LLVM  4.0.0
WebAssemblyLowerEmscriptenEHSjLj.cpp
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1 //=== WebAssemblyLowerEmscriptenEHSjLj.cpp - Lower exceptions for Emscripten =//
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 /// \file
11 /// \brief This file lowers exception-related instructions and setjmp/longjmp
12 /// function calls in order to use Emscripten's JavaScript try and catch
13 /// mechanism.
14 ///
15 /// To handle exceptions and setjmp/longjmps, this scheme relies on JavaScript's
16 /// try and catch syntax and relevant exception-related libraries implemented
17 /// in JavaScript glue code that will be produced by Emscripten. This is similar
18 /// to the current Emscripten asm.js exception handling in fastcomp. For
19 /// fastcomp's EH / SjLj scheme, see these files in fastcomp LLVM branch:
20 /// (Location: https://github.com/kripken/emscripten-fastcomp)
21 /// lib/Target/JSBackend/NaCl/LowerEmExceptionsPass.cpp
22 /// lib/Target/JSBackend/NaCl/LowerEmSetjmp.cpp
23 /// lib/Target/JSBackend/JSBackend.cpp
24 /// lib/Target/JSBackend/CallHandlers.h
25 ///
26 /// * Exception handling
27 /// This pass lowers invokes and landingpads into library functions in JS glue
28 /// code. Invokes are lowered into function wrappers called invoke wrappers that
29 /// exist in JS side, which wraps the original function call with JS try-catch.
30 /// If an exception occurred, cxa_throw() function in JS side sets some
31 /// variables (see below) so we can check whether an exception occurred from
32 /// wasm code and handle it appropriately.
33 ///
34 /// * Setjmp-longjmp handling
35 /// This pass lowers setjmp to a reasonably-performant approach for emscripten.
36 /// The idea is that each block with a setjmp is broken up into two parts: the
37 /// part containing setjmp and the part right after the setjmp. The latter part
38 /// is either reached from the setjmp, or later from a longjmp. To handle the
39 /// longjmp, all calls that might longjmp are also called using invoke wrappers
40 /// and thus JS / try-catch. JS longjmp() function also sets some variables so
41 /// we can check / whether a longjmp occurred from wasm code. Each block with a
42 /// function call that might longjmp is also split up after the longjmp call.
43 /// After the longjmp call, we check whether a longjmp occurred, and if it did,
44 /// which setjmp it corresponds to, and jump to the right post-setjmp block.
45 /// We assume setjmp-longjmp handling always run after EH handling, which means
46 /// we don't expect any exception-related instructions when SjLj runs.
47 /// FIXME Currently this scheme does not support indirect call of setjmp,
48 /// because of the limitation of the scheme itself. fastcomp does not support it
49 /// either.
50 ///
51 /// In detail, this pass does following things:
52 ///
53 /// 1) Create three global variables: __THREW__, __threwValue, and __tempRet0.
54 /// __tempRet0 will be set within __cxa_find_matching_catch() function in
55 /// JS library, and __THREW__ and __threwValue will be set in invoke wrappers
56 /// in JS glue code. For what invoke wrappers are, refer to 3). These
57 /// variables are used for both exceptions and setjmp/longjmps.
58 /// __THREW__ indicates whether an exception or a longjmp occurred or not. 0
59 /// means nothing occurred, 1 means an exception occurred, and other numbers
60 /// mean a longjmp occurred. In the case of longjmp, __threwValue variable
61 /// indicates the corresponding setjmp buffer the longjmp corresponds to.
62 /// In exception handling, __tempRet0 indicates the type of an exception
63 /// caught, and in setjmp/longjmp, it means the second argument to longjmp
64 /// function.
65 ///
66 /// * Exception handling
67 ///
68 /// 2) Create setThrew and setTempRet0 functions.
69 /// The global variables created in 1) will exist in wasm address space,
70 /// but their values should be set in JS code, so we provide these functions
71 /// as interfaces to JS glue code. These functions are equivalent to the
72 /// following JS functions, which actually exist in asm.js version of JS
73 /// library.
74 ///
75 /// function setThrew(threw, value) {
76 /// if (__THREW__ == 0) {
77 /// __THREW__ = threw;
78 /// __threwValue = value;
79 /// }
80 /// }
81 ///
82 /// function setTempRet0(value) {
83 /// __tempRet0 = value;
84 /// }
85 ///
86 /// 3) Lower
87 /// invoke @func(arg1, arg2) to label %invoke.cont unwind label %lpad
88 /// into
89 /// __THREW__ = 0;
90 /// call @__invoke_SIG(func, arg1, arg2)
91 /// %__THREW__.val = __THREW__;
92 /// __THREW__ = 0;
93 /// if (%__THREW__.val == 1)
94 /// goto %lpad
95 /// else
96 /// goto %invoke.cont
97 /// SIG is a mangled string generated based on the LLVM IR-level function
98 /// signature. After LLVM IR types are lowered to the target wasm types,
99 /// the names for these wrappers will change based on wasm types as well,
100 /// as in invoke_vi (function takes an int and returns void). The bodies of
101 /// these wrappers will be generated in JS glue code, and inside those
102 /// wrappers we use JS try-catch to generate actual exception effects. It
103 /// also calls the original callee function. An example wrapper in JS code
104 /// would look like this:
105 /// function invoke_vi(index,a1) {
106 /// try {
107 /// Module["dynCall_vi"](index,a1); // This calls original callee
108 /// } catch(e) {
109 /// if (typeof e !== 'number' && e !== 'longjmp') throw e;
110 /// asm["setThrew"](1, 0); // setThrew is called here
111 /// }
112 /// }
113 /// If an exception is thrown, __THREW__ will be set to true in a wrapper,
114 /// so we can jump to the right BB based on this value.
115 ///
116 /// 4) Lower
117 /// %val = landingpad catch c1 catch c2 catch c3 ...
118 /// ... use %val ...
119 /// into
120 /// %fmc = call @__cxa_find_matching_catch_N(c1, c2, c3, ...)
121 /// %val = {%fmc, __tempRet0}
122 /// ... use %val ...
123 /// Here N is a number calculated based on the number of clauses.
124 /// Global variable __tempRet0 is set within __cxa_find_matching_catch() in
125 /// JS glue code.
126 ///
127 /// 5) Lower
128 /// resume {%a, %b}
129 /// into
130 /// call @__resumeException(%a)
131 /// where __resumeException() is a function in JS glue code.
132 ///
133 /// 6) Lower
134 /// call @llvm.eh.typeid.for(type) (intrinsic)
135 /// into
136 /// call @llvm_eh_typeid_for(type)
137 /// llvm_eh_typeid_for function will be generated in JS glue code.
138 ///
139 /// * Setjmp / Longjmp handling
140 ///
141 /// 7) In the function entry that calls setjmp, initialize setjmpTable and
142 /// sejmpTableSize as follows:
143 /// setjmpTableSize = 4;
144 /// setjmpTable = (int *) malloc(40);
145 /// setjmpTable[0] = 0;
146 /// setjmpTable and setjmpTableSize are used in saveSetjmp() function in JS
147 /// code.
148 ///
149 /// 8) Lower
150 /// setjmp(buf)
151 /// into
152 /// setjmpTable = saveSetjmp(buf, label, setjmpTable, setjmpTableSize);
153 /// setjmpTableSize = __tempRet0;
154 /// For each dynamic setjmp call, setjmpTable stores its ID (a number which
155 /// is incrementally assigned from 0) and its label (a unique number that
156 /// represents each callsite of setjmp). When we need more entries in
157 /// setjmpTable, it is reallocated in saveSetjmp() in JS code and it will
158 /// return the new table address, and assign the new table size in
159 /// __tempRet0. saveSetjmp also stores the setjmp's ID into the buffer buf.
160 /// A BB with setjmp is split into two after setjmp call in order to make the
161 /// post-setjmp BB the possible destination of longjmp BB.
162 ///
163 /// 9) Lower
164 /// longjmp(buf, value)
165 /// into
166 /// emscripten_longjmp_jmpbuf(buf, value)
167 /// emscripten_longjmp_jmpbuf will be lowered to emscripten_longjmp later.
