1 //=== WebAssemblyLowerEmscriptenEHSjLj.cpp - Lower exceptions for Emscripten =//
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 //===----------------------------------------------------------------------===//
11 /// \brief This file lowers exception-related instructions and setjmp/longjmp
12 /// function calls in order to use Emscripten's JavaScript try and catch
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
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.
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
51 /// In detail, this pass does following things:
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
66 /// * Exception handling
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
75 /// function setThrew(threw, value) {
76 /// if (__THREW__ == 0) {
77 /// __THREW__ = threw;
78 /// __threwValue = value;
82 /// function setTempRet0(value) {
83 /// __tempRet0 = value;
87 /// invoke @func(arg1, arg2) to label %invoke.cont unwind label %lpad
90 /// call @__invoke_SIG(func, arg1, arg2)
91 /// %__THREW__.val = __THREW__;
93 /// if (%__THREW__.val == 1)
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) {
107 /// Module["dynCall_vi"](index,a1); // This calls original callee
109 /// if (typeof e !== 'number' && e !== 'longjmp') throw e;
110 /// asm["setThrew"](1, 0); // setThrew is called here
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.
117 /// %val = landingpad catch c1 catch c2 catch c3 ...
120 /// %fmc = call @__cxa_find_matching_catch_N(c1, c2, c3, ...)
121 /// %val = {%fmc, __tempRet0}
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
130 /// call @__resumeException(%a)
131 /// where __resumeException() is a function in JS glue code.
134 /// call @llvm.eh.typeid.for(type) (intrinsic)
136 /// call @llvm_eh_typeid_for(type)
137 /// llvm_eh_typeid_for function will be generated in JS glue code.
139 /// * Setjmp / Longjmp handling
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
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.
164 /// longjmp(buf, value)
166 /// emscripten_longjmp_jmpbuf(buf, value)
167 /// emscripten_longjmp_jmpbuf will be lowered to emscripten_longjmp later.
169 /// 10) Lower every call that might longjmp into
171 /// call @__invoke_SIG(func, arg1, arg2)
172 /// %__THREW__.val = __THREW__;
174 /// if (%__THREW__.val != 0 & __threwValue != 0) {
175 /// %label = testSetjmp(mem[%__THREW__.val], setjmpTable,
176 /// setjmpTableSize);
178 /// emscripten_longjmp(%__THREW__.val, __threwValue);
179 /// __tempRet0 = __threwValue;
183 /// longjmp_result = __tempRet0;
185 /// label 1: goto post-setjmp BB 1
186 /// label 2: goto post-setjmp BB 2
188 /// default: goto splitted next BB
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.
206 ///===----------------------------------------------------------------------===//
208 #include "WebAssembly.h"
209 #include "llvm/IR/CallSite.h"
210 #include "llvm/IR/Dominators.h"
211 #include "llvm/IR/IRBuilder.h"
212 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
213 #include "llvm/Transforms/Utils/SSAUpdater.h"
215 using namespace llvm;
217 #define DEBUG_TYPE "wasm-lower-em-ehsjlj"
219 static cl::list<std::string>
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)"),
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;
242 bool EnableEH; // Enable exception handling
243 bool EnableSjLj; // Enable setjmp/longjmp handling
245 GlobalVariable *ThrewGV;
246 GlobalVariable *ThrewValueGV;
247 GlobalVariable *TempRet0GV;
250 Function *EmLongjmpF;
251 Function *EmLongjmpJmpbufF;
252 Function *SaveSetjmpF;
253 Function *TestSetjmpF;
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;
263 StringRef getPassName() const override {
264 return "WebAssembly Lower Emscripten Exceptions";
267 bool runEHOnFunction(Function &F);
268 bool runSjLjOnFunction(Function &F);
269 Function *getFindMatchingCatch(Module &M, unsigned NumClauses);
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);
277 bool areAllExceptionsAllowed() const { return EHWhitelistSet.empty(); }
278 bool canLongjmp(Module &M, const Value *Callee) const;
280 void createSetThrewFunction(Module &M);
281 void createSetTempRet0Function(Module &M);
283 void rebuildSSA(Function &F);
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());
295 bool runOnModule(Module &M) override;
297 void getAnalysisUsage(AnalysisUsage &AU) const override {
298 AU.addRequired<DominatorTreeWrapperPass>();
301 } // End anonymous namespace
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_";
321 char WebAssemblyLowerEmscriptenEHSjLj::ID = 0;
322 INITIALIZE_PASS(WebAssemblyLowerEmscriptenEHSjLj, DEBUG_TYPE,
323 "WebAssembly Lower Emscripten Exceptions / Setjmp / Longjmp",
326 ModulePass *llvm::createWebAssemblyLowerEmscriptenEHSjLj(bool EnableEH,
328 return new WebAssemblyLowerEmscriptenEHSjLj(EnableEH, EnableSjLj);
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())
336 StringRef Name = F->getName();
337 // leave setjmp and longjmp (mostly) alone, we process them properly later
338 if (Name == "setjmp" || Name == "longjmp")
340 return !F->doesNotThrow();
342 // not a function, so an indirect call - can throw, we can't tell
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))
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
362 static std::string getSignature(FunctionType *FTy) {
364 raw_string_ostream OS(Sig);
365 OS << *FTy->getReturnType();
366 for (Type *ParamTy : FTy->params())
367 OS << "_" << *ParamTy;
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(), ',', '.');
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
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);
392 Function::Create(FTy, GlobalValue::ExternalLinkage,
393 FindMatchingCatchPrefix + Twine(NumClauses + 2), &M);
394 FindMatchingCatches[NumClauses] = F;
398 // Generate invoke wrapper seqence with preamble and 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();
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(AttributeList::FunctionIndex, Attribute::NoReturn);
419 IRB.SetInsertPoint(CI);
423 IRB.CreateStore(IRB.getInt32(0), ThrewGV);
425 // Invoke function wrapper in JavaScript
426 SmallVector<Value *, 16> Args;
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());
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> ArgAttributes;
439 const AttributeList &InvokeAL = CI->getAttributes();
441 // No attributes for the callee pointer.
