Bug Summary

File:llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
Warning:line 334, column 10
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name WebAssemblyLowerEmscriptenEHSjLj.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mthread-model posix -mframe-pointer=none -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-10/lib/clang/10.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/build-llvm/lib/Target/WebAssembly -I /build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/llvm/lib/Target/WebAssembly -I /build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/build-llvm/include -I /build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-10/lib/clang/10.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/build-llvm/lib/Target/WebAssembly -fdebug-prefix-map=/build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc=. -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2020-01-07-154523-9282-1 -x c++ /build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp
1//=== WebAssemblyLowerEmscriptenEHSjLj.cpp - Lower exceptions for Emscripten =//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8///
9/// \file
10/// This file lowers exception-related instructions and setjmp/longjmp
11/// function calls in order to use Emscripten's JavaScript try and catch
12/// mechanism.
13///
14/// To handle exceptions and setjmp/longjmps, this scheme relies on JavaScript's
15/// try and catch syntax and relevant exception-related libraries implemented
16/// in JavaScript glue code that will be produced by Emscripten. This is similar
17/// to the current Emscripten asm.js exception handling in fastcomp. For
18/// fastcomp's EH / SjLj scheme, see these files in fastcomp LLVM branch:
19/// (Location: https://github.com/kripken/emscripten-fastcomp)
20/// lib/Target/JSBackend/NaCl/LowerEmExceptionsPass.cpp
21/// lib/Target/JSBackend/NaCl/LowerEmSetjmp.cpp
22/// lib/Target/JSBackend/JSBackend.cpp
23/// lib/Target/JSBackend/CallHandlers.h
24///
25/// * Exception handling
26/// This pass lowers invokes and landingpads into library functions in JS glue
27/// code. Invokes are lowered into function wrappers called invoke wrappers that
28/// exist in JS side, which wraps the original function call with JS try-catch.
29/// If an exception occurred, cxa_throw() function in JS side sets some
30/// variables (see below) so we can check whether an exception occurred from
31/// wasm code and handle it appropriately.
32///
33/// * Setjmp-longjmp handling
34/// This pass lowers setjmp to a reasonably-performant approach for emscripten.
35/// The idea is that each block with a setjmp is broken up into two parts: the
36/// part containing setjmp and the part right after the setjmp. The latter part
37/// is either reached from the setjmp, or later from a longjmp. To handle the
38/// longjmp, all calls that might longjmp are also called using invoke wrappers
39/// and thus JS / try-catch. JS longjmp() function also sets some variables so
40/// we can check / whether a longjmp occurred from wasm code. Each block with a
41/// function call that might longjmp is also split up after the longjmp call.
42/// After the longjmp call, we check whether a longjmp occurred, and if it did,
43/// which setjmp it corresponds to, and jump to the right post-setjmp block.
44/// We assume setjmp-longjmp handling always run after EH handling, which means
45/// we don't expect any exception-related instructions when SjLj runs.
46/// FIXME Currently this scheme does not support indirect call of setjmp,
47/// because of the limitation of the scheme itself. fastcomp does not support it
48/// either.
49///
50/// In detail, this pass does following things:
51///
52/// 1) Assumes the existence of global variables: __THREW__, __threwValue
53/// __THREW__ and __threwValue will be set in invoke wrappers
54/// in JS glue code. For what invoke wrappers are, refer to 3). These
55/// variables are used for both exceptions and setjmp/longjmps.
56/// __THREW__ indicates whether an exception or a longjmp occurred or not. 0
57/// means nothing occurred, 1 means an exception occurred, and other numbers
58/// mean a longjmp occurred. In the case of longjmp, __threwValue variable
59/// indicates the corresponding setjmp buffer the longjmp corresponds to.
60///
61/// * Exception handling
62///
63/// 2) We assume the existence of setThrew and setTempRet0/getTempRet0 functions
64/// at link time.
65/// The global variables in 1) will exist in wasm address space,
66/// but their values should be set in JS code, so these functions
67/// as interfaces to JS glue code. These functions are equivalent to the
68/// following JS functions, which actually exist in asm.js version of JS
69/// library.
70///
71/// function setThrew(threw, value) {
72/// if (__THREW__ == 0) {
73/// __THREW__ = threw;
74/// __threwValue = value;
75/// }
76/// }
77//
78/// setTempRet0 is called from __cxa_find_matching_catch() in JS glue code.
79///
80/// In exception handling, getTempRet0 indicates the type of an exception
81/// caught, and in setjmp/longjmp, it means the second argument to longjmp
82/// function.
83///
84/// 3) Lower
85/// invoke @func(arg1, arg2) to label %invoke.cont unwind label %lpad
86/// into
87/// __THREW__ = 0;
88/// call @__invoke_SIG(func, arg1, arg2)
89/// %__THREW__.val = __THREW__;
90/// __THREW__ = 0;
91/// if (%__THREW__.val == 1)
92/// goto %lpad
93/// else
94/// goto %invoke.cont
95/// SIG is a mangled string generated based on the LLVM IR-level function
96/// signature. After LLVM IR types are lowered to the target wasm types,
97/// the names for these wrappers will change based on wasm types as well,
98/// as in invoke_vi (function takes an int and returns void). The bodies of
99/// these wrappers will be generated in JS glue code, and inside those
100/// wrappers we use JS try-catch to generate actual exception effects. It
101/// also calls the original callee function. An example wrapper in JS code
102/// would look like this:
103/// function invoke_vi(index,a1) {
104/// try {
105/// Module["dynCall_vi"](index,a1); // This calls original callee
106/// } catch(e) {
107/// if (typeof e !== 'number' && e !== 'longjmp') throw e;
108/// asm["setThrew"](1, 0); // setThrew is called here
109/// }
110/// }
111/// If an exception is thrown, __THREW__ will be set to true in a wrapper,
112/// so we can jump to the right BB based on this value.
113///
114/// 4) Lower
115/// %val = landingpad catch c1 catch c2 catch c3 ...
116/// ... use %val ...
117/// into
118/// %fmc = call @__cxa_find_matching_catch_N(c1, c2, c3, ...)
119/// %val = {%fmc, getTempRet0()}
120/// ... use %val ...
121/// Here N is a number calculated based on the number of clauses.
122/// setTempRet0 is called from __cxa_find_matching_catch() in JS glue code.
123///
124/// 5) Lower
125/// resume {%a, %b}
126/// into
127/// call @__resumeException(%a)
128/// where __resumeException() is a function in JS glue code.
129///
130/// 6) Lower
131/// call @llvm.eh.typeid.for(type) (intrinsic)
132/// into
133/// call @llvm_eh_typeid_for(type)
134/// llvm_eh_typeid_for function will be generated in JS glue code.
135///
136/// * Setjmp / Longjmp handling
137///
138/// In case calls to longjmp() exists
139///
140/// 1) Lower
141/// longjmp(buf, value)
142/// into
143/// emscripten_longjmp_jmpbuf(buf, value)
144/// emscripten_longjmp_jmpbuf will be lowered to emscripten_longjmp later.
145///
146/// In case calls to setjmp() exists
147///
148/// 2) In the function entry that calls setjmp, initialize setjmpTable and
149/// sejmpTableSize as follows:
150/// setjmpTableSize = 4;
151/// setjmpTable = (int *) malloc(40);
152/// setjmpTable[0] = 0;
153/// setjmpTable and setjmpTableSize are used in saveSetjmp() function in JS
154/// code.
