Revert "[wasm] Re-exported globals preserve their identity"

This reverts commit f7a1932e.

Reason for revert: Breaking wasm wpt tests: https://ci.chromium.org/p/v8/builders/ci/V8%20Blink%20Linux/5408

Original change's description:
> [wasm] Re-exported globals preserve their identity
> 
> V8 fails a recently added spec test that when an imported global get
> re-exported, it should preserve its identity. This CL fixes the behavior
> in V8.
> 
> Drive-by change: fix the object printer of globals: a global which
> stores a reference type only has a tagged buffer, a global which stores
> a value type only has an untagged buffer.
> 
> R=​clemensb@chromium.org
> 
> Bug: v8:10556
> Change-Id: I949d147fe4395610cfec6cf60082e1faecb23036
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2235702
> Commit-Queue: Andreas Haas <ahaas@chromium.org>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#68513}

TBR=ahaas@chromium.org,clemensb@chromium.org

Change-Id: I06eb1996cafe7d4e93a7e59d21679fea239cf961
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10556
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2264956Reviewed-by: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68528}

src/diagnostics/objects-printer.cc

@@ -1815,11 +1815,8 @@ void WasmTableObject::WasmTableObjectPrint(std::ostream& os) {  // NOLINT
 
 void WasmGlobalObject::WasmGlobalObjectPrint(std::ostream& os) {  // NOLINT
   PrintHeader(os, "WasmGlobalObject");
-  if (type().is_reference_type()) {
-    os << "\n - tagged_buffer: " << Brief(tagged_buffer());
-  } else {
-    os << "\n - untagged_buffer: " << Brief(untagged_buffer());
-  }
+  os << "\n - untagged_buffer: " << Brief(untagged_buffer());
+  os << "\n - tagged_buffer: " << Brief(tagged_buffer());
   os << "\n - offset: " << offset();
   os << "\n - raw_type: " << raw_type();
   os << "\n - is_mutable: " << is_mutable();

src/wasm/module-instantiate.cc

@@ -259,6 +259,9 @@ class InstanceBuilder {
   // Process initialization of globals.
   void InitGlobals(Handle<WasmInstanceObject> instance);
 
+
+  bool NeedsWrappers() const;
+
   // Process the exports, creating wrappers for functions, tables, memories,
   // and globals.
   void ProcessExports(Handle<WasmInstanceObject> instance);
@@ -1476,29 +1479,31 @@ bool InstanceBuilder::AllocateMemory() {
   return true;
 }
 
+bool InstanceBuilder::NeedsWrappers() const {
+  if (module_->num_exported_functions > 0) return true;
+  for (auto& table : module_->tables) {
+    if (table.type.heap_type() == kHeapFunc) return true;
+  }
+  return false;
+}
+
 // Process the exports, creating wrappers for functions, tables, memories,
 // globals, and exceptions.
 void InstanceBuilder::ProcessExports(Handle<WasmInstanceObject> instance) {
-  std::unordered_map<int, Handle<Object>> imported_globals;
-
-  // If an imported WebAssembly function or global gets exported, the export
-  // has to be identical to to import. Therefore we cache all imported
-  // WebAssembly functions in the instance, and all imported globals in a map
-  // here.
-  for (int index = 0, end = static_cast<int>(module_->import_table.size());
-       index < end; ++index) {
-    const WasmImport& import = module_->import_table[index];
-    if (import.kind == kExternalFunction) {
-      Handle<Object> value = sanitized_imports_[index].value;
-      if (WasmExternalFunction::IsWasmExternalFunction(*value)) {
-        WasmInstanceObject::SetWasmExternalFunction(
-            isolate_, instance, import.index,
-            Handle<WasmExternalFunction>::cast(value));
-      }
-    } else if (import.kind == kExternalGlobal) {
-      Handle<Object> value = sanitized_imports_[index].value;
-      if (value->IsWasmGlobalObject()) {
-        imported_globals[import.index] = value;
+  if (NeedsWrappers()) {
+    // If an imported WebAssembly function gets exported, the exported function
+    // has to be identical to to imported function. Therefore we cache all
+    // imported WebAssembly functions in the instance.
+    for (int index = 0, end = static_cast<int>(module_->import_table.size());
+         index < end; ++index) {
+      const WasmImport& import = module_->import_table[index];
+      if (import.kind == kExternalFunction) {
+        Handle<Object> value = sanitized_imports_[index].value;
+        if (WasmExternalFunction::IsWasmExternalFunction(*value)) {
+          WasmInstanceObject::SetWasmExternalFunction(
+              isolate_, instance, import.index,
+              Handle<WasmExternalFunction>::cast(value));
+        }
       }
     }
   }
@@ -1558,13 +1563,6 @@ void InstanceBuilder::ProcessExports(Handle<WasmInstanceObject> instance) {
       }
       case kExternalGlobal: {
         const WasmGlobal& global = module_->globals[exp.index];
-        if (global.imported) {
-          auto cached_global = imported_globals.find(exp.index);
-          if (cached_global != imported_globals.end()) {
-            desc.set_value(cached_global->second);
-            break;
-          }
-        }
         Handle<JSArrayBuffer> untagged_buffer;
         Handle<FixedArray> tagged_buffer;
         uint32_t offset;

test/mjsunit/wasm/globals-import-export-identity.js

-// Copyright 2020 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.
-
-load('test/mjsunit/wasm/wasm-module-builder.js');
-
-const global1 = new WebAssembly.Global({value: 'i32', mutable: true}, 14);
-const global2 = new WebAssembly.Global({value: 'i32', mutable: true}, 15);
-const global3 = new WebAssembly.Global({value: 'i32', mutable: true}, 32);
-
-const builder = new WasmModuleBuilder();
-
-// Two additional globals, so that global-index != export-index.
-builder.addImportedGlobal('module', 'global1', kWasmI32, true);
-builder.addImportedGlobal('module', 'global2', kWasmI32, true);
-const globalIndex =
-    builder.addImportedGlobal('module', 'global3', kWasmI32, true);
-builder.addExportOfKind('exportedGlobal', kExternalGlobal, globalIndex);
-
-const buffer = builder.toBuffer();
-
-const module = new WebAssembly.Module(buffer);
-const instance = new WebAssembly.Instance(module, {
-  'module': {
-    'global1': global1,
-    'global2': global2,
-    'global3': global3,
-  }
-});
-
-assertEquals(global3, instance.exports.exportedGlobal);

test/wasm-js/wasm-js.status

@@ -7,6 +7,7 @@
 [ALWAYS, {
   # TODO(v8:10556): Remove sub-typing in the reference-types implementation
   'constructor/instantiate': [FAIL],
+  'instance/constructor-caching': [FAIL],
   'instance/constructor': [FAIL],
   'proposals/js-types/constructor/instantiate': [FAIL],
   'proposals/js-types/global/constructor': [FAIL],