442 ArgAttributes.push_back(AttributeSet());
443 // Copy the argument attributes from the original
444 for (unsigned i = 0, e = CI->getNumArgOperands(); i < e; ++i)
445 ArgAttributes.push_back(InvokeAL.getParamAttributes(i));
447 // Reconstruct the AttributesList based on the vector we constructed.
448 AttributeList NewCallAL =
449 AttributeList::get(C, InvokeAL.getFnAttributes(),
450 InvokeAL.getRetAttributes(), ArgAttributes);
451 NewCall->setAttributes(NewCallAL);
453 CI->replaceAllUsesWith(NewCall);
456 // %__THREW__.val = __THREW__; __THREW__ = 0;
457 Value *Threw = IRB.CreateLoad(ThrewGV, ThrewGV->getName() + ".val");
458 IRB.CreateStore(IRB.getInt32(0), ThrewGV);
462 // Get matching invoke wrapper based on callee signature
463 template <typename CallOrInvoke>
464 Function *WebAssemblyLowerEmscriptenEHSjLj::getInvokeWrapper(CallOrInvoke *CI) {
465 Module *M = CI->getModule();
466 SmallVector<Type *, 16> ArgTys;
467 Value *Callee = CI->getCalledValue();
468 FunctionType *CalleeFTy;
469 if (auto *F = dyn_cast<Function>(Callee))
470 CalleeFTy = F->getFunctionType();
472 auto *CalleeTy = cast<PointerType>(Callee->getType())->getElementType();
473 CalleeFTy = dyn_cast<FunctionType>(CalleeTy);
476 std::string Sig = getSignature(CalleeFTy);
477 if (InvokeWrappers.find(Sig) != InvokeWrappers.end())
478 return InvokeWrappers[Sig];
480 // Put the pointer to the callee as first argument
481 ArgTys.push_back(PointerType::getUnqual(CalleeFTy));
482 // Add argument types
483 ArgTys.append(CalleeFTy->param_begin(), CalleeFTy->param_end());
485 FunctionType *FTy = FunctionType::get(CalleeFTy->getReturnType(), ArgTys,
486 CalleeFTy->isVarArg());
487 Function *F = Function::Create(FTy, GlobalValue::ExternalLinkage,
488 InvokePrefix + Sig, M);
489 InvokeWrappers[Sig] = F;
493 bool WebAssemblyLowerEmscriptenEHSjLj::canLongjmp(Module &M,
494 const Value *Callee) const {
495 if (auto *CalleeF = dyn_cast<Function>(Callee))
496 if (CalleeF->isIntrinsic())
499 // The reason we include malloc/free here is to exclude the malloc/free
500 // calls generated in setjmp prep / cleanup routines.
501 Function *SetjmpF = M.getFunction("setjmp");
502 Function *MallocF = M.getFunction("malloc");
503 Function *FreeF = M.getFunction("free");
504 if (Callee == SetjmpF || Callee == MallocF || Callee == FreeF)
507 // There are functions in JS glue code
508 if (Callee == ResumeF || Callee == EHTypeIDF || Callee == SaveSetjmpF ||
509 Callee == TestSetjmpF)
512 // __cxa_find_matching_catch_N functions cannot longjmp
513 if (Callee->getName().startswith(FindMatchingCatchPrefix))
516 // Exception-catching related functions
517 Function *BeginCatchF = M.getFunction("__cxa_begin_catch");
518 Function *EndCatchF = M.getFunction("__cxa_end_catch");
519 Function *AllocExceptionF = M.getFunction("__cxa_allocate_exception");
520 Function *ThrowF = M.getFunction("__cxa_throw");
521 Function *TerminateF = M.getFunction("__clang_call_terminate");
522 if (Callee == BeginCatchF || Callee == EndCatchF ||
523 Callee == AllocExceptionF || Callee == ThrowF || Callee == TerminateF)
526 // Otherwise we don't know
530 // Generate testSetjmp function call seqence with preamble and postamble.