155///
156/// 3) Lower
157/// setjmp(buf)
158/// into
159/// setjmpTable = saveSetjmp(buf, label, setjmpTable, setjmpTableSize);
160/// setjmpTableSize = getTempRet0();
161/// For each dynamic setjmp call, setjmpTable stores its ID (a number which
162/// is incrementally assigned from 0) and its label (a unique number that
163/// represents each callsite of setjmp). When we need more entries in
164/// setjmpTable, it is reallocated in saveSetjmp() in JS code and it will
165/// return the new table address, and assign the new table size in
166/// setTempRet0(). saveSetjmp also stores the setjmp's ID into the buffer
167/// buf. A BB with setjmp is split into two after setjmp call in order to
168/// make the post-setjmp BB the possible destination of longjmp BB.
169///
170///
171/// 4) Lower every call that might longjmp into
172/// __THREW__ = 0;
173/// call @__invoke_SIG(func, arg1, arg2)
174/// %__THREW__.val = __THREW__;
175/// __THREW__ = 0;
176/// if (%__THREW__.val != 0 & __threwValue != 0) {
177/// %label = testSetjmp(mem[%__THREW__.val], setjmpTable,
178/// setjmpTableSize);
179/// if (%label == 0)
180/// emscripten_longjmp(%__THREW__.val, __threwValue);
181/// setTempRet0(__threwValue);
182/// } else {
183/// %label = -1;
184/// }
185/// longjmp_result = getTempRet0();
186/// switch label {
187/// label 1: goto post-setjmp BB 1
188/// label 2: goto post-setjmp BB 2
189/// ...
190/// default: goto splitted next BB
191/// }
192/// testSetjmp examines setjmpTable to see if there is a matching setjmp
193/// call. After calling an invoke wrapper, if a longjmp occurred, __THREW__
194/// will be the address of matching jmp_buf buffer and __threwValue be the
195/// second argument to longjmp. mem[__THREW__.val] is a setjmp ID that is
196/// stored in saveSetjmp. testSetjmp returns a setjmp label, a unique ID to
197/// each setjmp callsite. Label 0 means this longjmp buffer does not
198/// correspond to one of the setjmp callsites in this function, so in this
199/// case we just chain the longjmp to the caller. (Here we call
200/// emscripten_longjmp, which is different from emscripten_longjmp_jmpbuf.
201/// emscripten_longjmp_jmpbuf takes jmp_buf as its first argument, while
202/// emscripten_longjmp takes an int. Both of them will eventually be lowered
203/// to emscripten_longjmp in s2wasm, but here we need two signatures - we
204/// can't translate an int value to a jmp_buf.)
205/// Label -1 means no longjmp occurred. Otherwise we jump to the right
206/// post-setjmp BB based on the label.
207///
208///===----------------------------------------------------------------------===//
209
210#include "WebAssembly.h"
211#include "llvm/IR/CallSite.h"
212#include "llvm/IR/Dominators.h"
213#include "llvm/IR/IRBuilder.h"
214#include "llvm/Support/CommandLine.h"
215#include "llvm/Transforms/Utils/BasicBlockUtils.h"
216#include "llvm/Transforms/Utils/SSAUpdater.h"
217
218using namespace llvm;
219
220#define DEBUG_TYPE"wasm-lower-em-ehsjlj" "wasm-lower-em-ehsjlj"
221
222static cl::list<std::string>
223 EHWhitelist("emscripten-cxx-exceptions-whitelist",
224 cl::desc("The list of function names in which Emscripten-style "
225 "exception handling is enabled (see emscripten "
226 "EMSCRIPTEN_CATCHING_WHITELIST options)"),
227 cl::CommaSeparated);
228
229namespace {
230class WebAssemblyLowerEmscriptenEHSjLj final : public ModulePass {
231 bool EnableEH; // Enable exception handling
232 bool EnableSjLj; // Enable setjmp/longjmp handling
233
234 GlobalVariable *ThrewGV = nullptr;
235 GlobalVariable *ThrewValueGV = nullptr;
236 Function *GetTempRet0Func = nullptr;
237 Function *SetTempRet0Func = nullptr;
238 Function *ResumeF = nullptr;
239 Function *EHTypeIDF = nullptr;
240 Function *EmLongjmpF = nullptr;
241 Function *EmLongjmpJmpbufF = nullptr;
242 Function *SaveSetjmpF = nullptr;
243 Function *TestSetjmpF = nullptr;
244
245 // __cxa_find_matching_catch_N functions.
246 // Indexed by the number of clauses in an original landingpad instruction.
247 DenseMap<int, Function *> FindMatchingCatches;
248 // Map of <function signature string, invoke_ wrappers>
249 StringMap<Function *> InvokeWrappers;
250 // Set of whitelisted function names for exception handling
251 std::set<std::string> EHWhitelistSet;
252
253 StringRef getPassName() const override {
254 return "WebAssembly Lower Emscripten Exceptions";
255 }
256
257 bool runEHOnFunction(Function &F);
258 bool runSjLjOnFunction(Function &F);
259 Function *getFindMatchingCatch(Module &M, unsigned NumClauses);
260
261 template <typename CallOrInvoke> Value *wrapInvoke(CallOrInvoke *CI);
262 void wrapTestSetjmp(BasicBlock *BB, Instruction *InsertPt, Value *Threw,
263 Value *SetjmpTable, Value *SetjmpTableSize, Value *&Label,
264 Value *&LongjmpResult, BasicBlock *&EndBB);
265 template <typename CallOrInvoke> Function *getInvokeWrapper(CallOrInvoke *CI);
266
267 bool areAllExceptionsAllowed() const { return EHWhitelistSet.empty(); }
268 bool canLongjmp(Module &M, const Value *Callee) const;
269 bool isEmAsmCall(Module &M, const Value *Callee) const;
270
271 void rebuildSSA(Function &F);
272
273public:
274 static char ID;
275
276 WebAssemblyLowerEmscriptenEHSjLj(bool EnableEH = true, bool EnableSjLj = true)
277 : ModulePass(ID), EnableEH(EnableEH), EnableSjLj(EnableSjLj) {
278 EHWhitelistSet.insert(EHWhitelist.begin(), EHWhitelist.end());
279 }
280 bool runOnModule(Module &M) override;
281
282 void getAnalysisUsage(AnalysisUsage &AU) const override {
283 AU.addRequired<DominatorTreeWrapperPass>();
284 }
285};
286} // End anonymous namespace
287
288char WebAssemblyLowerEmscriptenEHSjLj::ID = 0;
289INITIALIZE_PASS(WebAssemblyLowerEmscriptenEHSjLj, DEBUG_TYPE,static void *initializeWebAssemblyLowerEmscriptenEHSjLjPassOnce
(PassRegistry &Registry) { PassInfo *PI = new PassInfo( "WebAssembly Lower Emscripten Exceptions / Setjmp / Longjmp"
, "wasm-lower-em-ehsjlj", &WebAssemblyLowerEmscriptenEHSjLj
::ID, PassInfo::NormalCtor_t(callDefaultCtor<WebAssemblyLowerEmscriptenEHSjLj
>), false, false); Registry.registerPass(*PI, true); return
PI; } static llvm::once_flag InitializeWebAssemblyLowerEmscriptenEHSjLjPassFlag
; void llvm::initializeWebAssemblyLowerEmscriptenEHSjLjPass(PassRegistry