168 ///
169 /// 10) Lower every call that might longjmp into
170 /// __THREW__ = 0;
171 /// call @__invoke_SIG(func, arg1, arg2)
172 /// %__THREW__.val = __THREW__;
173 /// __THREW__ = 0;
174 /// if (%__THREW__.val != 0 & __threwValue != 0) {
175 /// %label = testSetjmp(mem[%__THREW__.val], setjmpTable,
176 /// setjmpTableSize);
177 /// if (%label == 0)
178 /// emscripten_longjmp(%__THREW__.val, __threwValue);
179 /// __tempRet0 = __threwValue;
180 /// } else {
181 /// %label = -1;
182 /// }
183 /// longjmp_result = __tempRet0;
184 /// switch label {
185 /// label 1: goto post-setjmp BB 1
186 /// label 2: goto post-setjmp BB 2
187 /// ...
188 /// default: goto splitted next BB
189 /// }
190 /// testSetjmp examines setjmpTable to see if there is a matching setjmp
191 /// call. After calling an invoke wrapper, if a longjmp occurred, __THREW__
192 /// will be the address of matching jmp_buf buffer and __threwValue be the
193 /// second argument to longjmp. mem[__THREW__.val] is a setjmp ID that is
194 /// stored in saveSetjmp. testSetjmp returns a setjmp label, a unique ID to
195 /// each setjmp callsite. Label 0 means this longjmp buffer does not
196 /// correspond to one of the setjmp callsites in this function, so in this
197 /// case we just chain the longjmp to the caller. (Here we call
198 /// emscripten_longjmp, which is different from emscripten_longjmp_jmpbuf.
199 /// emscripten_longjmp_jmpbuf takes jmp_buf as its first argument, while
200 /// emscripten_longjmp takes an int. Both of them will eventually be lowered
201 /// to emscripten_longjmp in s2wasm, but here we need two signatures - we
202 /// can't translate an int value to a jmp_buf.)
203 /// Label -1 means no longjmp occurred. Otherwise we jump to the right
204 /// post-setjmp BB based on the label.
205 ///
206 ///===----------------------------------------------------------------------===//
207 
208 #include "WebAssembly.h"
209 #include "llvm/IR/CallSite.h"
210 #include "llvm/IR/Dominators.h"
211 #include "llvm/IR/IRBuilder.h"
214 
215 using namespace llvm;
216 
217 #define DEBUG_TYPE "wasm-lower-em-ehsjlj"
218 
220  EHWhitelist("emscripten-cxx-exceptions-whitelist",
221  cl::desc("The list of function names in which Emscripten-style "
222  "exception handling is enabled (see emscripten "
223  "EMSCRIPTEN_CATCHING_WHITELIST options)"),
225 
226 namespace {
227 class WebAssemblyLowerEmscriptenEHSjLj final : public ModulePass {
228  static const char *ThrewGVName;
229  static const char *ThrewValueGVName;
230  static const char *TempRet0GVName;
231  static const char *ResumeFName;
232  static const char *EHTypeIDFName;
233  static const char *SetThrewFName;
234  static const char *SetTempRet0FName;
235  static const char *EmLongjmpFName;
236  static const char *EmLongjmpJmpbufFName;
237  static const char *SaveSetjmpFName;
238  static const char *TestSetjmpFName;
239  static const char *FindMatchingCatchPrefix;
240  static const char *InvokePrefix;
241 
242  bool EnableEH; // Enable exception handling
243  bool EnableSjLj; // Enable setjmp/longjmp handling
244 
245  GlobalVariable *ThrewGV;
246  GlobalVariable *ThrewValueGV;
247  GlobalVariable *TempRet0GV;
248  Function *ResumeF;
249  Function *EHTypeIDF;
250  Function *EmLongjmpF;
251  Function *EmLongjmpJmpbufF;
252  Function *SaveSetjmpF;
253  Function *TestSetjmpF;
254 
255  // __cxa_find_matching_catch_N functions.
256  // Indexed by the number of clauses in an original landingpad instruction.
257  DenseMap<int, Function *> FindMatchingCatches;
258  // Map of <function signature string, invoke_ wrappers>
259  StringMap<Function *> InvokeWrappers;
260  // Set of whitelisted function names for exception handling
261  std::set<std::string> EHWhitelistSet;
262 
263  StringRef getPassName() const override {
264  return "WebAssembly Lower Emscripten Exceptions";
265  }
266 
267  bool runEHOnFunction(Function &F);
268  bool runSjLjOnFunction(Function &F);
269  Function *getFindMatchingCatch(Module &M, unsigned NumClauses);
270 
271  template <typename CallOrInvoke> Value *wrapInvoke(CallOrInvoke *CI);
272  void wrapTestSetjmp(BasicBlock *BB, Instruction *InsertPt, Value *Threw,
273  Value *SetjmpTable, Value *SetjmpTableSize, Value *&Label,
274  Value *&LongjmpResult, BasicBlock *&EndBB);
275  template <typename CallOrInvoke> Function *getInvokeWrapper(CallOrInvoke *CI);
276 
277  bool areAllExceptionsAllowed() const { return EHWhitelistSet.empty(); }
278  bool canLongjmp(Module &M, const Value *Callee) const;
279 
280  void createSetThrewFunction(Module &M);
281  void createSetTempRet0Function(Module &M);
282 
283  void rebuildSSA(Function &F);
284 
285 public:
286  static char ID;
287 
288  WebAssemblyLowerEmscriptenEHSjLj(bool EnableEH = true, bool EnableSjLj = true)
289  : ModulePass(ID), EnableEH(EnableEH), EnableSjLj(EnableSjLj),
290  ThrewGV(nullptr), ThrewValueGV(nullptr), TempRet0GV(nullptr),
291  ResumeF(nullptr), EHTypeIDF(nullptr), EmLongjmpF(nullptr),
292  EmLongjmpJmpbufF(nullptr), SaveSetjmpF(nullptr), TestSetjmpF(nullptr) {
293  EHWhitelistSet.insert(EHWhitelist.begin(), EHWhitelist.end());
294  }
295  bool runOnModule(Module &M) override;
296 
297  void getAnalysisUsage(AnalysisUsage &AU) const override {
299  }
300 };
301 } // End anonymous namespace
302 
303 const char *WebAssemblyLowerEmscriptenEHSjLj::ThrewGVName = "__THREW__";
304 const char *WebAssemblyLowerEmscriptenEHSjLj::ThrewValueGVName = "__threwValue";
305 const char *WebAssemblyLowerEmscriptenEHSjLj::TempRet0GVName = "__tempRet0";
306 const char *WebAssemblyLowerEmscriptenEHSjLj::ResumeFName = "__resumeException";
307 const char *WebAssemblyLowerEmscriptenEHSjLj::EHTypeIDFName =
308  "llvm_eh_typeid_for";
309 const char *WebAssemblyLowerEmscriptenEHSjLj::SetThrewFName = "setThrew";
310 const char *WebAssemblyLowerEmscriptenEHSjLj::SetTempRet0FName = "setTempRet0";
311 const char *WebAssemblyLowerEmscriptenEHSjLj::EmLongjmpFName =
312  "emscripten_longjmp";
313 const char *WebAssemblyLowerEmscriptenEHSjLj::EmLongjmpJmpbufFName =
314  "emscripten_longjmp_jmpbuf";
315 const char *WebAssemblyLowerEmscriptenEHSjLj::SaveSetjmpFName = "saveSetjmp";
316 const char *WebAssemblyLowerEmscriptenEHSjLj::TestSetjmpFName = "testSetjmp";
317 const char *WebAssemblyLowerEmscriptenEHSjLj::FindMatchingCatchPrefix =
318  "__cxa_find_matching_catch_";
319 const char *WebAssemblyLowerEmscriptenEHSjLj::InvokePrefix = "__invoke_";
320 
322 INITIALIZE_PASS(WebAssemblyLowerEmscriptenEHSjLj, DEBUG_TYPE,
323  "WebAssembly Lower Emscripten Exceptions / Setjmp / Longjmp",
324  false, false)
325 
327  bool EnableSjLj) {
328  return new WebAssemblyLowerEmscriptenEHSjLj(EnableEH, EnableSjLj);
329 }
330 
331 static bool canThrow(const Value *V) {
332  if (const auto *F = dyn_cast<const Function>(V)) {
333  // Intrinsics cannot throw
334  if (F->isIntrinsic())
335  return false;
336  StringRef Name = F->getName();
337  // leave setjmp and longjmp (mostly) alone, we process them properly later
338  if (Name == "setjmp" || Name == "longjmp")
339  return false;
340  return !F->doesNotThrow();
341  }
342  // not a function, so an indirect call - can throw, we can't tell
343  return true;
344 }
345 
346 // Returns an available name for a global value.
