[WebAssembly] Add type checking for 'throw' (#108641)

This was previously missing.

Author: aheejin

llvm/lib/Target/WebAssembly/AsmParser/WebAssemblyAsmTypeCheck.cpp

@@ -420,6 +420,13 @@ bool WebAssemblyAsmTypeCheck::typeCheck(SMLoc ErrorLoc, const MCInst &Inst,
     if (popRefType(ErrorLoc))
       return true;
     Stack.push_back(wasm::ValType::I32);
+  } else if (Name == "throw") {
+    const wasm::WasmSignature *Sig = nullptr;
+    if (getSignature(Operands[1]->getStartLoc(), Inst.getOperand(0),
+                     wasm::WASM_SYMBOL_TYPE_TAG, Sig))
+      return true;
+    if (checkSig(ErrorLoc, *Sig))
+      return true;
   } else {
     // The current instruction is a stack instruction which doesn't have
     // explicit operands that indicate push/pop types, so we get those from

llvm/test/MC/WebAssembly/eh-assembly.s

@@ -10,6 +10,7 @@
 eh_legacy_test:
   # try-catch with catch, catch_all, throw, and rethrow
   try
+    i32.const 3
     throw     __cpp_exception
   catch       __cpp_exception
     drop
@@ -40,6 +41,7 @@ eh_legacy_test:
 
 # CHECK-LABEL: eh_legacy_test:
 # CHECK-NEXT:    try
+# CHECK-NEXT:    i32.const       3
 # CHECK-NEXT:    throw           __cpp_exception
 # CHECK-NEXT:    catch           __cpp_exception
 # CHECK-NEXT:    drop