&Registry) { llvm::call_once(InitializeWebAssemblyLowerEmscriptenEHSjLjPassFlag
, initializeWebAssemblyLowerEmscriptenEHSjLjPassOnce, std::ref
(Registry)); }
290 "WebAssembly Lower Emscripten Exceptions / Setjmp / Longjmp",static void *initializeWebAssemblyLowerEmscriptenEHSjLjPassOnce
(PassRegistry &Registry) { PassInfo *PI = new PassInfo( "WebAssembly Lower Emscripten Exceptions / Setjmp / Longjmp"
, "wasm-lower-em-ehsjlj", &WebAssemblyLowerEmscriptenEHSjLj
::ID, PassInfo::NormalCtor_t(callDefaultCtor<WebAssemblyLowerEmscriptenEHSjLj
>), false, false); Registry.registerPass(*PI, true); return
PI; } static llvm::once_flag InitializeWebAssemblyLowerEmscriptenEHSjLjPassFlag
; void llvm::initializeWebAssemblyLowerEmscriptenEHSjLjPass(PassRegistry
&Registry) { llvm::call_once(InitializeWebAssemblyLowerEmscriptenEHSjLjPassFlag
, initializeWebAssemblyLowerEmscriptenEHSjLjPassOnce, std::ref
(Registry)); }
291 false, false)static void *initializeWebAssemblyLowerEmscriptenEHSjLjPassOnce
(PassRegistry &Registry) { PassInfo *PI = new PassInfo( "WebAssembly Lower Emscripten Exceptions / Setjmp / Longjmp"
, "wasm-lower-em-ehsjlj", &WebAssemblyLowerEmscriptenEHSjLj
::ID, PassInfo::NormalCtor_t(callDefaultCtor<WebAssemblyLowerEmscriptenEHSjLj
>), false, false); Registry.registerPass(*PI, true); return
PI; } static llvm::once_flag InitializeWebAssemblyLowerEmscriptenEHSjLjPassFlag
; void llvm::initializeWebAssemblyLowerEmscriptenEHSjLjPass(PassRegistry
&Registry) { llvm::call_once(InitializeWebAssemblyLowerEmscriptenEHSjLjPassFlag
, initializeWebAssemblyLowerEmscriptenEHSjLjPassOnce, std::ref
(Registry)); }
292
293ModulePass *llvm::createWebAssemblyLowerEmscriptenEHSjLj(bool EnableEH,
294 bool EnableSjLj) {
295 return new WebAssemblyLowerEmscriptenEHSjLj(EnableEH, EnableSjLj);
296}
297
298static bool canThrow(const Value *V) {
299 if (const auto *F = dyn_cast<const Function>(V)) {
300 // Intrinsics cannot throw
301 if (F->isIntrinsic())
302 return false;
303 StringRef Name = F->getName();
304 // leave setjmp and longjmp (mostly) alone, we process them properly later
305 if (Name == "setjmp" || Name == "longjmp")
306 return false;
307 return !F->doesNotThrow();
308 }
309 // not a function, so an indirect call - can throw, we can't tell
310 return true;
311}
312
313// Get a global variable with the given name. If it doesn't exist declare it,
314// which will generate an import and asssumes that it will exist at link time.
315static GlobalVariable *getGlobalVariableI32(Module &M, IRBuilder<> &IRB,
316 const char *Name) {
317
318 auto *GV =
319 dyn_cast<GlobalVariable>(M.getOrInsertGlobal(Name, IRB.getInt32Ty()));
320 if (!GV)
321 report_fatal_error(Twine("unable to create global: ") + Name);
322
323 return GV;
324}
325
326// Simple function name mangler.
327// This function simply takes LLVM's string representation of parameter types
328// and concatenate them with '_'. There are non-alphanumeric characters but llc
329// is ok with it, and we need to postprocess these names after the lowering
330// phase anyway.
331static std::string getSignature(FunctionType *FTy) {
332 std::string Sig;
333 raw_string_ostream OS(Sig);
334 OS << *FTy->getReturnType();
26
Called C++ object pointer is null
335 for (Type *ParamTy : FTy->params())
336 OS << "_" << *ParamTy;
337 if (FTy->isVarArg())
338 OS << "_...";
339 Sig = OS.str();
340 Sig.erase(remove_if(Sig, isspace), Sig.end());
341 // When s2wasm parses .s file, a comma means the end of an argument. So a
342 // mangled function name can contain any character but a comma.
343 std::replace(Sig.begin(), Sig.end(), ',', '.');
344 return Sig;
345}
346
347// Returns __cxa_find_matching_catch_N function, where N = NumClauses + 2.
348// This is because a landingpad instruction contains two more arguments, a
349// personality function and a cleanup bit, and __cxa_find_matching_catch_N
350// functions are named after the number of arguments in the original landingpad
351// instruction.
352Function *
353WebAssemblyLowerEmscriptenEHSjLj::getFindMatchingCatch(Module &M,
354 unsigned NumClauses) {
355 if (FindMatchingCatches.count(NumClauses))
356 return FindMatchingCatches[NumClauses];
357 PointerType *Int8PtrTy = Type::getInt8PtrTy(M.getContext());
358 SmallVector<Type *, 16> Args(NumClauses, Int8PtrTy);
359 FunctionType *FTy = FunctionType::get(Int8PtrTy, Args, false);
360 Function *F = Function::Create(
361 FTy, GlobalValue::ExternalLinkage,
362 "__cxa_find_matching_catch_" + Twine(NumClauses + 2), &M);
363 FindMatchingCatches[NumClauses] = F;
364 return F;
365}
366
367// Generate invoke wrapper seqence with preamble and postamble
368// Preamble:
369// __THREW__ = 0;
370// Postamble:
371// %__THREW__.val = __THREW__; __THREW__ = 0;
372// Returns %__THREW__.val, which indicates whether an exception is thrown (or
373// whether longjmp occurred), for future use.
374template <typename CallOrInvoke>
375Value *WebAssemblyLowerEmscriptenEHSjLj::wrapInvoke(CallOrInvoke *CI) {
376 LLVMContext &C = CI->getModule()->getContext();
377
378 // If we are calling a function that is noreturn, we must remove that
379 // attribute. The code we insert here does expect it to return, after we
380 // catch the exception.
381 if (CI->doesNotReturn()) {
17
Taking false branch
382 if (auto *F = dyn_cast<Function>(CI->getCalledValue()))
383 F->removeFnAttr(Attribute::NoReturn);
384 CI->removeAttribute(AttributeList::FunctionIndex, Attribute::NoReturn);
385 }
386
387 IRBuilder<> IRB(C);
388 IRB.SetInsertPoint(CI);
389
390 // Pre-invoke
391 // __THREW__ = 0;
392 IRB.CreateStore(IRB.getInt32(0), ThrewGV);
393
394 // Invoke function wrapper in JavaScript
395 SmallVector<Value *, 16> Args;
396 // Put the pointer to the callee as first argument, so it can be called
397 // within the invoke wrapper later
398 Args.push_back(CI->getCalledValue());
399 Args.append(CI->arg_begin(), CI->arg_end());
400 CallInst *NewCall = IRB.CreateCall(getInvokeWrapper(CI), Args);
18
Calling 'WebAssemblyLowerEmscriptenEHSjLj::getInvokeWrapper'
401 NewCall->takeName(CI);
402 NewCall->setCallingConv(CallingConv::WASM_EmscriptenInvoke);
403 NewCall->setDebugLoc(CI->getDebugLoc());
404
405 // Because we added the pointer to the callee as first argument, all
406 // argument attribute indices have to be incremented by one.