531 // The code this generates is equivalent to the following JavaScript code:
532 // if (%__THREW__.val != 0 & threwValue != 0) {
533 // %label = _testSetjmp(mem[%__THREW__.val], setjmpTable, setjmpTableSize);
535 // emscripten_longjmp(%__THREW__.val, threwValue);
536 // __tempRet0 = threwValue;
540 // %longjmp_result = __tempRet0;
542 // As output parameters. returns %label, %longjmp_result, and the BB the last
543 // instruction (%longjmp_result = ...) is in.
544 void WebAssemblyLowerEmscriptenEHSjLj::wrapTestSetjmp(
545 BasicBlock *BB, Instruction *InsertPt, Value *Threw, Value *SetjmpTable,
546 Value *SetjmpTableSize, Value *&Label, Value *&LongjmpResult,
547 BasicBlock *&EndBB) {
548 Function *F = BB->getParent();
549 LLVMContext &C = BB->getModule()->getContext();
551 IRB.SetInsertPoint(InsertPt);
553 // if (%__THREW__.val != 0 & threwValue != 0)
554 IRB.SetInsertPoint(BB);
555 BasicBlock *ThenBB1 = BasicBlock::Create(C, "if.then1", F);
556 BasicBlock *ElseBB1 = BasicBlock::Create(C, "if.else1", F);
557 BasicBlock *EndBB1 = BasicBlock::Create(C, "if.end", F);
558 Value *ThrewCmp = IRB.CreateICmpNE(Threw, IRB.getInt32(0));
560 IRB.CreateLoad(ThrewValueGV, ThrewValueGV->getName() + ".val");
561 Value *ThrewValueCmp = IRB.CreateICmpNE(ThrewValue, IRB.getInt32(0));
562 Value *Cmp1 = IRB.CreateAnd(ThrewCmp, ThrewValueCmp, "cmp1");
563 IRB.CreateCondBr(Cmp1, ThenBB1, ElseBB1);
565 // %label = _testSetjmp(mem[%__THREW__.val], _setjmpTable, _setjmpTableSize);
567 IRB.SetInsertPoint(ThenBB1);
568 BasicBlock *ThenBB2 = BasicBlock::Create(C, "if.then2", F);
569 BasicBlock *EndBB2 = BasicBlock::Create(C, "if.end2", F);
570 Value *ThrewInt = IRB.CreateIntToPtr(Threw, Type::getInt32PtrTy(C),
571 Threw->getName() + ".i32p");
573 IRB.CreateLoad(ThrewInt, ThrewInt->getName() + ".loaded");
574 Value *ThenLabel = IRB.CreateCall(
575 TestSetjmpF, {LoadedThrew, SetjmpTable, SetjmpTableSize}, "label");
576 Value *Cmp2 = IRB.CreateICmpEQ(ThenLabel, IRB.getInt32(0));
577 IRB.CreateCondBr(Cmp2, ThenBB2, EndBB2);
579 // emscripten_longjmp(%__THREW__.val, threwValue);
580 IRB.SetInsertPoint(ThenBB2);
581 IRB.CreateCall(EmLongjmpF, {Threw, ThrewValue});
582 IRB.CreateUnreachable();
584 // __tempRet0 = threwValue;
585 IRB.SetInsertPoint(EndBB2);
586 IRB.CreateStore(ThrewValue, TempRet0GV);
587 IRB.CreateBr(EndBB1);
589 IRB.SetInsertPoint(ElseBB1);
590 IRB.CreateBr(EndBB1);
592 // longjmp_result = __tempRet0;
593 IRB.SetInsertPoint(EndBB1);
594 PHINode *LabelPHI = IRB.CreatePHI(IRB.getInt32Ty(), 2, "label");
595 LabelPHI->addIncoming(ThenLabel, EndBB2);
597 LabelPHI->addIncoming(IRB.getInt32(-1), ElseBB1);
599 // Output parameter assignment
602 LongjmpResult = IRB.CreateLoad(TempRet0GV, "longjmp_result");
605 // Create setThrew function
606 // function setThrew(threw, value) {
607 // if (__THREW__ == 0) {
608 // __THREW__ = threw;
609 // __threwValue = value;
612 void WebAssemblyLowerEmscriptenEHSjLj::createSetThrewFunction(Module &M) {
613 LLVMContext &C = M.getContext();
616 assert(!M.getNamedGlobal(SetThrewFName) && "setThrew already exists");
617 Type *Params[] = {IRB.getInt32Ty(), IRB.getInt32Ty()};
618 FunctionType *FTy = FunctionType::get(IRB.getVoidTy(), Params, false);
620 Function::Create(FTy, GlobalValue::ExternalLinkage, SetThrewFName, &M);
621 Argument *Arg1 = &*(F->arg_begin());
622 Argument *Arg2 = &*std::next(F->arg_begin());
623 Arg1->setName("threw");
624 Arg2->setName("value");
625 BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
