Reject lack of "use asm" marker in asm typer.

Until now we've been allowing unmarked asm code
through the typer. Start rejecting it.

Adding a cctest that asm modules missing an export return
fail validation.

BUG= https://code.google.com/p/v8/issues/detail?id=4203
TEST=test-asm-validator
R=aseemgarg@chromium.org,titzer@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1569423002

Cr-Commit-Position: refs/heads/master@{#33199}

src/typing-asm.cc

@@ -76,6 +76,13 @@ void AsmTyper::VisitAsmModule(FunctionLiteral* fun) {
   Scope* scope = fun->scope();
   if (!scope->is_function_scope()) FAIL(fun, "not at function scope");
 
+  ExpressionStatement* use_asm = fun->body()->first()->AsExpressionStatement();
+  if (use_asm == NULL) FAIL(fun, "missing \"use asm\"");
+  Literal* use_asm_literal = use_asm->expression()->AsLiteral();
+  if (use_asm_literal == NULL) FAIL(fun, "missing \"use asm\"");
+  if (!use_asm_literal->raw_value()->AsString()->IsOneByteEqualTo("use asm"))
+    FAIL(fun, "missing \"use asm\"");
+
   // Module parameters.
   for (int i = 0; i < scope->num_parameters(); ++i) {
     Variable* param = scope->parameter(i);

test/cctest/test-asm-validator.cc

@@ -309,6 +309,52 @@ TEST(ValidateMinimum) {
 }
 
 
+TEST(MissingUseAsm) {
+  const char test_function[] =
+      "function foo() {\n"
+      "  function bar() {}\n"
+      "  return { bar: bar };\n"
+      "}\n";
+  v8::V8::Initialize();
+  HandleAndZoneScope handles;
+  Zone* zone = handles.main_zone();
+  ZoneVector<ExpressionTypeEntry> types(zone);
+  CHECK_EQ("asm: line 1: missing \"use asm\"\n",
+           Validate(zone, test_function, &types));
+}
+
+
+TEST(WrongUseAsm) {
+  const char test_function[] =
+      "function foo() {\n"
+      "  \"use wasm\"\n"
+      "  function bar() {}\n"
+      "  return { bar: bar };\n"
+      "}\n";
+  v8::V8::Initialize();
+  HandleAndZoneScope handles;
+  Zone* zone = handles.main_zone();
+  ZoneVector<ExpressionTypeEntry> types(zone);
+  CHECK_EQ("asm: line 1: missing \"use asm\"\n",
+           Validate(zone, test_function, &types));
+}
+
+
+TEST(MissingReturnExports) {
+  const char test_function[] =
+      "function foo() {\n"
+      "  \"use asm\"\n"
+      "  function bar() {}\n"
+      "}\n";
+  v8::V8::Initialize();
+  HandleAndZoneScope handles;
+  Zone* zone = handles.main_zone();
+  ZoneVector<ExpressionTypeEntry> types(zone);
+  CHECK_EQ("asm: line 2: last statement in module is not a return\n",
+           Validate(zone, test_function, &types));
+}
+
+
 #define HARNESS_STDLIB()                 \
   "var Infinity = stdlib.Infinity;\n"    \
   "var NaN = stdlib.NaN;\n"              \