407 SmallVector<AttributeSet, 8> ArgAttributes;
408 const AttributeList &InvokeAL = CI->getAttributes();
409
410 // No attributes for the callee pointer.
411 ArgAttributes.push_back(AttributeSet());
412 // Copy the argument attributes from the original
413 for (unsigned I = 0, E = CI->getNumArgOperands(); I < E; ++I)
414 ArgAttributes.push_back(InvokeAL.getParamAttributes(I));
415
416 AttrBuilder FnAttrs(InvokeAL.getFnAttributes());
417 if (FnAttrs.contains(Attribute::AllocSize)) {
418 // The allocsize attribute (if any) referes to parameters by index and needs
419 // to be adjusted.
420 unsigned SizeArg;
421 Optional<unsigned> NEltArg;
422 std::tie(SizeArg, NEltArg) = FnAttrs.getAllocSizeArgs();
423 SizeArg += 1;
424 if (NEltArg.hasValue())
425 NEltArg = NEltArg.getValue() + 1;
426 FnAttrs.addAllocSizeAttr(SizeArg, NEltArg);
427 }
428
429 // Reconstruct the AttributesList based on the vector we constructed.
430 AttributeList NewCallAL =
431 AttributeList::get(C, AttributeSet::get(C, FnAttrs),
432 InvokeAL.getRetAttributes(), ArgAttributes);
433 NewCall->setAttributes(NewCallAL);
434
435 CI->replaceAllUsesWith(NewCall);
436
437 // Post-invoke
438 // %__THREW__.val = __THREW__; __THREW__ = 0;
439 Value *Threw =
440 IRB.CreateLoad(IRB.getInt32Ty(), ThrewGV, ThrewGV->getName() + ".val");
441 IRB.CreateStore(IRB.getInt32(0), ThrewGV);
442 return Threw;
443}
444
445// Get matching invoke wrapper based on callee signature
446template <typename CallOrInvoke>
447Function *WebAssemblyLowerEmscriptenEHSjLj::getInvokeWrapper(CallOrInvoke *CI) {
448 Module *M = CI->getModule();
449 SmallVector<Type *, 16> ArgTys;
450 Value *Callee = CI->getCalledValue();
451 FunctionType *CalleeFTy;
452 if (auto *F
19.1
'F' is null
= dyn_cast<Function>(Callee))
19
Assuming 'Callee' is not a 'Function'
20
Taking false branch
453 CalleeFTy = F->getFunctionType();
454 else {
455 auto *CalleeTy = cast<PointerType>(Callee->getType())->getElementType();
21
The object is a 'PointerType'
456 CalleeFTy = dyn_cast<FunctionType>(CalleeTy);
22
Assuming 'CalleeTy' is not a 'FunctionType'
23
Null pointer value stored to 'CalleeFTy'
457 }
458
459 std::string Sig = getSignature(CalleeFTy);
24
Passing null pointer value via 1st parameter 'FTy'
25
Calling 'getSignature'
460 if (InvokeWrappers.find(Sig) != InvokeWrappers.end())
461 return InvokeWrappers[Sig];
462
463 // Put the pointer to the callee as first argument
464 ArgTys.push_back(PointerType::getUnqual(CalleeFTy));
465 // Add argument types
466 ArgTys.append(CalleeFTy->param_begin(), CalleeFTy->param_end());
467
468 FunctionType *FTy = FunctionType::get(CalleeFTy->getReturnType(), ArgTys,
469 CalleeFTy->isVarArg());
470 Function *F =
471 Function::Create(FTy, GlobalValue::ExternalLinkage, "__invoke_" + Sig, M);
472 InvokeWrappers[Sig] = F;
473 return F;
474}
475
476bool WebAssemblyLowerEmscriptenEHSjLj::canLongjmp(Module &M,
477 const Value *Callee) const {
478 if (auto *CalleeF = dyn_cast<Function>(Callee))
479 if (CalleeF->isIntrinsic())
480 return false;
481
482 // Attempting to transform inline assembly will result in something like:
483 // call void @__invoke_void(void ()* asm ...)
484 // which is invalid because inline assembly blocks do not have addresses
485 // and can't be passed by pointer. The result is a crash with illegal IR.
486 if (isa<InlineAsm>(Callee))
487 return false;
488 StringRef CalleeName = Callee->getName();
489
490 // The reason we include malloc/free here is to exclude the malloc/free
491 // calls generated in setjmp prep / cleanup routines.
492 if (CalleeName == "setjmp" || CalleeName == "malloc" || CalleeName == "free")
493 return false;
494
495 // There are functions in JS glue code
496 if (CalleeName == "__resumeException" || CalleeName == "llvm_eh_typeid_for" ||
497 CalleeName == "saveSetjmp" || CalleeName == "testSetjmp" ||
498 CalleeName == "getTempRet0" || CalleeName == "setTempRet0")
499 return false;
500
501 // __cxa_find_matching_catch_N functions cannot longjmp
502 if (Callee->getName().startswith("__cxa_find_matching_catch_"))
503 return false;
504
505 // Exception-catching related functions
506 if (CalleeName == "__cxa_begin_catch" || CalleeName == "__cxa_end_catch" ||
507 CalleeName == "__cxa_allocate_exception" || CalleeName == "__cxa_throw" ||
508 CalleeName == "__clang_call_terminate")
509 return false;
510
511 // Otherwise we don't know
512 return true;
513}
514
515bool WebAssemblyLowerEmscriptenEHSjLj::isEmAsmCall(Module &M,
516 const Value *Callee) const {
517 StringRef CalleeName = Callee->getName();
518 // This is an exhaustive list from Emscripten's <emscripten/em_asm.h>.
519 return CalleeName == "emscripten_asm_const_int" ||
520 CalleeName == "emscripten_asm_const_double" ||
521 CalleeName == "emscripten_asm_const_int_sync_on_main_thread" ||
522 CalleeName == "emscripten_asm_const_double_sync_on_main_thread" ||
523 CalleeName == "emscripten_asm_const_async_on_main_thread";
524}
525
526// Generate testSetjmp function call seqence with preamble and postamble.
527// The code this generates is equivalent to the following JavaScript code:
528// if (%__THREW__.val != 0 & threwValue != 0) {
529// %label = _testSetjmp(mem[%__THREW__.val], setjmpTable, setjmpTableSize);
530// if (%label == 0)
531// emscripten_longjmp(%__THREW__.val, threwValue);
532// setTempRet0(threwValue);
533// } else {
534// %label = -1;
535// }
536// %longjmp_result = getTempRet0();
537//
538// As output parameters. returns %label, %longjmp_result, and the BB the last
539// instruction (%longjmp_result = ...) is in.