626 BasicBlock *ThenBB = BasicBlock::Create(C, "if.then", F);
627 BasicBlock *EndBB = BasicBlock::Create(C, "if.end", F);
629 IRB.SetInsertPoint(EntryBB);
630 Value *Threw = IRB.CreateLoad(ThrewGV, ThrewGV->getName() + ".val");
631 Value *Cmp = IRB.CreateICmpEQ(Threw, IRB.getInt32(0), "cmp");
632 IRB.CreateCondBr(Cmp, ThenBB, EndBB);
634 IRB.SetInsertPoint(ThenBB);
635 IRB.CreateStore(Arg1, ThrewGV);
636 IRB.CreateStore(Arg2, ThrewValueGV);
639 IRB.SetInsertPoint(EndBB);
643 // Create setTempRet0 function
644 // function setTempRet0(value) {
645 // __tempRet0 = value;
647 void WebAssemblyLowerEmscriptenEHSjLj::createSetTempRet0Function(Module &M) {
648 LLVMContext &C = M.getContext();
651 assert(!M.getNamedGlobal(SetTempRet0FName) && "setTempRet0 already exists");
652 Type *Params[] = {IRB.getInt32Ty()};
653 FunctionType *FTy = FunctionType::get(IRB.getVoidTy(), Params, false);
655 Function::Create(FTy, GlobalValue::ExternalLinkage, SetTempRet0FName, &M);
656 F->arg_begin()->setName("value");
657 BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
658 IRB.SetInsertPoint(EntryBB);
659 IRB.CreateStore(&*F->arg_begin(), TempRet0GV);
663 void WebAssemblyLowerEmscriptenEHSjLj::rebuildSSA(Function &F) {
664 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
665 DT.recalculate(F); // CFG has been changed
667 for (BasicBlock &BB : F) {
668 for (Instruction &I : BB) {
669 for (auto UI = I.use_begin(), UE = I.use_end(); UI != UE;) {
672 SSA.Initialize(I.getType(), I.getName());
673 SSA.AddAvailableValue(&BB, &I);
674 Instruction *User = cast<Instruction>(U.getUser());
675 if (User->getParent() == &BB)
678 if (PHINode *UserPN = dyn_cast<PHINode>(User))
679 if (UserPN->getIncomingBlock(U) == &BB)
682 if (DT.dominates(&I, User))
684 SSA.RewriteUseAfterInsertions(U);
690 bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
691 LLVMContext &C = M.getContext();
694 Function *SetjmpF = M.getFunction("setjmp");
695 Function *LongjmpF = M.getFunction("longjmp");
696 bool SetjmpUsed = SetjmpF && !SetjmpF->use_empty();
697 bool LongjmpUsed = LongjmpF && !LongjmpF->use_empty();
698 bool DoSjLj = EnableSjLj && (SetjmpUsed || LongjmpUsed);
700 // Create global variables __THREW__, threwValue, and __tempRet0, which are
701 // used in common for both exception handling and setjmp/longjmp handling
702 ThrewGV = new GlobalVariable(M, IRB.getInt32Ty(), false,
703 GlobalValue::ExternalLinkage, IRB.getInt32(0),
704 createGlobalValueName(M, ThrewGVName));
705 ThrewValueGV = new GlobalVariable(
706 M, IRB.getInt32Ty(), false, GlobalValue::ExternalLinkage, IRB.getInt32(0),
707 createGlobalValueName(M, ThrewValueGVName));
708 TempRet0GV = new GlobalVariable(M, IRB.getInt32Ty(), false,
709 GlobalValue::ExternalLinkage, IRB.getInt32(0),
710 createGlobalValueName(M, TempRet0GVName));
712 bool Changed = false;
714 // Exception handling
716 // Register __resumeException function
717 FunctionType *ResumeFTy =
718 FunctionType::get(IRB.getVoidTy(), IRB.getInt8PtrTy(), false);
719 ResumeF = Function::Create(ResumeFTy, GlobalValue::ExternalLinkage,
722 // Register llvm_eh_typeid_for function
723 FunctionType *EHTypeIDTy =
724 FunctionType::get(IRB.getInt32Ty(), IRB.getInt8PtrTy(), false);
725 EHTypeIDF = Function::Create(EHTypeIDTy, GlobalValue::ExternalLinkage,
728 for (Function &F : M) {
729 if (F.isDeclaration())
731 Changed |= runEHOnFunction(F);
735 // Setjmp/longjmp handling
737 Changed = true; // We have setjmp or longjmp somewhere