347 // If the proposed name already exists in the module, adds '_' at the end of
348 // the name until the name is available.
349 static inline std::string createGlobalValueName(const Module &M,
350  const std::string &Propose) {
351  std::string Name = Propose;
352  while (M.getNamedGlobal(Name))
353  Name += "_";
354  return Name;
355 }
356 
357 // Simple function name mangler.
358 // This function simply takes LLVM's string representation of parameter types
359 // and concatenate them with '_'. There are non-alphanumeric characters but llc
360 // is ok with it, and we need to postprocess these names after the lowering
361 // phase anyway.
362 static std::string getSignature(FunctionType *FTy) {
363  std::string Sig;
364  raw_string_ostream OS(Sig);
365  OS << *FTy->getReturnType();
366  for (Type *ParamTy : FTy->params())
367  OS << "_" << *ParamTy;
368  if (FTy->isVarArg())
369  OS << "_...";
370  Sig = OS.str();
371  Sig.erase(remove_if(Sig, isspace), Sig.end());
372  // When s2wasm parses .s file, a comma means the end of an argument. So a
373  // mangled function name can contain any character but a comma.
374  std::replace(Sig.begin(), Sig.end(), ',', '.');
375  return Sig;
376 }
377 
378 // Returns __cxa_find_matching_catch_N function, where N = NumClauses + 2.
379 // This is because a landingpad instruction contains two more arguments, a
380 // personality function and a cleanup bit, and __cxa_find_matching_catch_N
381 // functions are named after the number of arguments in the original landingpad
382 // instruction.
383 Function *
384 WebAssemblyLowerEmscriptenEHSjLj::getFindMatchingCatch(Module &M,
385  unsigned NumClauses) {
386  if (FindMatchingCatches.count(NumClauses))
387  return FindMatchingCatches[NumClauses];
388  PointerType *Int8PtrTy = Type::getInt8PtrTy(M.getContext());
389  SmallVector<Type *, 16> Args(NumClauses, Int8PtrTy);
390  FunctionType *FTy = FunctionType::get(Int8PtrTy, Args, false);
391  Function *F =
393  FindMatchingCatchPrefix + Twine(NumClauses + 2), &M);
394  FindMatchingCatches[NumClauses] = F;
395  return F;
396 }
397 
398 // Generate invoke wrapper seqence with preamble and postamble
399 // Preamble:
400 // __THREW__ = 0;
401 // Postamble:
402 // %__THREW__.val = __THREW__; __THREW__ = 0;
403 // Returns %__THREW__.val, which indicates whether an exception is thrown (or
404 // whether longjmp occurred), for future use.
405 template <typename CallOrInvoke>
406 Value *WebAssemblyLowerEmscriptenEHSjLj::wrapInvoke(CallOrInvoke *CI) {
407  LLVMContext &C = CI->getModule()->getContext();
408 
409  // If we are calling a function that is noreturn, we must remove that
410  // attribute. The code we insert here does expect it to return, after we
411  // catch the exception.
412  if (CI->doesNotReturn()) {
413  if (auto *F = dyn_cast<Function>(CI->getCalledValue()))
414  F->removeFnAttr(Attribute::NoReturn);
415  CI->removeAttribute(AttributeSet::FunctionIndex, Attribute::NoReturn);
416  }
417 
418  IRBuilder<> IRB(C);
419  IRB.SetInsertPoint(CI);
420 
421  // Pre-invoke
422  // __THREW__ = 0;
423  IRB.CreateStore(IRB.getInt32(0), ThrewGV);
424 
425  // Invoke function wrapper in JavaScript
427  // Put the pointer to the callee as first argument, so it can be called
428  // within the invoke wrapper later
429  Args.push_back(CI->getCalledValue());
430  Args.append(CI->arg_begin(), CI->arg_end());
431  CallInst *NewCall = IRB.CreateCall(getInvokeWrapper(CI), Args);
432  NewCall->takeName(CI);
433  NewCall->setCallingConv(CI->getCallingConv());
434  NewCall->setDebugLoc(CI->getDebugLoc());
435 
436  // Because we added the pointer to the callee as first argument, all
437  // argument attribute indices have to be incremented by one.
438  SmallVector<AttributeSet, 8> AttributesVec;
439  const AttributeSet &InvokePAL = CI->getAttributes();
440  CallSite::arg_iterator AI = CI->arg_begin();
441  unsigned i = 1; // Argument attribute index starts from 1
442  for (unsigned e = CI->getNumArgOperands(); i <= e; ++AI, ++i) {
443  if (InvokePAL.hasAttributes(i)) {
444  AttrBuilder B(InvokePAL, i);
445  AttributesVec.push_back(AttributeSet::get(C, i + 1, B));
446  }
447  }
448  // Add any return attributes.
450  AttributesVec.push_back(AttributeSet::get(C, InvokePAL.getRetAttributes()));
451  // Add any function attributes.
453  AttributesVec.push_back(AttributeSet::get(C, InvokePAL.getFnAttributes()));
454  // Reconstruct the AttributesList based on the vector we constructed.
455  AttributeSet NewCallPAL = AttributeSet::get(C, AttributesVec);
456  NewCall->setAttributes(NewCallPAL);
457 
458  CI->replaceAllUsesWith(NewCall);
459 
460  // Post-invoke
461  // %__THREW__.val = __THREW__; __THREW__ = 0;
462  Value *Threw = IRB.CreateLoad(ThrewGV, ThrewGV->getName() + ".val");
463  IRB.CreateStore(IRB.getInt32(0), ThrewGV);
464  return Threw;
465 }
466 
467 // Get matching invoke wrapper based on callee signature
468 template <typename CallOrInvoke>
469 Function *WebAssemblyLowerEmscriptenEHSjLj::getInvokeWrapper(CallOrInvoke *CI) {
470  Module *M = CI->getModule();
472  Value *Callee = CI->getCalledValue();
473  FunctionType *CalleeFTy;
474  if (auto *F = dyn_cast<Function>(Callee))
475  CalleeFTy = F->getFunctionType();
476  else {
477  auto *CalleeTy = cast<PointerType>(Callee->getType())->getElementType();
478  CalleeFTy = dyn_cast<FunctionType>(CalleeTy);
479  }
480 
481  std::string Sig = getSignature(CalleeFTy);
482  if (InvokeWrappers.find(Sig) != InvokeWrappers.end())
483  return InvokeWrappers[Sig];
484 
485  // Put the pointer to the callee as first argument
486  ArgTys.push_back(PointerType::getUnqual(CalleeFTy));
487  // Add argument types
488  ArgTys.append(CalleeFTy->param_begin(), CalleeFTy->param_end());
489 
490  FunctionType *FTy = FunctionType::get(CalleeFTy->getReturnType(), ArgTys,
491  CalleeFTy->isVarArg());
493  InvokePrefix + Sig, M);
494  InvokeWrappers[Sig] = F;
495  return F;
496 }
497 
498 bool WebAssemblyLowerEmscriptenEHSjLj::canLongjmp(Module &M,
499  const Value *Callee) const {
500  if (auto *CalleeF = dyn_cast<Function>(Callee))
501  if (CalleeF->isIntrinsic())
502  return false;
503 
504  // The reason we include malloc/free here is to exclude the malloc/free
505  // calls generated in setjmp prep / cleanup routines.
506  Function *SetjmpF = M.getFunction("setjmp");
507  Function *MallocF = M.getFunction("malloc");
508  Function *FreeF = M.getFunction("free");
509  if (Callee == SetjmpF || Callee == MallocF || Callee == FreeF)
510  return false;
511 
512  // There are functions in JS glue code
513  if (Callee == ResumeF || Callee == EHTypeIDF || Callee == SaveSetjmpF ||
514  Callee == TestSetjmpF)
515  return false;
516 
517  // __cxa_find_matching_catch_N functions cannot longjmp
518  if (Callee->getName().startswith(FindMatchingCatchPrefix))
519  return false;
520 
521  // Exception-catching related functions
522  Function *BeginCatchF = M.getFunction("__cxa_begin_catch");
523  Function *EndCatchF = M.getFunction("__cxa_end_catch");
524  Function *AllocExceptionF = M.getFunction("__cxa_allocate_exception");
525  Function *ThrowF = M.getFunction("__cxa_throw");
526  Function *TerminateF = M.getFunction("__clang_call_terminate");
527  if (Callee == BeginCatchF || Callee == EndCatchF ||
528  Callee == AllocExceptionF || Callee == ThrowF || Callee == TerminateF)
529  return false;
530 
531  // Otherwise we don't know
532  return true;
533 }
534 
535 // Generate testSetjmp function call seqence with preamble and postamble.