540void WebAssemblyLowerEmscriptenEHSjLj::wrapTestSetjmp(
541 BasicBlock *BB, Instruction *InsertPt, Value *Threw, Value *SetjmpTable,
542 Value *SetjmpTableSize, Value *&Label, Value *&LongjmpResult,
543 BasicBlock *&EndBB) {
544 Function *F = BB->getParent();
545 LLVMContext &C = BB->getModule()->getContext();
546 IRBuilder<> IRB(C);
547 IRB.SetInsertPoint(InsertPt);
548
549 // if (%__THREW__.val != 0 & threwValue != 0)
550 IRB.SetInsertPoint(BB);
551 BasicBlock *ThenBB1 = BasicBlock::Create(C, "if.then1", F);
552 BasicBlock *ElseBB1 = BasicBlock::Create(C, "if.else1", F);
553 BasicBlock *EndBB1 = BasicBlock::Create(C, "if.end", F);
554 Value *ThrewCmp = IRB.CreateICmpNE(Threw, IRB.getInt32(0));
555 Value *ThrewValue = IRB.CreateLoad(IRB.getInt32Ty(), ThrewValueGV,
556 ThrewValueGV->getName() + ".val");
557 Value *ThrewValueCmp = IRB.CreateICmpNE(ThrewValue, IRB.getInt32(0));
558 Value *Cmp1 = IRB.CreateAnd(ThrewCmp, ThrewValueCmp, "cmp1");
559 IRB.CreateCondBr(Cmp1, ThenBB1, ElseBB1);
560
561 // %label = _testSetjmp(mem[%__THREW__.val], _setjmpTable, _setjmpTableSize);
562 // if (%label == 0)
563 IRB.SetInsertPoint(ThenBB1);
564 BasicBlock *ThenBB2 = BasicBlock::Create(C, "if.then2", F);
565 BasicBlock *EndBB2 = BasicBlock::Create(C, "if.end2", F);
566 Value *ThrewInt = IRB.CreateIntToPtr(Threw, Type::getInt32PtrTy(C),
567 Threw->getName() + ".i32p");
568 Value *LoadedThrew = IRB.CreateLoad(IRB.getInt32Ty(), ThrewInt,
569 ThrewInt->getName() + ".loaded");
570 Value *ThenLabel = IRB.CreateCall(
571 TestSetjmpF, {LoadedThrew, SetjmpTable, SetjmpTableSize}, "label");
572 Value *Cmp2 = IRB.CreateICmpEQ(ThenLabel, IRB.getInt32(0));
573 IRB.CreateCondBr(Cmp2, ThenBB2, EndBB2);
574
575 // emscripten_longjmp(%__THREW__.val, threwValue);
576 IRB.SetInsertPoint(ThenBB2);
577 IRB.CreateCall(EmLongjmpF, {Threw, ThrewValue});
578 IRB.CreateUnreachable();
579
580 // setTempRet0(threwValue);
581 IRB.SetInsertPoint(EndBB2);
582 IRB.CreateCall(SetTempRet0Func, ThrewValue);
583 IRB.CreateBr(EndBB1);
584
585 IRB.SetInsertPoint(ElseBB1);
586 IRB.CreateBr(EndBB1);
587
588 // longjmp_result = getTempRet0();
589 IRB.SetInsertPoint(EndBB1);
590 PHINode *LabelPHI = IRB.CreatePHI(IRB.getInt32Ty(), 2, "label");
591 LabelPHI->addIncoming(ThenLabel, EndBB2);
592
593 LabelPHI->addIncoming(IRB.getInt32(-1), ElseBB1);
594
595 // Output parameter assignment
596 Label = LabelPHI;
597 EndBB = EndBB1;
598 LongjmpResult = IRB.CreateCall(GetTempRet0Func, None, "longjmp_result");
599}
600
601void WebAssemblyLowerEmscriptenEHSjLj::rebuildSSA(Function &F) {
602 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
603 DT.recalculate(F); // CFG has been changed
604 SSAUpdater SSA;
605 for (BasicBlock &BB : F) {
606 for (Instruction &I : BB) {
607 SSA.Initialize(I.getType(), I.getName());
608 SSA.AddAvailableValue(&BB, &I);
609 for (auto UI = I.use_begin(), UE = I.use_end(); UI != UE;) {
610 Use &U = *UI;
611 ++UI;
612 auto *User = cast<Instruction>(U.getUser());
613 if (auto *UserPN = dyn_cast<PHINode>(User))
614 if (UserPN->getIncomingBlock(U) == &BB)
615 continue;
616
617 if (DT.dominates(&I, User))
618 continue;
619 SSA.RewriteUseAfterInsertions(U);
620 }
621 }
622 }
623}
624
625bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
626 LLVM_DEBUG(dbgs() << "********** Lower Emscripten EH & SjLj **********\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("wasm-lower-em-ehsjlj")) { dbgs() << "********** Lower Emscripten EH & SjLj **********\n"
; } } while (false)
;
1
Assuming 'DebugFlag' is false
2
Loop condition is false. Exiting loop
627
628 LLVMContext &C = M.getContext();
629 IRBuilder<> IRB(C);
630
631 Function *SetjmpF = M.getFunction("setjmp");
632 Function *LongjmpF = M.getFunction("longjmp");
633 bool SetjmpUsed = SetjmpF && !SetjmpF->use_empty();
3
Assuming 'SetjmpF' is null
634 bool LongjmpUsed = LongjmpF && !LongjmpF->use_empty();
4
Assuming 'LongjmpF' is null
635 bool DoSjLj = EnableSjLj && (SetjmpUsed || LongjmpUsed);
5
Assuming field 'EnableSjLj' is false
636
637 // Declare (or get) global variables __THREW__, __threwValue, and
638 // getTempRet0/setTempRet0 function which are used in common for both
639 // exception handling and setjmp/longjmp handling
640 ThrewGV = getGlobalVariableI32(M, IRB, "__THREW__");
641 ThrewValueGV = getGlobalVariableI32(M, IRB, "__threwValue");
642 GetTempRet0Func =
643 Function::Create(FunctionType::get(IRB.getInt32Ty(), false),
644 GlobalValue::ExternalLinkage, "getTempRet0", &M);
645 SetTempRet0Func = Function::Create(
646 FunctionType::get(IRB.getVoidTy(), IRB.getInt32Ty(), false),
647 GlobalValue::ExternalLinkage, "setTempRet0", &M);
648 GetTempRet0Func->setDoesNotThrow();
649 SetTempRet0Func->setDoesNotThrow();
650
651 bool Changed = false;
652
653 // Exception handling
654 if (EnableEH) {
6
Assuming field 'EnableEH' is true
7
Taking true branch
655 // Register __resumeException function
656 FunctionType *ResumeFTy =
657 FunctionType::get(IRB.getVoidTy(), IRB.getInt8PtrTy(), false);
658 ResumeF = Function::Create(ResumeFTy, GlobalValue::ExternalLinkage,
659 "__resumeException", &M);
660
661 // Register llvm_eh_typeid_for function
662 FunctionType *EHTypeIDTy =
663 FunctionType::get(IRB.getInt32Ty(), IRB.getInt8PtrTy(), false);
664 EHTypeIDF = Function::Create(EHTypeIDTy, GlobalValue::ExternalLinkage,
665 "llvm_eh_typeid_for", &M);
666
667 for (Function &F : M) {
668 if (F.isDeclaration())
8
Assuming the condition is false
9
Taking false branch
669 continue;
670 Changed |= runEHOnFunction(F);
10
Calling 'WebAssemblyLowerEmscriptenEHSjLj::runEHOnFunction'
671 }
672 }
673
674 // Setjmp/longjmp handling
675 if (DoSjLj) {
676 Changed = true; // We have setjmp or longjmp somewhere
677
678 if (LongjmpF) {
679 // Replace all uses of longjmp with emscripten_longjmp_jmpbuf, which is