739 Function *MallocF = M.getFunction("malloc");
740 Function *FreeF = M.getFunction("free");
741 if (!MallocF || !FreeF)
743 "malloc and free must be linked into the module if setjmp is used");
745 // Register saveSetjmp function
746 FunctionType *SetjmpFTy = SetjmpF->getFunctionType();
747 SmallVector<Type *, 4> Params = {SetjmpFTy->getParamType(0),
748 IRB.getInt32Ty(), Type::getInt32PtrTy(C),
751 FunctionType::get(Type::getInt32PtrTy(C), Params, false);
752 SaveSetjmpF = Function::Create(FTy, GlobalValue::ExternalLinkage,
753 SaveSetjmpFName, &M);
755 // Register testSetjmp function
756 Params = {IRB.getInt32Ty(), Type::getInt32PtrTy(C), IRB.getInt32Ty()};
757 FTy = FunctionType::get(IRB.getInt32Ty(), Params, false);
758 TestSetjmpF = Function::Create(FTy, GlobalValue::ExternalLinkage,
759 TestSetjmpFName, &M);
762 // Replace all uses of longjmp with emscripten_longjmp_jmpbuf, which is
763 // defined in JS code
764 EmLongjmpJmpbufF = Function::Create(LongjmpF->getFunctionType(),
765 GlobalValue::ExternalLinkage,
766 EmLongjmpJmpbufFName, &M);
768 LongjmpF->replaceAllUsesWith(EmLongjmpJmpbufF);
770 FTy = FunctionType::get(IRB.getVoidTy(),
771 {IRB.getInt32Ty(), IRB.getInt32Ty()}, false);
773 Function::Create(FTy, GlobalValue::ExternalLinkage, EmLongjmpFName, &M);
775 // Only traverse functions that uses setjmp in order not to insert
776 // unnecessary prep / cleanup code in every function
777 SmallPtrSet<Function *, 8> SetjmpUsers;
778 for (User *U : SetjmpF->users()) {
779 auto *UI = cast<Instruction>(U);
780 SetjmpUsers.insert(UI->getFunction());
782 for (Function *F : SetjmpUsers)
783 runSjLjOnFunction(*F);
787 // Delete unused global variables and functions
788 ThrewGV->eraseFromParent();
789 ThrewValueGV->eraseFromParent();
790 TempRet0GV->eraseFromParent();
792 ResumeF->eraseFromParent();
794 EHTypeIDF->eraseFromParent();
796 EmLongjmpF->eraseFromParent();
798 SaveSetjmpF->eraseFromParent();
800 TestSetjmpF->eraseFromParent();
804 // If we have made any changes while doing exception handling or
805 // setjmp/longjmp handling, we have to create these functions for JavaScript
807 createSetThrewFunction(M);
808 createSetTempRet0Function(M);
813 bool WebAssemblyLowerEmscriptenEHSjLj::runEHOnFunction(Function &F) {
814 Module &M = *F.getParent();
815 LLVMContext &C = F.getContext();
817 bool Changed = false;
818 SmallVector<Instruction *, 64> ToErase;
819 SmallPtrSet<LandingPadInst *, 32> LandingPads;
820 bool AllowExceptions =
821 areAllExceptionsAllowed() || EHWhitelistSet.count(F.getName());
823 for (BasicBlock &BB : F) {
824 auto *II = dyn_cast<InvokeInst>(BB.getTerminator());
828 LandingPads.insert(II->getLandingPadInst());
829 IRB.SetInsertPoint(II);
831 bool NeedInvoke = AllowExceptions && canThrow(II->getCalledValue());
833 // Wrap invoke with invoke wrapper and generate preamble/postamble
834 Value *Threw = wrapInvoke(II);
835 ToErase.push_back(II);
837 // Insert a branch based on __THREW__ variable
838 Value *Cmp = IRB.CreateICmpEQ(Threw, IRB.getInt32(1), "cmp");
839 IRB.CreateCondBr(Cmp, II->getUnwindDest(), II->getNormalDest());
842 // This can't throw, and we don't need this invoke, just replace it with a
844 SmallVector<Value *, 16> Args(II->arg_begin(), II->arg_end());
845 CallInst *NewCall = IRB.CreateCall(II->getCalledValue(), Args);
846 NewCall->takeName(II);
847 NewCall->setCallingConv(II->getCallingConv());
848 NewCall->setDebugLoc(II->getDebugLoc());
849 NewCall->setAttributes(II->getAttributes());