536 // The code this generates is equivalent to the following JavaScript code:
537 // if (%__THREW__.val != 0 & threwValue != 0) {
538 // %label = _testSetjmp(mem[%__THREW__.val], setjmpTable, setjmpTableSize);
539 // if (%label == 0)
540 // emscripten_longjmp(%__THREW__.val, threwValue);
541 // __tempRet0 = threwValue;
542 // } else {
543 // %label = -1;
544 // }
545 // %longjmp_result = __tempRet0;
546 //
547 // As output parameters. returns %label, %longjmp_result, and the BB the last
548 // instruction (%longjmp_result = ...) is in.
549 void WebAssemblyLowerEmscriptenEHSjLj::wrapTestSetjmp(
550  BasicBlock *BB, Instruction *InsertPt, Value *Threw, Value *SetjmpTable,
551  Value *SetjmpTableSize, Value *&Label, Value *&LongjmpResult,
552  BasicBlock *&EndBB) {
553  Function *F = BB->getParent();
554  LLVMContext &C = BB->getModule()->getContext();
555  IRBuilder<> IRB(C);
556  IRB.SetInsertPoint(InsertPt);
557 
558  // if (%__THREW__.val != 0 & threwValue != 0)
559  IRB.SetInsertPoint(BB);
560  BasicBlock *ThenBB1 = BasicBlock::Create(C, "if.then1", F);
561  BasicBlock *ElseBB1 = BasicBlock::Create(C, "if.else1", F);
562  BasicBlock *EndBB1 = BasicBlock::Create(C, "if.end", F);
563  Value *ThrewCmp = IRB.CreateICmpNE(Threw, IRB.getInt32(0));
564  Value *ThrewValue =
565  IRB.CreateLoad(ThrewValueGV, ThrewValueGV->getName() + ".val");
566  Value *ThrewValueCmp = IRB.CreateICmpNE(ThrewValue, IRB.getInt32(0));
567  Value *Cmp1 = IRB.CreateAnd(ThrewCmp, ThrewValueCmp, "cmp1");
568  IRB.CreateCondBr(Cmp1, ThenBB1, ElseBB1);
569 
570  // %label = _testSetjmp(mem[%__THREW__.val], _setjmpTable, _setjmpTableSize);
571  // if (%label == 0)
572  IRB.SetInsertPoint(ThenBB1);
573  BasicBlock *ThenBB2 = BasicBlock::Create(C, "if.then2", F);
574  BasicBlock *EndBB2 = BasicBlock::Create(C, "if.end2", F);
575  Value *ThrewInt = IRB.CreateIntToPtr(Threw, Type::getInt32PtrTy(C),
576  Threw->getName() + ".i32p");
577  Value *LoadedThrew =
578  IRB.CreateLoad(ThrewInt, ThrewInt->getName() + ".loaded");
579  Value *ThenLabel = IRB.CreateCall(
580  TestSetjmpF, {LoadedThrew, SetjmpTable, SetjmpTableSize}, "label");
581  Value *Cmp2 = IRB.CreateICmpEQ(ThenLabel, IRB.getInt32(0));
582  IRB.CreateCondBr(Cmp2, ThenBB2, EndBB2);
583 
584  // emscripten_longjmp(%__THREW__.val, threwValue);
585  IRB.SetInsertPoint(ThenBB2);
586  IRB.CreateCall(EmLongjmpF, {Threw, ThrewValue});
587  IRB.CreateUnreachable();
588 
589  // __tempRet0 = threwValue;
590  IRB.SetInsertPoint(EndBB2);
591  IRB.CreateStore(ThrewValue, TempRet0GV);
592  IRB.CreateBr(EndBB1);
593 
594  IRB.SetInsertPoint(ElseBB1);
595  IRB.CreateBr(EndBB1);
596 
597  // longjmp_result = __tempRet0;
598  IRB.SetInsertPoint(EndBB1);
599  PHINode *LabelPHI = IRB.CreatePHI(IRB.getInt32Ty(), 2, "label");
600  LabelPHI->addIncoming(ThenLabel, EndBB2);
601 
602  LabelPHI->addIncoming(IRB.getInt32(-1), ElseBB1);
603 
604  // Output parameter assignment
605  Label = LabelPHI;
606  EndBB = EndBB1;
607  LongjmpResult = IRB.CreateLoad(TempRet0GV, "longjmp_result");
608 }
609 
610 // Create setThrew function
611 // function setThrew(threw, value) {
612 // if (__THREW__ == 0) {
613 // __THREW__ = threw;
614 // __threwValue = value;
615 // }
616 // }
617 void WebAssemblyLowerEmscriptenEHSjLj::createSetThrewFunction(Module &M) {
618  LLVMContext &C = M.getContext();
619  IRBuilder<> IRB(C);
620 
621  assert(!M.getNamedGlobal(SetThrewFName) && "setThrew already exists");
622  Type *Params[] = {IRB.getInt32Ty(), IRB.getInt32Ty()};
623  FunctionType *FTy = FunctionType::get(IRB.getVoidTy(), Params, false);
624  Function *F =
625  Function::Create(FTy, GlobalValue::ExternalLinkage, SetThrewFName, &M);
626  Argument *Arg1 = &*(F->arg_begin());
627  Argument *Arg2 = &*(++F->arg_begin());
628  Arg1->setName("threw");
629  Arg2->setName("value");
630  BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
631  BasicBlock *ThenBB = BasicBlock::Create(C, "if.then", F);
632  BasicBlock *EndBB = BasicBlock::Create(C, "if.end", F);
633 
634  IRB.SetInsertPoint(EntryBB);
635  Value *Threw = IRB.CreateLoad(ThrewGV, ThrewGV->getName() + ".val");
636  Value *Cmp = IRB.CreateICmpEQ(Threw, IRB.getInt32(0), "cmp");
637  IRB.CreateCondBr(Cmp, ThenBB, EndBB);
638 
639  IRB.SetInsertPoint(ThenBB);
640  IRB.CreateStore(Arg1, ThrewGV);
641  IRB.CreateStore(Arg2, ThrewValueGV);
642  IRB.CreateBr(EndBB);
643 
644  IRB.SetInsertPoint(EndBB);
645  IRB.CreateRetVoid();
646 }
647 
648 // Create setTempRet0 function
649 // function setTempRet0(value) {
650 // __tempRet0 = value;
651 // }
652 void WebAssemblyLowerEmscriptenEHSjLj::createSetTempRet0Function(Module &M) {
653  LLVMContext &C = M.getContext();
654  IRBuilder<> IRB(C);
655 
656  assert(!M.getNamedGlobal(SetTempRet0FName) && "setTempRet0 already exists");
657  Type *Params[] = {IRB.getInt32Ty()};
658  FunctionType *FTy = FunctionType::get(IRB.getVoidTy(), Params, false);
659  Function *F =
660  Function::Create(FTy, GlobalValue::ExternalLinkage, SetTempRet0FName, &M);
661  F->arg_begin()->setName("value");
662  BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
663  IRB.SetInsertPoint(EntryBB);
664  IRB.CreateStore(&*F->arg_begin(), TempRet0GV);
665  IRB.CreateRetVoid();
666 }
667 
668 void WebAssemblyLowerEmscriptenEHSjLj::rebuildSSA(Function &F) {
669  DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
670  DT.recalculate(F); // CFG has been changed
671  SSAUpdater SSA;
672  for (BasicBlock &BB : F) {
673  for (Instruction &I : BB) {
674  for (auto UI = I.use_begin(), UE = I.use_end(); UI != UE;) {
675  Use &U = *UI;
676  ++UI;
677  SSA.Initialize(I.getType(), I.getName());
678  SSA.AddAvailableValue(&BB, &I);
679  Instruction *User = cast<Instruction>(U.getUser());
680  if (User->getParent() == &BB)
681  continue;
682 
683  if (PHINode *UserPN = dyn_cast<PHINode>(User))
684  if (UserPN->getIncomingBlock(U) == &BB)
685  continue;
686 
687  if (DT.dominates(&I, User))
688  continue;
690  }
691  }
692  }
693 }
694 
695 bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
696  LLVMContext &C = M.getContext();
697  IRBuilder<> IRB(C);
698 
699  Function *SetjmpF = M.getFunction("setjmp");
700  Function *LongjmpF = M.getFunction("longjmp");
701  bool SetjmpUsed = SetjmpF && !SetjmpF->use_empty();
702  bool LongjmpUsed = LongjmpF && !LongjmpF->use_empty();
703  bool DoSjLj = EnableSjLj && (SetjmpUsed || LongjmpUsed);
704 
705  // Create global variables __THREW__, threwValue, and __tempRet0, which are
706  // used in common for both exception handling and setjmp/longjmp handling
707  ThrewGV = new GlobalVariable(M, IRB.getInt32Ty(), false,
708  GlobalValue::ExternalLinkage, IRB.getInt32(0),
709  createGlobalValueName(M, ThrewGVName));
710  ThrewValueGV = new GlobalVariable(
711  M, IRB.getInt32Ty(), false, GlobalValue::ExternalLinkage, IRB.getInt32(0),
712  createGlobalValueName(M, ThrewValueGVName));