680 // defined in JS code
681 EmLongjmpJmpbufF = Function::Create(LongjmpF->getFunctionType(),
682 GlobalValue::ExternalLinkage,
683 "emscripten_longjmp_jmpbuf", &M);
684
685 LongjmpF->replaceAllUsesWith(EmLongjmpJmpbufF);
686 }
687
688 if (SetjmpF) {
689 // Register saveSetjmp function
690 FunctionType *SetjmpFTy = SetjmpF->getFunctionType();
691 SmallVector<Type *, 4> Params = {SetjmpFTy->getParamType(0),
692 IRB.getInt32Ty(), Type::getInt32PtrTy(C),
693 IRB.getInt32Ty()};
694 FunctionType *FTy =
695 FunctionType::get(Type::getInt32PtrTy(C), Params, false);
696 SaveSetjmpF =
697 Function::Create(FTy, GlobalValue::ExternalLinkage, "saveSetjmp", &M);
698
699 // Register testSetjmp function
700 Params = {IRB.getInt32Ty(), Type::getInt32PtrTy(C), IRB.getInt32Ty()};
701 FTy = FunctionType::get(IRB.getInt32Ty(), Params, false);
702 TestSetjmpF =
703 Function::Create(FTy, GlobalValue::ExternalLinkage, "testSetjmp", &M);
704
705 FTy = FunctionType::get(IRB.getVoidTy(),
706 {IRB.getInt32Ty(), IRB.getInt32Ty()}, false);
707 EmLongjmpF = Function::Create(FTy, GlobalValue::ExternalLinkage,
708 "emscripten_longjmp", &M);
709
710 // Only traverse functions that uses setjmp in order not to insert
711 // unnecessary prep / cleanup code in every function
712 SmallPtrSet<Function *, 8> SetjmpUsers;
713 for (User *U : SetjmpF->users()) {
714 auto *UI = cast<Instruction>(U);
715 SetjmpUsers.insert(UI->getFunction());
716 }
717 for (Function *F : SetjmpUsers)
718 runSjLjOnFunction(*F);
719 }
720 }
721
722 if (!Changed) {
723 // Delete unused global variables and functions
724 if (ResumeF)
725 ResumeF->eraseFromParent();
726 if (EHTypeIDF)
727 EHTypeIDF->eraseFromParent();
728 if (EmLongjmpF)
729 EmLongjmpF->eraseFromParent();
730 if (SaveSetjmpF)
731 SaveSetjmpF->eraseFromParent();
732 if (TestSetjmpF)
733 TestSetjmpF->eraseFromParent();
734 return false;
735 }
736
737 return true;
738}
739
740bool WebAssemblyLowerEmscriptenEHSjLj::runEHOnFunction(Function &F) {
741 Module &M = *F.getParent();
742 LLVMContext &C = F.getContext();
743 IRBuilder<> IRB(C);
744 bool Changed = false;
745 SmallVector<Instruction *, 64> ToErase;
746 SmallPtrSet<LandingPadInst *, 32> LandingPads;
747 bool AllowExceptions =
748 areAllExceptionsAllowed() || EHWhitelistSet.count(F.getName());
11
Assuming the condition is false
749
750 for (BasicBlock &BB : F) {
751 auto *II = dyn_cast<InvokeInst>(BB.getTerminator());
12
Assuming the object is a 'InvokeInst'
752 if (!II
12.1
'II' is non-null
)
13
Taking false branch
753 continue;
754 LandingPads.insert(II->getLandingPadInst());
755 IRB.SetInsertPoint(II);
756
757 bool NeedInvoke = AllowExceptions && canThrow(II->getCalledValue());
14
Assuming 'AllowExceptions' is true
758 if (NeedInvoke
14.1
'NeedInvoke' is true
) {
15
Taking true branch
759 // Wrap invoke with invoke wrapper and generate preamble/postamble
760 Value *Threw = wrapInvoke(II);
16
Calling 'WebAssemblyLowerEmscriptenEHSjLj::wrapInvoke'
761 ToErase.push_back(II);
762
763 // Insert a branch based on __THREW__ variable
764 Value *Cmp = IRB.CreateICmpEQ(Threw, IRB.getInt32(1), "cmp");
765 IRB.CreateCondBr(Cmp, II->getUnwindDest(), II->getNormalDest());
766
767 } else {
768 // This can't throw, and we don't need this invoke, just replace it with a
769 // call+branch
770 SmallVector<Value *, 16> Args(II->arg_begin(), II->arg_end());
771 CallInst *NewCall =
772 IRB.CreateCall(II->getFunctionType(), II->getCalledValue(), Args);
773 NewCall->takeName(II);
774 NewCall->setCallingConv(II->getCallingConv());
775 NewCall->setDebugLoc(II->getDebugLoc());
776 NewCall->setAttributes(II->getAttributes());
777 II->replaceAllUsesWith(NewCall);
778 ToErase.push_back(II);
779
780 IRB.CreateBr(II->getNormalDest());
781
782 // Remove any PHI node entries from the exception destination
783 II->getUnwindDest()->removePredecessor(&BB);
784 }
785 }
786
787 // Process resume instructions
788 for (BasicBlock &BB : F) {
789 // Scan the body of the basic block for resumes
790 for (Instruction &I : BB) {
791 auto *RI = dyn_cast<ResumeInst>(&I);
792 if (!RI)
793 continue;
794
795 // Split the input into legal values
796 Value *Input = RI->getValue();
797 IRB.SetInsertPoint(RI);
798 Value *Low = IRB.CreateExtractValue(Input, 0, "low");
799 // Create a call to __resumeException function
800 IRB.CreateCall(ResumeF, {Low});
801 // Add a terminator to the block
802 IRB.CreateUnreachable();
803 ToErase.push_back(RI);
804 }
805 }
806
807 // Process llvm.eh.typeid.for intrinsics
808 for (BasicBlock &BB : F) {
809 for (Instruction &I : BB) {
810 auto *CI = dyn_cast<CallInst>(&I);
811 if (!CI)
812 continue;
813 const Function *Callee = CI->getCalledFunction();
814 if (!Callee)
815 continue;
816 if (Callee->getIntrinsicID() != Intrinsic::eh_typeid_for)
817 continue;
818
819 IRB.SetInsertPoint(CI);
820 CallInst *NewCI =
821 IRB.CreateCall(EHTypeIDF, CI->getArgOperand(0), "typeid");
822 CI->replaceAllUsesWith(NewCI);
823 ToErase.push_back(CI);
824 }
825 }
826
827 // Look for orphan landingpads, can occur in blocks with no predecessors
828 for (BasicBlock &BB : F) {
829 Instruction *I = BB.getFirstNonPHI();
830 if (auto *LPI = dyn_cast<LandingPadInst>(I))
831 LandingPads.insert(LPI);
832 }
833 Changed = !LandingPads.empty();
834
835 // Handle all the landingpad for this function together, as multiple invokes
836 // may share a single lp
837 for (LandingPadInst *LPI : LandingPads) {
838 IRB.SetInsertPoint(LPI);
839 SmallVector<Value *, 16> FMCArgs;
840 for (unsigned I = 0, E = LPI->getNumClauses(); I < E; ++I) {
841 Constant *Clause = LPI->getClause(I);
842 // As a temporary workaround for the lack of aggregate varargs support
843 // in the interface between JS and wasm, break out filter operands into
844 // their component elements.