850 II->replaceAllUsesWith(NewCall);
851 ToErase.push_back(II);
853 IRB.CreateBr(II->getNormalDest());
855 // Remove any PHI node entries from the exception destination
856 II->getUnwindDest()->removePredecessor(&BB);
860 // Process resume instructions
861 for (BasicBlock &BB : F) {
862 // Scan the body of the basic block for resumes
863 for (Instruction &I : BB) {
864 auto *RI = dyn_cast<ResumeInst>(&I);
868 // Split the input into legal values
869 Value *Input = RI->getValue();
870 IRB.SetInsertPoint(RI);
871 Value *Low = IRB.CreateExtractValue(Input, 0, "low");
872 // Create a call to __resumeException function
873 IRB.CreateCall(ResumeF, {Low});
874 // Add a terminator to the block
875 IRB.CreateUnreachable();
876 ToErase.push_back(RI);
880 // Process llvm.eh.typeid.for intrinsics
881 for (BasicBlock &BB : F) {
882 for (Instruction &I : BB) {
883 auto *CI = dyn_cast<CallInst>(&I);
886 const Function *Callee = CI->getCalledFunction();
889 if (Callee->getIntrinsicID() != Intrinsic::eh_typeid_for)
892 IRB.SetInsertPoint(CI);
894 IRB.CreateCall(EHTypeIDF, CI->getArgOperand(0), "typeid");
895 CI->replaceAllUsesWith(NewCI);
896 ToErase.push_back(CI);
900 // Look for orphan landingpads, can occur in blocks with no predecessors
901 for (BasicBlock &BB : F) {
902 Instruction *I = BB.getFirstNonPHI();
903 if (auto *LPI = dyn_cast<LandingPadInst>(I))
904 LandingPads.insert(LPI);
907 // Handle all the landingpad for this function together, as multiple invokes
908 // may share a single lp
909 for (LandingPadInst *LPI : LandingPads) {
910 IRB.SetInsertPoint(LPI);
911 SmallVector<Value *, 16> FMCArgs;
912 for (unsigned i = 0, e = LPI->getNumClauses(); i < e; ++i) {
913 Constant *Clause = LPI->getClause(i);
914 // As a temporary workaround for the lack of aggregate varargs support
915 // in the interface between JS and wasm, break out filter operands into
916 // their component elements.
917 if (LPI->isFilter(i)) {
918 auto *ATy = cast<ArrayType>(Clause->getType());
919 for (unsigned j = 0, e = ATy->getNumElements(); j < e; ++j) {
920 Value *EV = IRB.CreateExtractValue(Clause, makeArrayRef(j), "filter");
921 FMCArgs.push_back(EV);
924 FMCArgs.push_back(Clause);
927 // Create a call to __cxa_find_matching_catch_N function
928 Function *FMCF = getFindMatchingCatch(M, FMCArgs.size());
929 CallInst *FMCI = IRB.CreateCall(FMCF, FMCArgs, "fmc");
930 Value *Undef = UndefValue::get(LPI->getType());
931 Value *Pair0 = IRB.CreateInsertValue(Undef, FMCI, 0, "pair0");
933 IRB.CreateLoad(TempRet0GV, TempRet0GV->getName() + ".val");
934 Value *Pair1 = IRB.CreateInsertValue(Pair0, TempRet0, 1, "pair1");
936 LPI->replaceAllUsesWith(Pair1);
937 ToErase.push_back(LPI);
940 // Erase everything we no longer need in this function
941 for (Instruction *I : ToErase)
942 I->eraseFromParent();
947 bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
948 Module &M = *F.getParent();
949 LLVMContext &C = F.getContext();
951 SmallVector<Instruction *, 64> ToErase;
952 // Vector of %setjmpTable values
953 std::vector<Instruction *> SetjmpTableInsts;
954 // Vector of %setjmpTableSize values
955 std::vector<Instruction *> SetjmpTableSizeInsts;
957 // Setjmp preparation
959 // This instruction effectively means %setjmpTableSize = 4.
960 // We create this as an instruction intentionally, and we don't want to fold
961 // this instruction to a constant 4, because this value will be used in
962 // SSAUpdater.AddAvailableValue(...) later.
