[WebAssembly] Make SjLj lowering globals thread-local

Emscripten's longjump and exception mechanism depends on two global variables,
`__THREW__` and `__threwValue`, which are changed to be defined as thread-local
in emscripten-core/emscripten#12056. This patch updates
the corresponding code in the WebAssembly backend to properly declare these
globals as thread-local as well.

Differential Revision: https://reviews.llvm.org/D88262

Author: tlively

llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp

@@ -315,9 +315,12 @@ static bool canThrow(const Value *V) {
 // which will generate an import and asssumes that it will exist at link time.
 static GlobalVariable *getGlobalVariableI32(Module &M, IRBuilder<> &IRB,
                                             const char *Name) {
-
-  auto *GV =
-      dyn_cast<GlobalVariable>(M.getOrInsertGlobal(Name, IRB.getInt32Ty()));
+  auto Int32Ty = IRB.getInt32Ty();
+  auto *GV = dyn_cast<GlobalVariable>(M.getOrInsertGlobal(Name, Int32Ty, [&]() {
+    return new GlobalVariable(M, Int32Ty, false,
+                              GlobalVariable::ExternalLinkage, nullptr, Name,
+                              nullptr, GlobalValue::LocalExecTLSModel);
+  }));
   if (!GV)
     report_fatal_error(Twine("unable to create global: ") + Name);
 

llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp

@@ -348,12 +348,6 @@ FunctionPass *WebAssemblyPassConfig::createTargetRegisterAllocator(bool) {
 //===----------------------------------------------------------------------===//
 
 void WebAssemblyPassConfig::addIRPasses() {
-  // Runs LowerAtomicPass if necessary
-  addPass(new CoalesceFeaturesAndStripAtomics(&getWebAssemblyTargetMachine()));
-
-  // This is a no-op if atomics are not used in the module
-  addPass(createAtomicExpandPass());
-
   // Add signatures to prototype-less function declarations
   addPass(createWebAssemblyAddMissingPrototypes());
 
@@ -389,6 +383,12 @@ void WebAssemblyPassConfig::addIRPasses() {
   // Expand indirectbr instructions to switches.
   addPass(createIndirectBrExpandPass());
 
+  // Lower atomics and TLS if necessary
+  addPass(new CoalesceFeaturesAndStripAtomics(&getWebAssemblyTargetMachine()));
+
+  // This is a no-op if atomics are not used in the module
+  addPass(createAtomicExpandPass());
+
   TargetPassConfig::addIRPasses();
 }
 

llvm/test/CodeGen/WebAssembly/lower-em-exceptions.ll

@@ -5,8 +5,8 @@ target triple = "wasm32-unknown-unknown"
 
 @_ZTIi = external constant i8*
 @_ZTIc = external constant i8*
-; CHECK-DAG: __THREW__ = external global i32
-; CHECK-DAG: __threwValue = external global i32
+; CHECK-DAG: __THREW__ = external thread_local(localexec) global i32
+; CHECK-DAG: __threwValue = external thread_local(localexec) global i32
 
 ; Test invoke instruction with clauses (try-catch block)
 define void @clause() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {

llvm/test/CodeGen/WebAssembly/lower-em-sjlj.ll

@@ -6,8 +6,8 @@ target triple = "wasm32-unknown-unknown"
 %struct.__jmp_buf_tag = type { [6 x i32], i32, [32 x i32] }
 
 @global_var = global i32 0, align 4
-; CHECK-DAG: __THREW__ = external global i32
-; CHECK-DAG: __threwValue = external global i32
+; CHECK-DAG: __THREW__ = external thread_local(localexec) global i32
+; CHECK-DAG: __threwValue = external thread_local(localexec) global i32
 
 ; Test a simple setjmp - longjmp sequence
 define void @setjmp_longjmp() {