845 if (LPI->isFilter(I)) {
846 auto *ATy = cast<ArrayType>(Clause->getType());
847 for (unsigned J = 0, E = ATy->getNumElements(); J < E; ++J) {
848 Value *EV = IRB.CreateExtractValue(Clause, makeArrayRef(J), "filter");
849 FMCArgs.push_back(EV);
850 }
851 } else
852 FMCArgs.push_back(Clause);
853 }
854
855 // Create a call to __cxa_find_matching_catch_N function
856 Function *FMCF = getFindMatchingCatch(M, FMCArgs.size());
857 CallInst *FMCI = IRB.CreateCall(FMCF, FMCArgs, "fmc");
858 Value *Undef = UndefValue::get(LPI->getType());
859 Value *Pair0 = IRB.CreateInsertValue(Undef, FMCI, 0, "pair0");
860 Value *TempRet0 = IRB.CreateCall(GetTempRet0Func, None, "tempret0");
861 Value *Pair1 = IRB.CreateInsertValue(Pair0, TempRet0, 1, "pair1");
862
863 LPI->replaceAllUsesWith(Pair1);
864 ToErase.push_back(LPI);
865 }
866
867 // Erase everything we no longer need in this function
868 for (Instruction *I : ToErase)
869 I->eraseFromParent();
870
871 return Changed;
872}
873
874bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
875 Module &M = *F.getParent();
876 LLVMContext &C = F.getContext();
877 IRBuilder<> IRB(C);
878 SmallVector<Instruction *, 64> ToErase;
879 // Vector of %setjmpTable values
880 std::vector<Instruction *> SetjmpTableInsts;
881 // Vector of %setjmpTableSize values
882 std::vector<Instruction *> SetjmpTableSizeInsts;
883
884 // Setjmp preparation
885
886 // This instruction effectively means %setjmpTableSize = 4.
887 // We create this as an instruction intentionally, and we don't want to fold
888 // this instruction to a constant 4, because this value will be used in
889 // SSAUpdater.AddAvailableValue(...) later.
890 BasicBlock &EntryBB = F.getEntryBlock();
891 BinaryOperator *SetjmpTableSize = BinaryOperator::Create(
892 Instruction::Add, IRB.getInt32(4), IRB.getInt32(0), "setjmpTableSize",
893 &*EntryBB.getFirstInsertionPt());
894 // setjmpTable = (int *) malloc(40);
895 Instruction *SetjmpTable = CallInst::CreateMalloc(
896 SetjmpTableSize, IRB.getInt32Ty(), IRB.getInt32Ty(), IRB.getInt32(40),
897 nullptr, nullptr, "setjmpTable");
898 // setjmpTable[0] = 0;
899 IRB.SetInsertPoint(SetjmpTableSize);
900 IRB.CreateStore(IRB.getInt32(0), SetjmpTable);
901 SetjmpTableInsts.push_back(SetjmpTable);
902 SetjmpTableSizeInsts.push_back(SetjmpTableSize);
903
904 // Setjmp transformation
905 std::vector<PHINode *> SetjmpRetPHIs;
906 Function *SetjmpF = M.getFunction("setjmp");
907 for (User *U : SetjmpF->users()) {
908 auto *CI = dyn_cast<CallInst>(U);
909 if (!CI)
910 report_fatal_error("Does not support indirect calls to setjmp");
911
912 BasicBlock *BB = CI->getParent();
913 if (BB->getParent() != &F) // in other function
914 continue;
915
916 // The tail is everything right after the call, and will be reached once
917 // when setjmp is called, and later when longjmp returns to the setjmp
918 BasicBlock *Tail = SplitBlock(BB, CI->getNextNode());
919 // Add a phi to the tail, which will be the output of setjmp, which
920 // indicates if this is the first call or a longjmp back. The phi directly
921 // uses the right value based on where we arrive from
922 IRB.SetInsertPoint(Tail->getFirstNonPHI());
923 PHINode *SetjmpRet = IRB.CreatePHI(IRB.getInt32Ty(), 2, "setjmp.ret");
924
925 // setjmp initial call returns 0
926 SetjmpRet->addIncoming(IRB.getInt32(0), BB);
927 // The proper output is now this, not the setjmp call itself
928 CI->replaceAllUsesWith(SetjmpRet);
929 // longjmp returns to the setjmp will add themselves to this phi
930 SetjmpRetPHIs.push_back(SetjmpRet);
931
932 // Fix call target
933 // Our index in the function is our place in the array + 1 to avoid index
934 // 0, because index 0 means the longjmp is not ours to handle.
935 IRB.SetInsertPoint(CI);
936 Value *Args[] = {CI->getArgOperand(0), IRB.getInt32(SetjmpRetPHIs.size()),
937 SetjmpTable, SetjmpTableSize};
938 Instruction *NewSetjmpTable =
939 IRB.CreateCall(SaveSetjmpF, Args, "setjmpTable");
940 Instruction *NewSetjmpTableSize =
941 IRB.CreateCall(GetTempRet0Func, None, "setjmpTableSize");
942 SetjmpTableInsts.push_back(NewSetjmpTable);
943 SetjmpTableSizeInsts.push_back(NewSetjmpTableSize);
944 ToErase.push_back(CI);
945 }
946
947 // Update each call that can longjmp so it can return to a setjmp where
948 // relevant.
949
950 // Because we are creating new BBs while processing and don't want to make
951 // all these newly created BBs candidates again for longjmp processing, we
952 // first make the vector of candidate BBs.