713  TempRet0GV = new GlobalVariable(M, IRB.getInt32Ty(), false,
714  GlobalValue::ExternalLinkage, IRB.getInt32(0),
715  createGlobalValueName(M, TempRet0GVName));
716 
717  bool Changed = false;
718 
719  // Exception handling
720  if (EnableEH) {
721  // Register __resumeException function
722  FunctionType *ResumeFTy =
723  FunctionType::get(IRB.getVoidTy(), IRB.getInt8PtrTy(), false);
724  ResumeF = Function::Create(ResumeFTy, GlobalValue::ExternalLinkage,
725  ResumeFName, &M);
726 
727  // Register llvm_eh_typeid_for function
728  FunctionType *EHTypeIDTy =
729  FunctionType::get(IRB.getInt32Ty(), IRB.getInt8PtrTy(), false);
730  EHTypeIDF = Function::Create(EHTypeIDTy, GlobalValue::ExternalLinkage,
731  EHTypeIDFName, &M);
732 
733  for (Function &F : M) {
734  if (F.isDeclaration())
735  continue;
736  Changed |= runEHOnFunction(F);
737  }
738  }
739 
740  // Setjmp/longjmp handling
741  if (DoSjLj) {
742  Changed = true; // We have setjmp or longjmp somewhere
743 
744  Function *MallocF = M.getFunction("malloc");
745  Function *FreeF = M.getFunction("free");
746  if (!MallocF || !FreeF)
748  "malloc and free must be linked into the module if setjmp is used");
749 
750  // Register saveSetjmp function
751  FunctionType *SetjmpFTy = SetjmpF->getFunctionType();
752  SmallVector<Type *, 4> Params = {SetjmpFTy->getParamType(0),
754  IRB.getInt32Ty()};
755  FunctionType *FTy =
756  FunctionType::get(Type::getInt32PtrTy(C), Params, false);
758  SaveSetjmpFName, &M);
759 
760  // Register testSetjmp function
761  Params = {IRB.getInt32Ty(), Type::getInt32PtrTy(C), IRB.getInt32Ty()};
762  FTy = FunctionType::get(IRB.getInt32Ty(), Params, false);
764  TestSetjmpFName, &M);
765 
766  if (LongjmpF) {
767  // Replace all uses of longjmp with emscripten_longjmp_jmpbuf, which is
768  // defined in JS code
769  EmLongjmpJmpbufF = Function::Create(LongjmpF->getFunctionType(),
771  EmLongjmpJmpbufFName, &M);
772 
773  LongjmpF->replaceAllUsesWith(EmLongjmpJmpbufF);
774  }
775  FTy = FunctionType::get(IRB.getVoidTy(),
776  {IRB.getInt32Ty(), IRB.getInt32Ty()}, false);
777  EmLongjmpF =
778  Function::Create(FTy, GlobalValue::ExternalLinkage, EmLongjmpFName, &M);
779 
780  // Only traverse functions that uses setjmp in order not to insert
781  // unnecessary prep / cleanup code in every function
782  SmallPtrSet<Function *, 8> SetjmpUsers;
783  for (User *U : SetjmpF->users()) {
784  auto *UI = cast<Instruction>(U);
785  SetjmpUsers.insert(UI->getFunction());
786  }
787  for (Function *F : SetjmpUsers)
788  runSjLjOnFunction(*F);
789  }
790 
791  if (!Changed) {
792  // Delete unused global variables and functions
793  ThrewGV->eraseFromParent();
794  ThrewValueGV->eraseFromParent();
795  TempRet0GV->eraseFromParent();
796  if (ResumeF)
797  ResumeF->eraseFromParent();
798  if (EHTypeIDF)
799  EHTypeIDF->eraseFromParent();
800  if (EmLongjmpF)
801  EmLongjmpF->eraseFromParent();
802  if (SaveSetjmpF)
803  SaveSetjmpF->eraseFromParent();
804  if (TestSetjmpF)
805  TestSetjmpF->eraseFromParent();
806  return false;
807  }
808 
809  // If we have made any changes while doing exception handling or
810  // setjmp/longjmp handling, we have to create these functions for JavaScript
811  // to call.
812  createSetThrewFunction(M);
813  createSetTempRet0Function(M);
814 
815  return true;
816 }
817 
818 bool WebAssemblyLowerEmscriptenEHSjLj::runEHOnFunction(Function &F) {
819  Module &M = *F.getParent();
820  LLVMContext &C = F.getContext();
821  IRBuilder<> IRB(C);
822  bool Changed = false;
825  bool AllowExceptions =
826  areAllExceptionsAllowed() || EHWhitelistSet.count(F.getName());
827 
828  for (BasicBlock &BB : F) {
829  auto *II = dyn_cast<InvokeInst>(BB.getTerminator());
830  if (!II)
831  continue;
832  Changed = true;
833  LandingPads.insert(II->getLandingPadInst());
834  IRB.SetInsertPoint(II);
835 
836  bool NeedInvoke = AllowExceptions && canThrow(II->getCalledValue());
837  if (NeedInvoke) {
838  // Wrap invoke with invoke wrapper and generate preamble/postamble
839  Value *Threw = wrapInvoke(II);
840  ToErase.push_back(II);
841 
842  // Insert a branch based on __THREW__ variable
843  Value *Cmp = IRB.CreateICmpEQ(Threw, IRB.getInt32(1), "cmp");
844  IRB.CreateCondBr(Cmp, II->getUnwindDest(), II->getNormalDest());
845 
846  } else {
847  // This can't throw, and we don't need this invoke, just replace it with a
848  // call+branch
849  SmallVector<Value *, 16> Args(II->arg_begin(), II->arg_end());
850  CallInst *NewCall = IRB.CreateCall(II->getCalledValue(), Args);
851  NewCall->takeName(II);
852  NewCall->setCallingConv(II->getCallingConv());
853  NewCall->setDebugLoc(II->getDebugLoc());
854  NewCall->setAttributes(II->getAttributes());
855  II->replaceAllUsesWith(NewCall);
856  ToErase.push_back(II);
857 
858  IRB.CreateBr(II->getNormalDest());
859 
860  // Remove any PHI node entries from the exception destination
861  II->getUnwindDest()->removePredecessor(&BB);
862  }
863  }
864 
865  // Process resume instructions
866  for (BasicBlock &BB : F) {
867  // Scan the body of the basic block for resumes
868  for (Instruction &I : BB) {
869  auto *RI = dyn_cast<ResumeInst>(&I);
870  if (!RI)
871  continue;
872 
873  // Split the input into legal values
874  Value *Input = RI->getValue();
875  IRB.SetInsertPoint(RI);
876  Value *Low = IRB.CreateExtractValue(Input, 0, "low");
877  // Create a call to __resumeException function
878  IRB.CreateCall(ResumeF, {Low});
879  // Add a terminator to the block
880  IRB.CreateUnreachable();
881  ToErase.push_back(RI);
882  }
883  }
884 
885  // Process llvm.eh.typeid.for intrinsics
886  for (BasicBlock &BB : F) {
887  for (Instruction &I : BB) {
888  auto *CI = dyn_cast<CallInst>(&I);
889  if (!CI)
890  continue;
891  const Function *Callee = CI->getCalledFunction();
892  if (!Callee)
893  continue;
894  if (Callee->getIntrinsicID() != Intrinsic::eh_typeid_for)
895  continue;
896 
897  IRB.SetInsertPoint(CI);
898  CallInst *NewCI =
899  IRB.CreateCall(EHTypeIDF, CI->getArgOperand(0), "typeid");
900  CI->replaceAllUsesWith(NewCI);
901  ToErase.push_back(CI);
902  }
903  }
904 
905  // Look for orphan landingpads, can occur in blocks with no predecesors
906  for (BasicBlock &BB : F) {
907  Instruction *I = BB.getFirstNonPHI();
908  if (auto *LPI = dyn_cast<LandingPadInst>(I))
909  LandingPads.insert(LPI);
910  }
911 
912  // Handle all the landingpad for this function together, as multiple invokes
913  // may share a single lp
914  for (LandingPadInst *LPI : LandingPads) {
915  IRB.SetInsertPoint(LPI);
916  SmallVector<Value *, 16> FMCArgs;
917  for (unsigned i = 0, e = LPI->getNumClauses(); i < e; ++i) {
918  Constant *Clause = LPI->getClause(i);
919  // As a temporary workaround for the lack of aggregate varargs support
920  // in the interface between JS and wasm, break out filter operands into
921  // their component elements.
