[torque] explicit definitions for contextual variables

Shared library sharing of template-defined global variables is broken on
Windows. This prepares contextual variables to export their globals from
a DLL.

Change-Id: I3092a92db71c4e516218081b97335d451d90bfe2
Reviewed-on: https://chromium-review.googlesource.com/1148049Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54628}

BUILD.gn

@@ -3182,10 +3182,12 @@ if (current_toolchain == v8_snapshot_toolchain) {
       "src/torque/implementation-visitor.h",
       "src/torque/scope.cc",
       "src/torque/scope.h",
+      "src/torque/source-positions.cc",
       "src/torque/source-positions.h",
       "src/torque/torque-parser.cc",
       "src/torque/torque-parser.h",
       "src/torque/torque.cc",
+      "src/torque/type-oracle.cc",
       "src/torque/type-oracle.h",
       "src/torque/types.cc",
       "src/torque/types.h",

src/torque/contextual.h

@@ -27,6 +27,8 @@ namespace torque {
 template <class Derived, class VarType>
 class ContextualVariable {
  public:
+  using VariableType = VarType;
+
   // A {Scope} contains a new object of type {VarType} and gives
   // ContextualVariable::Get() access to it. Upon destruction, the contextual
   // variable is restored to the state before the {Scope} was created. Scopes
@@ -67,14 +69,16 @@ class ContextualVariable {
   static thread_local VarType* top_;
 };
 
-template <class Derived, class VarType>
-thread_local VarType* ContextualVariable<Derived, VarType>::top_ = nullptr;
-
 // Usage: DECLARE_CONTEXTUAL_VARIABLE(VarName, VarType)
 #define DECLARE_CONTEXTUAL_VARIABLE(VarName, ...) \
   struct VarName                                  \
       : v8::internal::torque::ContextualVariable<VarName, __VA_ARGS__> {};
 
+#define DEFINE_CONTEXTUAL_VARIABLE(VarName) \
+  template <>                               \
+  thread_local VarName::VariableType*       \
+      ContextualVariable<VarName, VarName::VariableType>::top_ = nullptr;
+
 // By inheriting from {ContextualClass} a class can become a contextual variable
 // of itself, which is very similar to a singleton.
 template <class T>

src/torque/source-positions.cc

+// Copyright 2018 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.
+
+#include "src/torque/source-positions.h"
+
+namespace v8 {
+namespace internal {
+namespace torque {
+
+DEFINE_CONTEXTUAL_VARIABLE(CurrentSourceFile)
+DEFINE_CONTEXTUAL_VARIABLE(CurrentSourcePosition)
+DEFINE_CONTEXTUAL_VARIABLE(SourceFileMap)
+
+}  // namespace torque
+}  // namespace internal
+}  // namespace v8

src/torque/torque-parser.cc

@@ -12,6 +12,8 @@ namespace v8 {
 namespace internal {
 namespace torque {
 
+DEFINE_CONTEXTUAL_VARIABLE(CurrentAst);
+
 using TypeList = std::vector<TypeExpression*>;
 using GenericParameters = std::vector<std::string>;
 

src/torque/type-oracle.cc

+// Copyright 2018 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.
+
+#include "src/torque/type-oracle.h"
+
+namespace v8 {
+namespace internal {
+namespace torque {
+
+DEFINE_CONTEXTUAL_VARIABLE(TypeOracle)
+
+}  // namespace torque
+}  // namespace internal
+}  // namespace v8