953 std::vector<BasicBlock *> BBs;
954 for (BasicBlock &BB : F)
955 BBs.push_back(&BB);
956
957 // BBs.size() will change within the loop, so we query it every time
958 for (unsigned I = 0; I < BBs.size(); I++) {
959 BasicBlock *BB = BBs[I];
960 for (Instruction &I : *BB) {
961 assert(!isa<InvokeInst>(&I))((!isa<InvokeInst>(&I)) ? static_cast<void> (
0) : __assert_fail ("!isa<InvokeInst>(&I)", "/build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp"
, 961, __PRETTY_FUNCTION__))
;
962 auto *CI = dyn_cast<CallInst>(&I);
963 if (!CI)
964 continue;
965
966 const Value *Callee = CI->getCalledValue();
967 if (!canLongjmp(M, Callee))
968 continue;
969 if (isEmAsmCall(M, Callee))
970 report_fatal_error("Cannot use EM_ASM* alongside setjmp/longjmp in " +
971 F.getName() +
972 ". Please consider using EM_JS, or move the "
973 "EM_ASM into another function.",
974 false);
975
976 Value *Threw = nullptr;
977 BasicBlock *Tail;
978 if (Callee->getName().startswith("__invoke_")) {
979 // If invoke wrapper has already been generated for this call in
980 // previous EH phase, search for the load instruction
981 // %__THREW__.val = __THREW__;
982 // in postamble after the invoke wrapper call
983 LoadInst *ThrewLI = nullptr;
984 StoreInst *ThrewResetSI = nullptr;
985 for (auto I = std::next(BasicBlock::iterator(CI)), IE = BB->end();
986 I != IE; ++I) {
987 if (auto *LI = dyn_cast<LoadInst>(I))
988 if (auto *GV = dyn_cast<GlobalVariable>(LI->getPointerOperand()))
989 if (GV == ThrewGV) {
990 Threw = ThrewLI = LI;
991 break;
992 }
993 }
994 // Search for the store instruction after the load above
995 // __THREW__ = 0;
996 for (auto I = std::next(BasicBlock::iterator(ThrewLI)), IE = BB->end();
997 I != IE; ++I) {
998 if (auto *SI = dyn_cast<StoreInst>(I))
999 if (auto *GV = dyn_cast<GlobalVariable>(SI->getPointerOperand()))
1000 if (GV == ThrewGV && SI->getValueOperand() == IRB.getInt32(0)) {
1001 ThrewResetSI = SI;
1002 break;
1003 }
1004 }
1005 assert(Threw && ThrewLI && "Cannot find __THREW__ load after invoke")((Threw && ThrewLI && "Cannot find __THREW__ load after invoke"
) ? static_cast<void> (0) : __assert_fail ("Threw && ThrewLI && \"Cannot find __THREW__ load after invoke\""
, "/build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp"
, 1005, __PRETTY_FUNCTION__))
;
1006 assert(ThrewResetSI && "Cannot find __THREW__ store after invoke")((ThrewResetSI && "Cannot find __THREW__ store after invoke"
) ? static_cast<void> (0) : __assert_fail ("ThrewResetSI && \"Cannot find __THREW__ store after invoke\""
, "/build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp"
, 1006, __PRETTY_FUNCTION__))
;
1007 Tail = SplitBlock(BB, ThrewResetSI->getNextNode());
1008
1009 } else {
1010 // Wrap call with invoke wrapper and generate preamble/postamble
1011 Threw = wrapInvoke(CI);
1012 ToErase.push_back(CI);
1013 Tail = SplitBlock(BB, CI->getNextNode());
1014 }
1015
1016 // We need to replace the terminator in Tail - SplitBlock makes BB go
1017 // straight to Tail, we need to check if a longjmp occurred, and go to the
1018 // right setjmp-tail if so
1019 ToErase.push_back(BB->getTerminator());
1020
1021 // Generate a function call to testSetjmp function and preamble/postamble
1022 // code to figure out (1) whether longjmp occurred (2) if longjmp
1023 // occurred, which setjmp it corresponds to
1024 Value *Label = nullptr;
1025 Value *LongjmpResult = nullptr;
1026 BasicBlock *EndBB = nullptr;
1027 wrapTestSetjmp(BB, CI, Threw, SetjmpTable, SetjmpTableSize, Label,
1028 LongjmpResult, EndBB);
1029 assert(Label && LongjmpResult && EndBB)((Label && LongjmpResult && EndBB) ? static_cast
<void> (0) : __assert_fail ("Label && LongjmpResult && EndBB"
, "/build/llvm-toolchain-snapshot-10~++20200107111111+051c4d5b7bc/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp"
, 1029, __PRETTY_FUNCTION__))
;
1030
1031 // Create switch instruction
1032 IRB.SetInsertPoint(EndBB);
1033 SwitchInst *SI = IRB.CreateSwitch(Label, Tail, SetjmpRetPHIs.size());
1034 // -1 means no longjmp happened, continue normally (will hit the default
1035 // switch case). 0 means a longjmp that is not ours to handle, needs a
1036 // rethrow. Otherwise the index is the same as the index in P+1 (to avoid
1037 // 0).
1038 for (unsigned I = 0; I < SetjmpRetPHIs.size(); I++) {
1039 SI->addCase(IRB.getInt32(I + 1), SetjmpRetPHIs[I]->getParent());
1040 SetjmpRetPHIs[I]->addIncoming(LongjmpResult, EndBB);
1041 }
1042
1043 // We are splitting the block here, and must continue to find other calls
1044 // in the block - which is now split. so continue to traverse in the Tail
1045 BBs.push_back(Tail);
1046 }
1047 }
1048
1049 // Erase everything we no longer need in this function
1050 for (Instruction *I : ToErase)
1051 I->eraseFromParent();
1052
1053 // Free setjmpTable buffer before each return instruction
1054 for (BasicBlock &BB : F) {
1055 Instruction *TI = BB.getTerminator();
1056 if (isa<ReturnInst>(TI))
1057 CallInst::CreateFree(SetjmpTable, TI);
1058 }
1059
1060 // Every call to saveSetjmp can change setjmpTable and setjmpTableSize
1061 // (when buffer reallocation occurs)
1062 // entry:
1063 // setjmpTableSize = 4;
1064 // setjmpTable = (int *) malloc(40);
1065 // setjmpTable[0] = 0;
1066 // ...
1067 // somebb:
1068 // setjmpTable = saveSetjmp(buf, label, setjmpTable, setjmpTableSize);
1069 // setjmpTableSize = getTempRet0();
1070 // So we need to make sure the SSA for these variables is valid so that every
1071 // saveSetjmp and testSetjmp calls have the correct arguments.
1072 SSAUpdater SetjmpTableSSA;
1073 SSAUpdater SetjmpTableSizeSSA;
1074 SetjmpTableSSA.Initialize(Type::getInt32PtrTy(C), "setjmpTable");
1075 SetjmpTableSizeSSA.Initialize(Type::getInt32Ty(C), "setjmpTableSize");
1076 for (Instruction *I : SetjmpTableInsts)
1077 SetjmpTableSSA.AddAvailableValue(I->getParent(), I);
1078 for (Instruction *I : SetjmpTableSizeInsts)
1079 SetjmpTableSizeSSA.AddAvailableValue(I->getParent(), I);
1080
1081 for (auto UI = SetjmpTable->use_begin(), UE = SetjmpTable->use_end();
1082 UI != UE;) {
1083 // Grab the use before incrementing the iterator.
1084 Use &U = *UI;
1085 // Increment the iterator before removing the use from the list.
1086 ++UI;
1087 if (auto *I = dyn_cast<Instruction>(U.getUser()))
1088 if (I->getParent() != &EntryBB)
1089 SetjmpTableSSA.RewriteUse(U);
1090 }
1091 for (auto UI = SetjmpTableSize->use_begin(), UE = SetjmpTableSize->use_end();
1092 UI != UE;) {
1093 Use &U = *UI;
1094 ++UI;
1095 if (auto *I = dyn_cast<Instruction>(U.getUser()))
1096 if (I->getParent() != &EntryBB)
1097 SetjmpTableSizeSSA.RewriteUse(U);
1098 }
1099
1100 // Finally, our modifications to the cfg can break dominance of SSA variables.
1101 // For example, in this code,
1102 // if (x()) { .. setjmp() .. }
1103 // if (y()) { .. longjmp() .. }
1104 // We must split the longjmp block, and it can jump into the block splitted
1105 // from setjmp one. But that means that when we split the setjmp block, it's
1106 // first part no longer dominates its second part - there is a theoretically
1107 // possible control flow path where x() is false, then y() is true and we
1108 // reach the second part of the setjmp block, without ever reaching the first
1109 // part. So, we rebuild SSA form here.
1110 rebuildSSA(F);
1111 return true;
1112}