922  if (LPI->isFilter(i)) {
923  auto *ATy = cast<ArrayType>(Clause->getType());
924  for (unsigned j = 0, e = ATy->getNumElements(); j < e; ++j) {
925  Value *EV = IRB.CreateExtractValue(Clause, makeArrayRef(j), "filter");
926  FMCArgs.push_back(EV);
927  }
928  } else
929  FMCArgs.push_back(Clause);
930  }
931 
932  // Create a call to __cxa_find_matching_catch_N function
933  Function *FMCF = getFindMatchingCatch(M, FMCArgs.size());
934  CallInst *FMCI = IRB.CreateCall(FMCF, FMCArgs, "fmc");
935  Value *Undef = UndefValue::get(LPI->getType());
936  Value *Pair0 = IRB.CreateInsertValue(Undef, FMCI, 0, "pair0");
937  Value *TempRet0 =
938  IRB.CreateLoad(TempRet0GV, TempRet0GV->getName() + ".val");
939  Value *Pair1 = IRB.CreateInsertValue(Pair0, TempRet0, 1, "pair1");
940 
941  LPI->replaceAllUsesWith(Pair1);
942  ToErase.push_back(LPI);
943  }
944 
945  // Erase everything we no longer need in this function
946  for (Instruction *I : ToErase)
947  I->eraseFromParent();
948 
949  return Changed;
950 }
951 
952 bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
953  Module &M = *F.getParent();
954  LLVMContext &C = F.getContext();
955  IRBuilder<> IRB(C);
957  // Vector of %setjmpTable values
958  std::vector<Instruction *> SetjmpTableInsts;
959  // Vector of %setjmpTableSize values
960  std::vector<Instruction *> SetjmpTableSizeInsts;
961 
962  // Setjmp preparation
963 
964  // This instruction effectively means %setjmpTableSize = 4.
965  // We create this as an instruction intentionally, and we don't want to fold
966  // this instruction to a constant 4, because this value will be used in
967  // SSAUpdater.AddAvailableValue(...) later.
968  BasicBlock &EntryBB = F.getEntryBlock();
969  BinaryOperator *SetjmpTableSize = BinaryOperator::Create(
970  Instruction::Add, IRB.getInt32(4), IRB.getInt32(0), "setjmpTableSize",
971  &*EntryBB.getFirstInsertionPt());
972  // setjmpTable = (int *) malloc(40);
973  Instruction *SetjmpTable = CallInst::CreateMalloc(
974  SetjmpTableSize, IRB.getInt32Ty(), IRB.getInt32Ty(), IRB.getInt32(40),
975  nullptr, nullptr, "setjmpTable");
976  // setjmpTable[0] = 0;
977  IRB.SetInsertPoint(SetjmpTableSize);
978  IRB.CreateStore(IRB.getInt32(0), SetjmpTable);
979  SetjmpTableInsts.push_back(SetjmpTable);
980  SetjmpTableSizeInsts.push_back(SetjmpTableSize);
981 
982  // Setjmp transformation
983  std::vector<PHINode *> SetjmpRetPHIs;
984  Function *SetjmpF = M.getFunction("setjmp");
985  for (User *U : SetjmpF->users()) {
986  auto *CI = dyn_cast<CallInst>(U);
987  if (!CI)
988  report_fatal_error("Does not support indirect calls to setjmp");
989 
990  BasicBlock *BB = CI->getParent();
991  if (BB->getParent() != &F) // in other function
992  continue;
993 
994  // The tail is everything right after the call, and will be reached once
995  // when setjmp is called, and later when longjmp returns to the setjmp
996  BasicBlock *Tail = SplitBlock(BB, CI->getNextNode());
997  // Add a phi to the tail, which will be the output of setjmp, which
998  // indicates if this is the first call or a longjmp back. The phi directly
999  // uses the right value based on where we arrive from
1000  IRB.SetInsertPoint(Tail->getFirstNonPHI());
1001  PHINode *SetjmpRet = IRB.CreatePHI(IRB.getInt32Ty(), 2, "setjmp.ret");
1002 
1003  // setjmp initial call returns 0
1004  SetjmpRet->addIncoming(IRB.getInt32(0), BB);
1005  // The proper output is now this, not the setjmp call itself
1006  CI->replaceAllUsesWith(SetjmpRet);
1007  // longjmp returns to the setjmp will add themselves to this phi
1008  SetjmpRetPHIs.push_back(SetjmpRet);
1009 
1010  // Fix call target
1011  // Our index in the function is our place in the array + 1 to avoid index
1012  // 0, because index 0 means the longjmp is not ours to handle.
1013  IRB.SetInsertPoint(CI);
1014  Value *Args[] = {CI->getArgOperand(0), IRB.getInt32(SetjmpRetPHIs.size()),
1015  SetjmpTable, SetjmpTableSize};
1016  Instruction *NewSetjmpTable =
1017  IRB.CreateCall(SaveSetjmpF, Args, "setjmpTable");
1018  Instruction *NewSetjmpTableSize =
1019  IRB.CreateLoad(TempRet0GV, "setjmpTableSize");
1020  SetjmpTableInsts.push_back(NewSetjmpTable);
1021  SetjmpTableSizeInsts.push_back(NewSetjmpTableSize);
1022  ToErase.push_back(CI);
1023  }
1024 
1025  // Update each call that can longjmp so it can return to a setjmp where
1026  // relevant.
1027 
1028  // Because we are creating new BBs while processing and don't want to make
1029  // all these newly created BBs candidates again for longjmp processing, we
1030  // first make the vector of candidate BBs.
