Add ast::Variable::BindingPoint

Use this to simplify a bunch of code in semantic::Function.

Change-Id: Ia3f8a270ec576660eab00bcfa4df9a96138bd31e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/46261
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>

src/ast/variable.cc

@@ -45,6 +45,19 @@ Variable::Variable(Variable&&) = default;
 
 Variable::~Variable() = default;
 
+Variable::BindingPoint Variable::binding_point() const {
+  GroupDecoration* group = nullptr;
+  BindingDecoration* binding = nullptr;
+  for (auto* deco : decorations()) {
+    if (auto* g = deco->As<GroupDecoration>()) {
+      group = g;
+    } else if (auto* b = deco->As<BindingDecoration>()) {
+      binding = b;
+    }
+  }
+  return BindingPoint{group, binding};
+}
+
 bool Variable::HasLocationDecoration() const {
   for (auto* deco : decorations_) {
     if (deco->Is<LocationDecoration>()) {

src/ast/variable.h

@@ -25,6 +25,8 @@
 namespace tint {
 namespace ast {
 
+class BindingDecoration;
+class GroupDecoration;
 class LocationDecoration;
 
 /// A Variable statement.
@@ -76,6 +78,18 @@ class LocationDecoration;
 /// The storage class for a formal parameter is always StorageClass::kNone.
 class Variable : public Castable<Variable, Node> {
  public:
+  /// BindingPoint holds a group and binding decoration.
+  struct BindingPoint {
+    /// The `[[group]]` part of the binding point
+    GroupDecoration* group = nullptr;
+    /// The `[[binding]]` part of the binding point
+    BindingDecoration* binding = nullptr;
+
+    /// @returns true if the BindingPoint has a valid group and binding
+    /// decoration.
+    inline operator bool() const { return group && binding; }
+  };
+
   /// Create a variable
   /// @param source the variable source
   /// @param sym the variable symbol
@@ -117,6 +131,9 @@ class Variable : public Castable<Variable, Node> {
   /// @returns the decorations attached to this variable
   const DecorationList& decorations() const { return decorations_; }
 
+  /// @returns the binding point information for the variable
+  BindingPoint binding_point() const;
+
   /// @returns true if the decorations include a LocationDecoration
   bool HasLocationDecoration() const;
   /// @returns true if the decorations include a BuiltinDecoration

src/ast/variable_test.cc

@@ -107,6 +107,47 @@ TEST_F(VariableTest, WithDecorations) {
   EXPECT_EQ(1u, location->value());
 }
 
+TEST_F(VariableTest, BindingPoint) {
+  auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, nullptr,
+                  DecorationList{
+                      create<BindingDecoration>(2),
+                      create<GroupDecoration>(1),
+                  });
+  EXPECT_TRUE(var->binding_point());
+  ASSERT_NE(var->binding_point().binding, nullptr);
+  ASSERT_NE(var->binding_point().group, nullptr);
+  EXPECT_EQ(var->binding_point().binding->value(), 2u);
+  EXPECT_EQ(var->binding_point().group->value(), 1u);
+}
+
+TEST_F(VariableTest, BindingPointoDecorations) {
+  auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, nullptr,
+                  DecorationList{});
+  EXPECT_FALSE(var->binding_point());
+  EXPECT_EQ(var->binding_point().group, nullptr);
+  EXPECT_EQ(var->binding_point().binding, nullptr);
+}
+
+TEST_F(VariableTest, BindingPointMissingGroupDecoration) {
+  auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, nullptr,
+                  DecorationList{
+                      create<BindingDecoration>(2),
+                  });
+  EXPECT_FALSE(var->binding_point());
+  ASSERT_NE(var->binding_point().binding, nullptr);
+  EXPECT_EQ(var->binding_point().binding->value(), 2u);
+  EXPECT_EQ(var->binding_point().group, nullptr);
+}
+
+TEST_F(VariableTest, BindingPointMissingBindingDecoration) {
+  auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, nullptr,
+                  DecorationList{create<GroupDecoration>(1)});
+  EXPECT_FALSE(var->binding_point());
+  ASSERT_NE(var->binding_point().group, nullptr);
+  EXPECT_EQ(var->binding_point().group->value(), 1u);
+  EXPECT_EQ(var->binding_point().binding, nullptr);
+}
+
 TEST_F(VariableTest, ConstantId) {
   auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, nullptr,
                   DecorationList{