[WebAssembly] Forbid use of EM_ASM with setjmp/longjmp

[quantum]

Summary

We tried to support EM_ASM with setjmp/longjmp in binaryen. But with dynamic
linking thrown into the mix, the code is no longer understandable and cannot
be maintained. We also discovered more bugs in the EM_ASM handling code.

To ensure maintainability and correctness of the binaryen code, EM_ASM will
no longer be supported with setjmp/longjmp. This is probably fine since the
support was added recently and haven't be published.

[kripken]

lgtm module the error message, let's find the best phrasing there.

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

1005

How about "alongside" instead of "with", to hint that the issue is using both in the same function?

And/or maybe replace the final "." with ", or refactor the EM_ASM to another function"?

[tlively]

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

550

Where does this list of functions come from? How do we know it's exhaustive?

554

Maybe use std::any_of over an array of the function names as plain strings to reduce repetition?

[quantum]

Address review comments.

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

550

Stated that the list is exhaustive and link the header where these functions came from.

554

This is the style used in this file, so we are doing it for consistency.

1005

Done.

[sbc100]

llvm/trunk/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

555 ↗

(On Diff #215644)

Why not just compare names here?

[quantum]

llvm/trunk/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

555 ↗

(On Diff #215644)

For consistency with WebAssemblyLowerEmscriptenEHSjLj::canLongjmp.

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

class WebAssemblyLowerEmscriptenEHSjLj final : public ModulePass {
   template <typename CallOrInvoke> Value *wrapInvoke(CallOrInvoke *CI);
   void wrapTestSetjmp(BasicBlock *BB, Instruction *InsertPt, Value *Threw,
                       Value *SetjmpTable, Value *SetjmpTableSize, Value *&Label,
                       Value *&LongjmpResult, BasicBlock *&EndBB);
   template <typename CallOrInvoke> Function *getInvokeWrapper(CallOrInvoke *CI);
 
   bool areAllExceptionsAllowed() const { return EHWhitelistSet.empty(); }
   bool canLongjmp(Module &M, const Value *Callee) const;
+  bool isEmAsmCall(Module &M, const Value *Callee) const;
 
   void rebuildSSA(Function &F);
 
 public:
   static char ID;
 
   WebAssemblyLowerEmscriptenEHSjLj(bool EnableEH = true, bool EnableSjLj = true)
       : ModulePass(ID), EnableEH(EnableEH), EnableSjLj(EnableSjLj) {
if (Callee == BeginCatchF || Callee == EndCatchF ||
       Callee == AllocExceptionF || Callee == ThrowF || Callee == TerminateF ||
       Callee == GetTempRet0Func || Callee == SetTempRet0Func)
     return false;
 
   // Otherwise we don't know
   return true;
 }
 
+bool WebAssemblyLowerEmscriptenEHSjLj::isEmAsmCall(Module &M,
+                                                   const Value *Callee) const {
+  // This is an exhaustive list from Emscripten's <emscripten/em_asm.h>.
+  Function *EmAsmConstIntF = M.getFunction("emscripten_asm_const_int");
+  Function *EmAsmConstDoubleF = M.getFunction("emscripten_asm_const_double");
+  Function *EmAsmConstIntSyncMainF =
+      M.getFunction("emscripten_asm_const_int_sync_on_main_thread");
+  Function *EmAsmConstDoubleSyncMainF =
+      M.getFunction("emscripten_asm_const_double_sync_on_main_thread");
+  Function *EmAsmConstAsyncMainF =
+      M.getFunction("emscripten_asm_const_async_on_main_thread");
+
+  return Callee == EmAsmConstIntF || Callee == EmAsmConstDoubleF ||
+         Callee == EmAsmConstIntSyncMainF ||
+         Callee == EmAsmConstDoubleSyncMainF || Callee == EmAsmConstAsyncMainF;
+}
+
 // Generate testSetjmp function call seqence with preamble and postamble.
 // The code this generates is equivalent to the following JavaScript code:
 // if (%__THREW__.val != 0 & threwValue != 0) {
 //   %label = _testSetjmp(mem[%__THREW__.val], setjmpTable, setjmpTableSize);
 //   if (%label == 0)
 //     emscripten_longjmp(%__THREW__.val, threwValue);
 //   setTempRet0(threwValue);
 // } else {
for (Instruction &I : *BB) {
       assert(!isa<InvokeInst>(&I));
       auto *CI = dyn_cast<CallInst>(&I);
       if (!CI)
         continue;
 
       const Value *Callee = CI->getCalledValue();
       if (!canLongjmp(M, Callee))
         continue;
+      if (isEmAsmCall(M, Callee))
+        report_fatal_error("Cannot use EM_ASM* alongside setjmp/longjmp in " +
+                               F.getName() +
+                               ". Please consider using EM_JS, or move the "
+                               "EM_ASM into another function.",
+                           false);
 
       Value *Threw = nullptr;
       BasicBlock *Tail;
       if (Callee->getName().startswith(InvokePrefix)) {
         // If invoke wrapper has already been generated for this call in
         // previous EH phase, search for the load instruction
         // %__THREW__.val = __THREW__;
         // in postamble after the invoke wrapper call