1031  std::vector<BasicBlock *> BBs;
1032  for (BasicBlock &BB : F)
1033  BBs.push_back(&BB);
1034 
1035  // BBs.size() will change within the loop, so we query it every time
1036  for (unsigned i = 0; i < BBs.size(); i++) {
1037  BasicBlock *BB = BBs[i];
1038  for (Instruction &I : *BB) {
1039  assert(!isa<InvokeInst>(&I));
1040  auto *CI = dyn_cast<CallInst>(&I);
1041  if (!CI)
1042  continue;
1043 
1044  const Value *Callee = CI->getCalledValue();
1045  if (!canLongjmp(M, Callee))
1046  continue;
1047 
1048  Value *Threw = nullptr;
1049  BasicBlock *Tail;
1050  if (Callee->getName().startswith(InvokePrefix)) {
1051  // If invoke wrapper has already been generated for this call in
1052  // previous EH phase, search for the load instruction
1053  // %__THREW__.val = __THREW__;
1054  // in postamble after the invoke wrapper call
1055  LoadInst *ThrewLI = nullptr;
1056  StoreInst *ThrewResetSI = nullptr;
1057  for (auto I = std::next(BasicBlock::iterator(CI)), IE = BB->end();
1058  I != IE; ++I) {
1059  if (auto *LI = dyn_cast<LoadInst>(I))
1060  if (auto *GV = dyn_cast<GlobalVariable>(LI->getPointerOperand()))
1061  if (GV == ThrewGV) {
1062  Threw = ThrewLI = LI;
1063  break;
1064  }
1065  }
1066  // Search for the store instruction after the load above
1067  // __THREW__ = 0;
1068  for (auto I = std::next(BasicBlock::iterator(ThrewLI)), IE = BB->end();
1069  I != IE; ++I) {
1070  if (auto *SI = dyn_cast<StoreInst>(I))
1071  if (auto *GV = dyn_cast<GlobalVariable>(SI->getPointerOperand()))
1072  if (GV == ThrewGV && SI->getValueOperand() == IRB.getInt32(0)) {
1073  ThrewResetSI = SI;
1074  break;
1075  }
1076  }
1077  assert(Threw && ThrewLI && "Cannot find __THREW__ load after invoke");
1078  assert(ThrewResetSI && "Cannot find __THREW__ store after invoke");
1079  Tail = SplitBlock(BB, ThrewResetSI->getNextNode());
1080 
1081  } else {
1082  // Wrap call with invoke wrapper and generate preamble/postamble
1083  Threw = wrapInvoke(CI);
1084  ToErase.push_back(CI);
1085  Tail = SplitBlock(BB, CI->getNextNode());
1086  }
1087 
1088  // We need to replace the terminator in Tail - SplitBlock makes BB go
1089  // straight to Tail, we need to check if a longjmp occurred, and go to the
1090  // right setjmp-tail if so
1091  ToErase.push_back(BB->getTerminator());
1092 
1093  // Generate a function call to testSetjmp function and preamble/postamble
1094  // code to figure out (1) whether longjmp occurred (2) if longjmp
1095  // occurred, which setjmp it corresponds to
1096  Value *Label = nullptr;
1097  Value *LongjmpResult = nullptr;
1098  BasicBlock *EndBB = nullptr;
1099  wrapTestSetjmp(BB, CI, Threw, SetjmpTable, SetjmpTableSize, Label,
1100  LongjmpResult, EndBB);
1101  assert(Label && LongjmpResult && EndBB);
1102 
1103  // Create switch instruction
1104  IRB.SetInsertPoint(EndBB);
1105  SwitchInst *SI = IRB.CreateSwitch(Label, Tail, SetjmpRetPHIs.size());
1106  // -1 means no longjmp happened, continue normally (will hit the default
1107  // switch case). 0 means a longjmp that is not ours to handle, needs a
1108  // rethrow. Otherwise the index is the same as the index in P+1 (to avoid
1109  // 0).
1110  for (unsigned i = 0; i < SetjmpRetPHIs.size(); i++) {
1111  SI->addCase(IRB.getInt32(i + 1), SetjmpRetPHIs[i]->getParent());
1112  SetjmpRetPHIs[i]->addIncoming(LongjmpResult, EndBB);
1113  }
1114 
1115  // We are splitting the block here, and must continue to find other calls
1116  // in the block - which is now split. so continue to traverse in the Tail
1117  BBs.push_back(Tail);
1118  }
1119  }
1120 
1121  // Erase everything we no longer need in this function
1122  for (Instruction *I : ToErase)
1123  I->eraseFromParent();
1124 
1125  // Free setjmpTable buffer before each return instruction
1126  for (BasicBlock &BB : F) {
1127  TerminatorInst *TI = BB.getTerminator();
1128  if (isa<ReturnInst>(TI))
1129  CallInst::CreateFree(SetjmpTable, TI);
1130  }
1131 
1132  // Every call to saveSetjmp can change setjmpTable and setjmpTableSize
1133  // (when buffer reallocation occurs)
1134  // entry:
1135  // setjmpTableSize = 4;
1136  // setjmpTable = (int *) malloc(40);
1137  // setjmpTable[0] = 0;
1138  // ...
1139  // somebb:
1140  // setjmpTable = saveSetjmp(buf, label, setjmpTable, setjmpTableSize);
1141  // setjmpTableSize = __tempRet0;
1142  // So we need to make sure the SSA for these variables is valid so that every
1143  // saveSetjmp and testSetjmp calls have the correct arguments.
1144  SSAUpdater SetjmpTableSSA;
1145  SSAUpdater SetjmpTableSizeSSA;
1146  SetjmpTableSSA.Initialize(Type::getInt32PtrTy(C), "setjmpTable");
1147  SetjmpTableSizeSSA.Initialize(Type::getInt32Ty(C), "setjmpTableSize");
1148  for (Instruction *I : SetjmpTableInsts)
1149  SetjmpTableSSA.AddAvailableValue(I->getParent(), I);
1150  for (Instruction *I : SetjmpTableSizeInsts)
1151  SetjmpTableSizeSSA.AddAvailableValue(I->getParent(), I);
1152 
1153  for (auto UI = SetjmpTable->use_begin(), UE = SetjmpTable->use_end();
1154  UI != UE;) {
1155  // Grab the use before incrementing the iterator.
1156  Use &U = *UI;
1157  // Increment the iterator before removing the use from the list.
1158  ++UI;
1159  if (Instruction *I = dyn_cast<Instruction>(U.getUser()))
1160  if (I->getParent() != &EntryBB)
1161  SetjmpTableSSA.RewriteUse(U);
1162  }
1163  for (auto UI = SetjmpTableSize->use_begin(), UE = SetjmpTableSize->use_end();
1164  UI != UE;) {
1165  Use &U = *UI;
1166  ++UI;
1167  if (Instruction *I = dyn_cast<Instruction>(U.getUser()))
1168  if (I->getParent() != &EntryBB)
1169  SetjmpTableSizeSSA.RewriteUse(U);
1170  }
1171 
1172  // Finally, our modifications to the cfg can break dominance of SSA variables.
1173  // For example, in this code,
1174  // if (x()) { .. setjmp() .. }
1175  // if (y()) { .. longjmp() .. }
1176  // We must split the longjmp block, and it can jump into the block splitted
1177  // from setjmp one. But that means that when we split the setjmp block, it's
1178  // first part no longer dominates its second part - there is a theoretically
1179  // possible control flow path where x() is false, then y() is true and we
1180  // reach the second part of the setjmp block, without ever reaching the first
1181  // part. So, we rebuild SSA form here.
1182  rebuildSSA(F);
1183  return true;
1184 }
SymbolTableList< Instruction >::iterator eraseFromParent()
This method unlinks 'this' from the containing basic block and deletes it.
Definition: Instruction.cpp:76
use_iterator use_end()
Definition: Value.h:318
Helper class for SSA formation on a set of values defined in multiple blocks.
Definition: SSAUpdater.h:38
void addIncoming(Value *V, BasicBlock *BB)
Add an incoming value to the end of the PHI list.
ModulePass * createWebAssemblyLowerEmscriptenEHSjLj(bool DoEH, bool DoSjLj)
LLVMContext & getContext() const
getContext - Return a reference to the LLVMContext associated with this function. ...
Definition: Function.cpp:226
LLVM Argument representation.
Definition: Argument.h:34
NodeTy * getNextNode()
Get the next node, or nullptr for the list tail.
Definition: ilist_node.h:274
LLVM_ATTRIBUTE_NORETURN void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
size_t i
BasicBlock * SplitBlock(BasicBlock *Old, Instruction *SplitPt, DominatorTree *DT=nullptr, LoopInfo *LI=nullptr)
Split the specified block at the specified instruction - everything before SplitPt stays in Old and e...
void Initialize(Type *Ty, StringRef Name)
Reset this object to get ready for a new set of SSA updates with type 'Ty'.
Definition: SSAUpdater.cpp:45
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:52
auto remove_if(R &&Range, UnaryPredicate P) -> decltype(std::begin(Range))
Provide wrappers to std::remove_if which take ranges instead of having to pass begin/end explicitly...
Definition: STLExtras.h:776
void AddAvailableValue(BasicBlock *BB, Value *V)
Indicate that a rewritten value is available in the specified block with the specified value...
Definition: SSAUpdater.cpp:58
void addCase(ConstantInt *OnVal, BasicBlock *Dest)
Add an entry to the switch instruction.
This class represents a function call, abstracting a target machine's calling convention.
ArrayRef< Type * > params() const
Definition: DerivedTypes.h:128
size_type count(PtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:380
static PointerType * getInt32PtrTy(LLVMContext &C, unsigned AS=0)
Definition: Type.cpp:221
Externally visible function.
Definition: GlobalValue.h:49
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:100
An instruction for reading from memory.
Definition: Instructions.h:164
static Instruction * CreateFree(Value *Source, Instruction *InsertBefore)
Generate the IR for a call to the builtin free function.
This file contains the entry points for global functions defined in the LLVM WebAssembly back-end...
static bool canThrow(const Value *V)
AttributeSet getRetAttributes() const
The attributes for the ret value are returned.
