Handle __asm declaration in base text

Accept `__asm` to output assembly code directly
not only in function, but also in base text.

String only, no argument (register specifier) allowed.

src/cc/arch/aarch64/emit_code.c

@@ -588,6 +588,11 @@ static void emit_defun(Function *func) {
   // Static variables are emitted through global variables.
 }
 
+static void emit_asm(Expr *asmstr) {
+  assert(asmstr->kind == EX_STR);
+  EMIT_ASM(asmstr->str.buf);
+}
+
 void emit_code(Vector *decls) {
   for (int i = 0, len = decls->len; i < len; ++i) {
     Declaration *decl = decls->data[i];
@@ -600,6 +605,9 @@ void emit_code(Vector *decls) {
       break;
     case DCL_VARDECL:
       break;
+    case DCL_ASM:
+      emit_asm(decl->asmstr);
+      break;
     }
   }
 

src/cc/arch/x64/emit_code.c

@@ -578,6 +578,11 @@ static void emit_defun(Function *func) {
   // Static variables are emitted through global variables.
 }
 
+static void emit_asm(Expr *asmstr) {
+  assert(asmstr->kind == EX_STR);
+  EMIT_ASM(asmstr->str.buf);
+}
+
 void emit_code(Vector *decls) {
   for (int i = 0, len = decls->len; i < len; ++i) {
     Declaration *decl = decls->data[i];
@@ -590,6 +595,9 @@ void emit_code(Vector *decls) {
       break;
     case DCL_VARDECL:
       break;
+    case DCL_ASM:
+      emit_asm(decl->asmstr);
+      break;
     }
   }
 

src/cc/backend/codegen.c

@@ -951,6 +951,8 @@ static void gen_decl(Declaration *decl) {
     break;
   case DCL_VARDECL:
     break;
+  case DCL_ASM:
+    break;
   }
 }
 

src/cc/frontend/ast.c

@@ -335,6 +335,12 @@ Declaration *new_decl_vardecl(Vector *decls) {
   return decl;
 }
 
+Declaration *new_decl_asm(Expr *str) {
+  Declaration *decl = new_decl(DCL_ASM);
+  decl->asmstr = str;
+  return decl;
+}
+
 // ================================================
 
 // Function

src/cc/frontend/ast.h

@@ -480,6 +480,7 @@ Function *new_func(Type *type, const Name *name, const Vector *params, int flag)
 enum DeclKind {
   DCL_DEFUN,
   DCL_VARDECL,
+  DCL_ASM,
 };
 
 typedef struct Declaration {
@@ -491,8 +492,10 @@ typedef struct Declaration {
     struct {
       Vector *decls;  // <VarDecl*>
     } vardecl;
+    Expr *asmstr;
   };
 } Declaration;
 
 Declaration *new_decl_defun(Function *func);
 Declaration *new_decl_vardecl(Vector *decls);
+Declaration *new_decl_asm(Expr *str);

src/cc/frontend/parser.c

@@ -766,6 +766,14 @@ static Declaration *parse_global_var_decl(Type *rawtype, int storage, Type *type
 }
 
 static Declaration *parse_declaration(void) {
+  Token *tok;
+  if ((tok = match(TK_ASM)) != NULL) {
+    Stmt *asm_ = parse_asm(tok);
+    if (asm_->asm_.arg != NULL)
+      parse_error(PE_NOFATAL, asm_->token, "no argument required");
+    return new_decl_asm(asm_->asm_.str);
+  }
+
   Type *rawtype = NULL;
   int storage;
   Token *ident;

src/wcc/gen_wasm.c

@@ -1690,6 +1690,9 @@ static void gen_decl(Declaration *decl) {
     break;
   case DCL_VARDECL:
     break;
+  case DCL_ASM:
+    assert(false);
+    break;
   }
 }
 

src/wcc/traverse.c

@@ -692,6 +692,9 @@ static void traverse_decl(Declaration *decl) {
     break;
   case DCL_VARDECL:
     break;
+  case DCL_ASM:
+    parse_error(PE_NOFATAL, decl->asmstr->token, "`__asm` not allowed");
+    break;
   }
 }