963 BasicBlock &EntryBB = F.getEntryBlock();
964 BinaryOperator *SetjmpTableSize = BinaryOperator::Create(
965 Instruction::Add, IRB.getInt32(4), IRB.getInt32(0), "setjmpTableSize",
966 &*EntryBB.getFirstInsertionPt());
967 // setjmpTable = (int *) malloc(40);
968 Instruction *SetjmpTable = CallInst::CreateMalloc(
969 SetjmpTableSize, IRB.getInt32Ty(), IRB.getInt32Ty(), IRB.getInt32(40),
970 nullptr, nullptr, "setjmpTable");
971 // setjmpTable[0] = 0;
972 IRB.SetInsertPoint(SetjmpTableSize);
973 IRB.CreateStore(IRB.getInt32(0), SetjmpTable);
974 SetjmpTableInsts.push_back(SetjmpTable);
975 SetjmpTableSizeInsts.push_back(SetjmpTableSize);
977 // Setjmp transformation
978 std::vector<PHINode *> SetjmpRetPHIs;
979 Function *SetjmpF = M.getFunction("setjmp");
980 for (User *U : SetjmpF->users()) {
981 auto *CI = dyn_cast<CallInst>(U);
983 report_fatal_error("Does not support indirect calls to setjmp");
985 BasicBlock *BB = CI->getParent();
986 if (BB->getParent() != &F) // in other function
989 // The tail is everything right after the call, and will be reached once
990 // when setjmp is called, and later when longjmp returns to the setjmp
991 BasicBlock *Tail = SplitBlock(BB, CI->getNextNode());
992 // Add a phi to the tail, which will be the output of setjmp, which
993 // indicates if this is the first call or a longjmp back. The phi directly
994 // uses the right value based on where we arrive from
995 IRB.SetInsertPoint(Tail->getFirstNonPHI());
996 PHINode *SetjmpRet = IRB.CreatePHI(IRB.getInt32Ty(), 2, "setjmp.ret");
998 // setjmp initial call returns 0
999 SetjmpRet->addIncoming(IRB.getInt32(0), BB);
1000 // The proper output is now this, not the setjmp call itself
1001 CI->replaceAllUsesWith(SetjmpRet);
1002 // longjmp returns to the setjmp will add themselves to this phi
1003 SetjmpRetPHIs.push_back(SetjmpRet);
1006 // Our index in the function is our place in the array + 1 to avoid index
1007 // 0, because index 0 means the longjmp is not ours to handle.
1008 IRB.SetInsertPoint(CI);
1009 Value *Args[] = {CI->getArgOperand(0), IRB.getInt32(SetjmpRetPHIs.size()),
1010 SetjmpTable, SetjmpTableSize};
1011 Instruction *NewSetjmpTable =
1012 IRB.CreateCall(SaveSetjmpF, Args, "setjmpTable");
1013 Instruction *NewSetjmpTableSize =
1014 IRB.CreateLoad(TempRet0GV, "setjmpTableSize");
1015 SetjmpTableInsts.push_back(NewSetjmpTable);
1016 SetjmpTableSizeInsts.push_back(NewSetjmpTableSize);
1017 ToErase.push_back(CI);
1020 // Update each call that can longjmp so it can return to a setjmp where
1023 // Because we are creating new BBs while processing and don't want to make
1024 // all these newly created BBs candidates again for longjmp processing, we
1025 // first make the vector of candidate BBs.
1026 std::vector<BasicBlock *> BBs;
1027 for (BasicBlock &BB : F)
1030 // BBs.size() will change within the loop, so we query it every time
1031 for (unsigned i = 0; i < BBs.size(); i++) {
1032 BasicBlock *BB = BBs[i];
1033 for (Instruction &I : *BB) {
1034 assert(!isa<InvokeInst>(&I));
1035 auto *CI = dyn_cast<CallInst>(&I);
1039 const Value *Callee = CI->getCalledValue();
1040 if (!canLongjmp(M, Callee))
1043 Value *Threw = nullptr;
1045 if (Callee->getName().startswith(InvokePrefix)) {
1046 // If invoke wrapper has already been generated for this call in
1047 // previous EH phase, search for the load instruction
1048 // %__THREW__.val = __THREW__;
1049 // in postamble after the invoke wrapper call
1050 LoadInst *ThrewLI = nullptr;
1051 StoreInst *ThrewResetSI = nullptr;
1052 for (auto I = std::next(BasicBlock::iterator(CI)), IE = BB->end();
1054 if (auto *LI = dyn_cast<LoadInst>(I))
1055 if (auto *GV = dyn_cast<GlobalVariable>(LI->getPointerOperand()))
1056 if (GV == ThrewGV) {
1057 Threw = ThrewLI = LI;
1061 // Search for the store instruction after the load above
1063 for (auto I = std::next(BasicBlock::iterator(ThrewLI)), IE = BB->end();
1065 if (auto *SI = dyn_cast<StoreInst>(I))
1066 if (auto *GV = dyn_cast<GlobalVariable>(SI->getPointerOperand()))
1067 if (GV == ThrewGV && SI->getValueOperand() == IRB.getInt32(0)) {
1072 assert(Threw && ThrewLI && "Cannot find __THREW__ load after invoke");
