex); |
151 | 2.90k | break; |
152 | 2.90k | } |
153 | 2.93k | } |
154 | 2.93k | ++ResumeIndex; |
155 | 2.93k | } |
156 | 2.72k | |
157 | 2.72k | // If everything is reachable, there is no change. |
158 | 2.72k | if (ResumeReachable.all()) |
159 | 2.69k | return Resumes.size(); |
160 | 30 | |
161 | 30 | const TargetTransformInfo &TTI = |
162 | 30 | getAnalysis<TargetTransformInfoWrapperPass>().getTTI(Fn); |
163 | 30 | LLVMContext &Ctx = Fn.getContext(); |
164 | 30 | |
165 | 30 | // Otherwise, insert unreachable instructions and call simplifycfg. |
166 | 30 | size_t ResumesLeft = 0; |
167 | 60 | for (size_t I = 0, E = Resumes.size(); I < E60 ; ++I30 ) { |
168 | 30 | ResumeInst *RI = Resumes[I]; |
169 | 30 | if (ResumeReachable[I]30 ) { |
170 | 0 | Resumes[ResumesLeft++] = RI; |
171 | 30 | } else { |
172 | 30 | BasicBlock *BB = RI->getParent(); |
173 | 30 | new UnreachableInst(Ctx, RI); |
174 | 30 | RI->eraseFromParent(); |
175 | 30 | SimplifyCFG(BB, TTI); |
176 | 30 | } |
177 | 30 | } |
178 | 2.72k | Resumes.resize(ResumesLeft); |
179 | 2.72k | return ResumesLeft; |
180 | 2.72k | } |
181 | | |
182 | | /// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present |
183 | | /// into calls to the appropriate _Unwind_Resume function. |
184 | 576k | bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) { |
185 | 576k | SmallVector<ResumeInst*, 16> Resumes; |
186 | 576k | SmallVector<LandingPadInst*, 16> CleanupLPads; |
187 | 3.70M | for (BasicBlock &BB : Fn) { |
188 | 3.70M | if (auto *RI = dyn_cast<ResumeInst>(BB.getTerminator())) |
189 | 2.93k | Resumes.push_back(RI); |
190 | 3.70M | if (auto *LP = BB.getLandingPadInst()) |
191 | 13.5k | if (13.5k LP->isCleanup()13.5k ) |
192 | 8.65k | CleanupLPads.push_back(LP); |
193 | 3.70M | } |
194 | 576k | |
195 | 576k | if (Resumes.empty()) |
196 | 574k | return false; |
197 | 2.72k | |
198 | 2.72k | // Check the personality, don't do anything if it's funclet-based. |
199 | 2.72k | EHPersonality Pers = classifyEHPersonality(Fn.getPersonalityFn()); |
200 | 2.72k | if (isFuncletEHPersonality(Pers)) |
201 | 0 | return false; |
202 | 2.72k | |
203 | 2.72k | LLVMContext &Ctx = Fn.getContext(); |
204 | 2.72k | |
205 | 2.72k | size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads); |
206 | 2.72k | if (ResumesLeft == 0) |
207 | 30 | return true; // We pruned them all. |
208 | 2.69k | |
209 | 2.69k | // Find the rewind function if we didn't already. |
210 | 2.69k | if (2.69k !RewindFunction2.69k ) { |
211 | 416 | FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), |
212 | 416 | Type::getInt8PtrTy(Ctx), false); |
213 | 416 | const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); |
214 | 416 | RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy); |
215 | 416 | } |
216 | 2.69k | |
217 | 2.69k | // Create the basic block where the _Unwind_Resume call will live. |
218 | 2.69k | if (ResumesLeft == 12.69k ) { |
219 | 2.52k | // Instead of creating a new BB and PHI node, just append the call to |
220 | 2.52k | // _Unwind_Resume to the end of the single resume block. |
221 | 2.52k | ResumeInst *RI = Resumes.front(); |
222 | 2.52k | BasicBlock *UnwindBB = RI->getParent(); |
223 | 2.52k | Value *ExnObj = GetExceptionObject(RI); |
224 | 2.52k | |
225 | 2.52k | // Call the _Unwind_Resume function. |
226 | 2.52k | CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB); |
227 | 2.52k | CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); |
228 | 2.52k | |
229 | 2.52k | // We never expect _Unwind_Resume to return. |
230 | 2.52k | new UnreachableInst(Ctx, UnwindBB); |
231 | 2.52k | return true; |
232 | 2.52k | } |
233 | 173 | |
234 | 173 | BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn); |
235 | 173 | PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesLeft, |
236 | 173 | "exn.obj", UnwindBB); |
237 | 173 | |
238 | 173 | // Extract the exception object from the ResumeInst and add it to the PHI node |
239 | 173 | // that feeds the _Unwind_Resume call. |
240 | 383 | for (ResumeInst *RI : Resumes) { |
241 | 383 | BasicBlock *Parent = RI->getParent(); |
242 | 383 | BranchInst::Create(UnwindBB, Parent); |
243 | 383 | |
244 | 383 | Value *ExnObj = GetExceptionObject(RI); |
245 | 383 | PN->addIncoming(ExnObj, Parent); |
246 | 383 | |
247 | 383 | ++NumResumesLowered; |
248 | 383 | } |
249 | 576k | |
250 | 576k | // Call the function. |
251 | 576k | CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB); |
252 | 576k | CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); |
253 | 576k | |
254 | 576k | // We never expect _Unwind_Resume to return. |
255 | 576k | new UnreachableInst(Ctx, UnwindBB); |
256 | 576k | return true; |
257 | 576k | } |
258 | | |
259 | 576k | bool DwarfEHPrepare::runOnFunction(Function &Fn) { |
260 | 576k | const TargetMachine &TM = |
261 | 576k | getAnalysis<TargetPassConfig>().getTM<TargetMachine>(); |
262 | 576k | DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); |
263 | 576k | TLI = TM.getSubtargetImpl(Fn)->getTargetLowering(); |
264 | 576k | bool Changed = InsertUnwindResumeCalls(Fn); |
265 | 576k | DT = nullptr; |
266 | 576k | TLI = nullptr; |
267 | 576k | return Changed; |
268 | 576k | } |