[WebAssembly] Allow Wasm EH with Emscripten SjLj

[aheejin]

Summary

We explicitly made it error out in D101403, out of a good intention that
the error message will make people less confusing. Turns out, we weren't
failing all cases of wasm EH + SjLj; only a few cases were failing and
our client was able to get around by fixing source code, but now we made
it fail for all cases, even the cases that previously succeeded fail,
which we didn't intend. This reverts that change.

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
   auto &TM = TPC->getTM<WebAssemblyTargetMachine>();
 
   if ((EnableEH || DoSjLj) &&
       Triple(M.getTargetTriple()).getArch() == Triple::wasm64)
     report_fatal_error("Emscripten EH/SjLj is not supported with wasm64 yet");
   if (EnableEH && TM.Options.ExceptionModel == ExceptionHandling::Wasm)
     report_fatal_error("-exception-model=wasm not allowed with "
                        "-enable-emscripten-cxx-exceptions");
-  if (DoSjLj && TM.Options.ExceptionModel == ExceptionHandling::Wasm)
-    report_fatal_error("Emscripten SjLj is not supported with Wasm EH yet");
 
   // Declare (or get) global variables __THREW__, __threwValue, and
   // getTempRet0/setTempRet0 function which are used in common for both
   // exception handling and setjmp/longjmp handling
   ThrewGV = getGlobalVariableI32(M, IRB, TM, "__THREW__");
   ThrewValueGV = getGlobalVariableI32(M, IRB, TM, "__threwValue");
   GetTempRet0Func = getEmscriptenFunction(
       FunctionType::get(IRB.getInt32Ty(), false), "getTempRet0", &M);

llvm/test/CodeGen/WebAssembly/lower-em-ehsjlj-options.ll

 ; RUN: llc < %s -enable-emscripten-cxx-exceptions | FileCheck %s --check-prefix=EH
 ; RUN: llc < %s -enable-emscripten-sjlj | FileCheck %s --check-prefix=SJLJ
 ; RUN: llc < %s | FileCheck %s --check-prefix=NONE
 ; RUN: not --crash llc < %s -enable-emscripten-cxx-exceptions -mtriple=wasm64-unknown-unknown 2>&1 | FileCheck %s --check-prefix=WASM64-EH
 ; RUN: not --crash llc < %s -enable-emscripten-sjlj -mtriple=wasm64-unknown-unknown 2>&1 | FileCheck %s --check-prefix=WASM64-SJLJ
 ; RUN: not --crash llc < %s -enable-emscripten-cxx-exceptions -exception-model=wasm 2>&1 | FileCheck %s --check-prefix=WASM-EH-EM-EH
-; RUN: not --crash llc < %s -enable-emscripten-sjlj -exception-model=wasm 2>&1 | FileCheck %s --check-prefix=WASM-EH-EM-SJLJ
 
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32-unknown-unknown"
 
 %struct.__jmp_buf_tag = type { [6 x i32], i32, [32 x i32] }
 
 define void @exception() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
 ; EH-LABEL:   type exception,@function

 ; SJLJ: .import_name  emscripten_longjmp, emscripten_longjmp
 ; SJLJ-NOT: .functype  emscripten_longjmp_jmpbuf
 ; SJLJ-NOT: .import_module  emscripten_longjmp_jmpbuf
 ; SJLJ-NOT: .import_name  emscripten_longjmp_jmpbuf
 
 ; WASM64-EH: LLVM ERROR: Emscripten EH/SjLj is not supported with wasm64 yet
 ; WASM64-SJLJ: LLVM ERROR: Emscripten EH/SjLj is not supported with wasm64 yet
 ; WASM-EH-EM-EH: LLVM ERROR: -exception-model=wasm not allowed with -enable-emscripten-cxx-exceptions
-; WASM-EH-EM-SJLJ: LLVM ERROR: Emscripten SjLj is not supported with Wasm EH yet