1073 assert(ThrewResetSI && "Cannot find __THREW__ store after invoke");
1074 Tail = SplitBlock(BB, ThrewResetSI->getNextNode());
1077 // Wrap call with invoke wrapper and generate preamble/postamble
1078 Threw = wrapInvoke(CI);
1079 ToErase.push_back(CI);
1080 Tail = SplitBlock(BB, CI->getNextNode());
1083 // We need to replace the terminator in Tail - SplitBlock makes BB go
1084 // straight to Tail, we need to check if a longjmp occurred, and go to the
1085 // right setjmp-tail if so
1086 ToErase.push_back(BB->getTerminator());
1088 // Generate a function call to testSetjmp function and preamble/postamble
1089 // code to figure out (1) whether longjmp occurred (2) if longjmp
1090 // occurred, which setjmp it corresponds to
1091 Value *Label = nullptr;
1092 Value *LongjmpResult = nullptr;
1093 BasicBlock *EndBB = nullptr;
1094 wrapTestSetjmp(BB, CI, Threw, SetjmpTable, SetjmpTableSize, Label,
1095 LongjmpResult, EndBB);
1096 assert(Label && LongjmpResult && EndBB);
1098 // Create switch instruction
1099 IRB.SetInsertPoint(EndBB);
1100 SwitchInst *SI = IRB.CreateSwitch(Label, Tail, SetjmpRetPHIs.size());
1101 // -1 means no longjmp happened, continue normally (will hit the default
1102 // switch case). 0 means a longjmp that is not ours to handle, needs a
1103 // rethrow. Otherwise the index is the same as the index in P+1 (to avoid
1105 for (unsigned i = 0; i < SetjmpRetPHIs.size(); i++) {
1106 SI->addCase(IRB.getInt32(i + 1), SetjmpRetPHIs[i]->getParent());
1107 SetjmpRetPHIs[i]->addIncoming(LongjmpResult, EndBB);
1110 // We are splitting the block here, and must continue to find other calls
1111 // in the block - which is now split. so continue to traverse in the Tail
1112 BBs.push_back(Tail);
1116 // Erase everything we no longer need in this function
1117 for (Instruction *I : ToErase)
1118 I->eraseFromParent();
1120 // Free setjmpTable buffer before each return instruction
1121 for (BasicBlock &BB : F) {
1122 TerminatorInst *TI = BB.getTerminator();
1123 if (isa<ReturnInst>(TI))
1124 CallInst::CreateFree(SetjmpTable, TI);
1127 // Every call to saveSetjmp can change setjmpTable and setjmpTableSize
1128 // (when buffer reallocation occurs)
1130 // setjmpTableSize = 4;
1131 // setjmpTable = (int *) malloc(40);
1132 // setjmpTable[0] = 0;
1135 // setjmpTable = saveSetjmp(buf, label, setjmpTable, setjmpTableSize);
1136 // setjmpTableSize = __tempRet0;
1137 // So we need to make sure the SSA for these variables is valid so that every
1138 // saveSetjmp and testSetjmp calls have the correct arguments.
1139 SSAUpdater SetjmpTableSSA;
1140 SSAUpdater SetjmpTableSizeSSA;
1141 SetjmpTableSSA.Initialize(Type::getInt32PtrTy(C), "setjmpTable");
1142 SetjmpTableSizeSSA.Initialize(Type::getInt32Ty(C), "setjmpTableSize");
1143 for (Instruction *I : SetjmpTableInsts)
1144 SetjmpTableSSA.AddAvailableValue(I->getParent(), I);
1145 for (Instruction *I : SetjmpTableSizeInsts)
1146 SetjmpTableSizeSSA.AddAvailableValue(I->getParent(), I);
1148 for (auto UI = SetjmpTable->use_begin(), UE = SetjmpTable->use_end();
1150 // Grab the use before incrementing the iterator.
1152 // Increment the iterator before removing the use from the list.
1154 if (Instruction *I = dyn_cast<Instruction>(U.getUser()))
1155 if (I->getParent() != &EntryBB)
1156 SetjmpTableSSA.RewriteUse(U);
1158 for (auto UI = SetjmpTableSize->use_begin(), UE = SetjmpTableSize->use_end();
1162 if (Instruction *I = dyn_cast<Instruction>(U.getUser()))
1163 if (I->getParent() != &EntryBB)
1164 SetjmpTableSizeSSA.RewriteUse(U);
1167 // Finally, our modifications to the cfg can break dominance of SSA variables.
1168 // For example, in this code,
1169 // if (x()) { .. setjmp() .. }
1170 // if (y()) { .. longjmp() .. }
1171 // We must split the longjmp block, and it can jump into the block splitted
1172 // from setjmp one. But that means that when we split the setjmp block, it's
1173 // first part no longer dominates its second part - there is a theoretically
1174 // possible control flow path where x() is false, then y() is true and we
1175 // reach the second part of the setjmp block, without ever reaching the first
1176 // part. So, we rebuild SSA form here.