[clang] [llvm] [WebAssembly] Implement an alternative translation for -wasm-enable-sjlj (PR #84137)

[YAMAMOTO Takashi via cfe-commits]

================
@@ -999,25 +1017,43 @@ bool WebAssemblyLowerEmscriptenEHSjLj::runOnModule(Module &M) {
       // Register __wasm_longjmp function, which calls __builtin_wasm_longjmp.
       FunctionType *FTy = FunctionType::get(
           IRB.getVoidTy(), {Int8PtrTy, IRB.getInt32Ty()}, false);
-      WasmLongjmpF = getEmscriptenFunction(FTy, "__wasm_longjmp", &M);
+      if (EnableWasmAltSjLj) {
+        WasmLongjmpF = getEmscriptenFunction(FTy, "__wasm_sjlj_longjmp", &M);
----------------
yamt wrote:

i wanted to have a common prefix for this set of api. (`__wasm_sjlj_`)

what's your suggestion for `testSetjmp`?
```
        saveSetjmp     -> __wasm_setjmp?
        testSetjmp     -> ???
        getTempRet0    -> (removed)
        __wasm_longjmp -> keep it
```


https://github.com/llvm/llvm-project/pull/84137