[WebAssembly] ensure .functype applies to right label in assembler

We used to require .functype immediately follows the label it sets the type of, but not all Clang output follows this rule.

Now we simply allow it on any symbol, but only assume its a function start for a defined symbol, which is simpler and more general.

Fixes (part of) https://bugs.llvm.org/show_bug.cgi?id=49036

Differential Revision: https://reviews.llvm.org/D96165

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

@@ -203,7 +203,6 @@ class WebAssemblyAsmParser final : public MCTargetAsmParser {
   // guarantee that correct order.
   enum ParserState {
     FileStart,
-    Label,
     FunctionStart,
     FunctionLocals,
     Instructions,
@@ -223,9 +222,6 @@ class WebAssemblyAsmParser final : public MCTargetAsmParser {
   };
   std::vector<NestingType> NestingStack;
 
-  // We track this to see if a .functype following a label is the same,
-  // as this is how we recognize the start of a function.
-  MCSymbol *LastLabel = nullptr;
   MCSymbol *LastFunctionLabel = nullptr;
 
 public:
@@ -687,11 +683,6 @@ class WebAssemblyAsmParser final : public MCTargetAsmParser {
     return false;
   }
 
-  void onLabelParsed(MCSymbol *Symbol) override {
-    LastLabel = Symbol;
-    CurrentState = Label;
-  }
-
   bool parseSignature(wasm::WasmSignature *Signature) {
     if (expect(AsmToken::LParen, "("))
       return true;
@@ -808,12 +799,12 @@ class WebAssemblyAsmParser final : public MCTargetAsmParser {
       if (SymName.empty())
         return true;
       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
-      if (CurrentState == Label && WasmSym == LastLabel) {
+      if (WasmSym->isDefined()) {
         // This .functype indicates a start of a function.
         if (ensureEmptyNestingStack())
           return true;
         CurrentState = FunctionStart;
-        LastFunctionLabel = LastLabel;
+        LastFunctionLabel = WasmSym;
         push(Function);
       }
       auto Signature = std::make_unique<wasm::WasmSignature>();
@@ -881,7 +872,7 @@ class WebAssemblyAsmParser final : public MCTargetAsmParser {
 
     if (DirectiveID.getString() == ".local") {
       if (CurrentState != FunctionStart)
-        return error(".local directive should follow the start of a function",
+        return error(".local directive should follow the start of a function: ",
                      Lexer.getTok());
       SmallVector<wasm::ValType, 4> Locals;
       if (parseRegTypeList(Locals))

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

@@ -8,6 +8,8 @@ empty_func:
     end_function
 
 test0:
+# local labels can appear between label and its .functype.
+.Ltest0begin:
     # Test all types:
     .functype   test0 (i32, i64) -> (i32)
     .eventtype  __cpp_exception i32
@@ -116,17 +118,18 @@ test0:
     .globaltype __stack_pointer, i32
 
 .tabletype empty_eref_table, externref
-empty_eref_table:       
+empty_eref_table:
 
 .tabletype empty_fref_table, funcref
-empty_fref_table:       
+empty_fref_table:
+
 
-
 # CHECK:           .text
 # CHECK-LABEL: empty_func:
 # CHECK-NEXT:      .functype	empty_func () -> ()
 # CHECK-NEXT:      end_function
 # CHECK-LABEL: test0:
+# CHECK-NEXT:  .Ltest0begin:
 # CHECK-NEXT:      .functype   test0 (i32, i64) -> (i32)
 # CHECK-NEXT:      .eventtype  __cpp_exception i32
 # CHECK-NEXT:      .local      f32, f64
@@ -226,6 +229,6 @@ empty_fref_table:
 
 # CHECK:           .tabletype empty_eref_table, externref
 # CHECK-NEXT: empty_eref_table:
-        
+
 # CHECK:           .tabletype empty_fref_table, funcref
 # CHECK-NEXT: empty_fref_table: