[asm.js] Test and fix function name collisions.

R=ahaas@chromium.org
TEST=message/asm-function-variable-collision
BUG=v8:6127

Change-Id: I75658f0bf58a8b3de5eb42f4f054476f8d2c139b
Reviewed-on: https://chromium-review.googlesource.com/469651
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44475}

src/asmjs/asm-parser.cc

@@ -741,9 +741,12 @@ void AsmJsParser::ValidateFunction() {
     function_info->kind = VarKind::kFunction;
     function_info->function_builder = module_builder_->AddFunction();
     function_info->index = function_info->function_builder->func_index();
+  } else if (function_info->kind != VarKind::kFunction) {
+    FAIL("Function name collides with variable");
   } else if (function_info->function_defined) {
     FAIL("Function redefined");
   }
+
   function_info->function_defined = true;
   // TODO(bradnelson): Cleanup memory management here.
   // WasmModuleBuilder should own these.
@@ -806,9 +809,6 @@ void AsmJsParser::ValidateFunction() {
     function_info->index = current_function_builder_->func_index();
     function_info->type = function_type;
   } else {
-    if (function_info->kind != VarKind::kFunction) {
-      FAIL("Function name collides with variable");
-    }
     // TODO(bradnelson): Should IsExactly be used here?
     if (!function_info->type->IsA(AsmType::None()) &&
         !function_type->IsA(function_info->type)) {

test/message/asm-function-redefined.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --validate-asm --no-stress-opt --no-stress-validate-asm --no-suppress-asm-messages --fast-validate-asm
+
+// Violates asm.js because symbol {f} is defined as module function twice.
+
+function Module() {
+  "use asm"
+  function f() {}
+  function f() {}
+  return { f:f };
+}
+Module().f();

test/message/asm-function-redefined.out

+# Copyright 2017 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+*%(basename)s:12: Invalid asm.js: Function redefined

test/message/asm-function-variable-collision.js

+// Copyright 2017 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --validate-asm --no-stress-opt --no-stress-validate-asm --no-suppress-asm-messages --fast-validate-asm
+
+// Violates asm.js because symbol {f} is used as module variable and function.
+
+function Module() {
+  "use asm"
+  var f = 0;
+  function f() {}
+  return { f:f };
+}
+Module();

test/message/asm-function-variable-collision.out

+# Copyright 2017 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+*%(basename)s:12: Invalid asm.js: Function name collides with variable