Definition: Attributes.cpp:976
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:191
void setCallingConv(CallingConv::ID CC)
AnalysisUsage & addRequired()
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:81
ArrayRef< T > makeArrayRef(const T &OneElt)
Construct an ArrayRef from a single element.
Definition: ArrayRef.h:440
const Module * getModule() const
Return the module owning the function this basic block belongs to, or nullptr it the function does no...
Definition: BasicBlock.cpp:116
A Use represents the edge between a Value definition and its users.
Definition: Use.h:56
param_iterator param_end() const
Definition: DerivedTypes.h:127
Instruction * getFirstNonPHI()
Returns a pointer to the first instruction in this block that is not a PHINode instruction.
Definition: BasicBlock.cpp:180
This provides a uniform API for creating instructions and inserting them into a basic block: either a...
Definition: IRBuilder.h:588
void setName(const Twine &Name)
Change the name of the value.
Definition: Value.cpp:257
void eraseFromParent() override
eraseFromParent - This method unlinks 'this' from the containing module and deletes it...
Definition: Globals.cpp:319
Class to represent function types.
Definition: DerivedTypes.h:102
#define F(x, y, z)
Definition: MD5.cpp:51
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE bool startswith(StringRef Prefix) const
Check if this string starts with the given Prefix.
Definition: StringRef.h:264
Memory SSA
Definition: MemorySSA.cpp:55
static FunctionType * get(Type *Result, ArrayRef< Type * > Params, bool isVarArg)
This static method is the primary way of constructing a FunctionType.
Definition: Type.cpp:291
static GCRegistry::Add< OcamlGC > B("ocaml","ocaml 3.10-compatible GC")
An instruction for storing to memory.
Definition: Instructions.h:300
void replaceAllUsesWith(Value *V)
Change all uses of this to point to a new Value.
Definition: Value.cpp:401
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:263
Concrete subclass of DominatorTreeBase that is used to compute a normal dominator tree...
Definition: Dominators.h:96
Class to represent pointers.
Definition: DerivedTypes.h:443
void setAttributes(AttributeSet Attrs)
Set the parameter attributes for this call.
Function * getFunction(StringRef Name) const
Look up the specified function in the module symbol table.
Definition: Module.cpp:196
Type * getParamType(unsigned i) const
Parameter type accessors.
Definition: DerivedTypes.h:133
The landingpad instruction holds all of the information necessary to generate correct exception handl...
Subclasses of this class are all able to terminate a basic block.
Definition: InstrTypes.h:52
void setDebugLoc(DebugLoc Loc)
Set the debug location information for this instruction.
Definition: Instruction.h:256
LLVM Basic Block Representation.
Definition: BasicBlock.h:51
The instances of the Type class are immutable: once they are created, they are never changed...
Definition: Type.h:45
This is an important class for using LLVM in a threaded context.
Definition: LLVMContext.h:48
void RewriteUseAfterInsertions(Use &U)
Rewrite a use like RewriteUse but handling in-block definitions.
Definition: SSAUpdater.cpp:195
This is an important base class in LLVM.
Definition: Constant.h:42
Resume the propagation of an exception.
param_iterator param_begin() const
Definition: DerivedTypes.h:126
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:368
Represent the analysis usage information of a pass.
User * getUser() const
Returns the User that contains this Use.
Definition: Use.cpp:41
static BasicBlock * Create(LLVMContext &Context, const Twine &Name="", Function *Parent=nullptr, BasicBlock *InsertBefore=nullptr)
Creates a new BasicBlock.
Definition: BasicBlock.h:93
void append(in_iter in_start, in_iter in_end)
Add the specified range to the end of the SmallVector.
Definition: SmallVector.h:392
static UndefValue * get(Type *T)
Static factory methods - Return an 'undef' object of the specified type.
Definition: Constants.cpp:1337
static PointerType * getInt8PtrTy(LLVMContext &C, unsigned AS=0)
Definition: Type.cpp:213
std::string & str()
Flushes the stream contents to the target string and returns the string's reference.
Definition: raw_ostream.h:479
User::op_iterator arg_iterator
arg_iterator - The type of iterator to use when looping over actual arguments at this call site...
Definition: CallSite.h:205
bool dominates(const Instruction *Def, const Use &U) const
Return true if Def dominates a use in User.
Definition: Dominators.cpp:218
Iterator for intrusive lists based on ilist_node.
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:425
static PointerType * getUnqual(Type *ElementType)
This constructs a pointer to an object of the specified type in the generic address space (address sp...
Definition: DerivedTypes.h:458
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:843
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:230
GlobalVariable * getNamedGlobal(StringRef Name)
Return the global variable in the module with the specified name, of arbitrary type.
Definition: Module.h:357
const BasicBlock & getEntryBlock() const
Definition: Function.h:519
Intrinsic::ID getIntrinsicID() const LLVM_READONLY
getIntrinsicID - This method returns the ID number of the specified function, or Intrinsic::not_intri...
Definition: Function.h:146
static GCRegistry::Add< ShadowStackGC > C("shadow-stack","Very portable GC for uncooperative code generators")
StringMap - This is an unconventional map that is specialized for handling keys that are "strings"...
Definition: StringMap.h:223
static BinaryOperator * Create(BinaryOps Op, Value *S1, Value *S2, const Twine &Name=Twine(), Instruction *InsertBefore=nullptr)
Construct a binary instruction, given the opcode and the two operands.
iterator_range< user_iterator > users()
Definition: Value.h:370
INITIALIZE_PASS(WebAssemblyLowerEmscriptenEHSjLj, DEBUG_TYPE,"WebAssembly Lower Emscripten Exceptions / Setjmp / Longjmp", false, false) ModulePass *llvm
static Instruction * CreateMalloc(Instruction *InsertBefore, Type *IntPtrTy, Type *AllocTy, Value *AllocSize, Value *ArraySize=nullptr, Function *MallocF=nullptr, const Twine &Name="")
Generate the IR for a call to malloc:
use_iterator use_begin()
Definition: Value.h:310
static IntegerType * getInt32Ty(LLVMContext &C)
Definition: Type.cpp:169
bool hasAttributes(unsigned Index) const
Return true if attribute exists at the given index.
#define I(x, y, z)
Definition: MD5.cpp:54
LLVM_ATTRIBUTE_ALWAYS_INLINE size_type size() const
Definition: SmallVector.h:135
FunctionType * getFunctionType() const
Returns the FunctionType for me.
Definition: Function.cpp:230
ModulePass class - This class is used to implement unstructured interprocedural optimizations and ana...
Definition: Pass.h:235
uint64_t Arg2
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:287
size_t size() const
Definition: BasicBlock.h:238
void removeFnAttr(Attribute::AttrKind Kind)
Remove function attributes from this function.
Definition: Function.h:197
static std::string createGlobalValueName(const Module &M, const std::string &Propose)
bool isVarArg() const
Definition: DerivedTypes.h:122
Multiway switch.
bool use_empty() const
Definition: Value.h:299
Type * getReturnType() const
Definition: DerivedTypes.h:123
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
A raw_ostream that writes to an std::string.
Definition: raw_ostream.h:463
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:537
LLVM Value Representation.
Definition: Value.h:71
Invoke instruction.
void recalculate(FT &F)
recalculate - compute a dominator tree for the given function
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:47
static Function * Create(FunctionType *Ty, LinkageTypes Linkage, const Twine &N="", Module *M=nullptr)
Definition: Function.h:117
Legacy analysis pass which computes a DominatorTree.
Definition: Dominators.h:217
iterator getFirstInsertionPt()
Returns an iterator to the first instruction in this block that is suitable for inserting a non-PHI i...
Definition: BasicBlock.cpp:209
void RewriteUse(Use &U)
Rewrite a use of the symbolic value.
Definition: SSAUpdater.cpp:178
static std::string getSignature(FunctionType *FTy)
const BasicBlock * getParent() const
Definition: Instruction.h:62
LLVMContext & getContext() const
Get the global data context.
Definition: Module.h:222
static cl::list< std::string > EHWhitelist("emscripten-cxx-exceptions-whitelist", cl::desc("The list of function names in which Emscripten-style ""exception handling is enabled (see emscripten ""EMSCRIPTEN_CATCHING_WHITELIST options)"), cl::CommaSeparated)
AttributeSet getFnAttributes() const
The function attributes are returned.
Definition: Attributes.cpp:985