[Wasm Exceptions] Assertion on "Active sort region list not finished"

[kripken]

Full error:

clang++: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyCFGSort.cpp:330: void sortBlocks(llvm::MachineFunction &, const llvm::MachineLoopInfo &, const llvm::WebAssemblyExceptionInfo &, const llvm::MachineDominatorTree &): Assertion `Entries.empty() && "Active sort region list not finished"' failed.

Testcase:

int main() {
  try {
    try {
      throw 0;
    } catch (int) {
    }
  } catch (int) {
  }
}

STR: ./em++ a.cpp -c -fwasm-exceptions on #13485 (where this was found, using tot from right now, sdk-releases-upstream-0fcee855ada6358c4fe6e8c2a7f291c54cde4876-64bit).

[kripken]

Btw @aheejin I think I saw while reducing this that the testcases could alternate between this error and either #13514 or #13515. Makes me wonder if maybe there's an underlying single cause perhaps? But I'm not 100% sure I saw that. I can check tomorrow if the information would be useful.