[ast] Add helpers for searching a decoration list

This is a commonly used pattern.

Change-Id: I698397c93c33db64c53cbe8662186e1976075b80
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/47280
Auto-Submit: James Price <jrprice@google.com>
Commit-Queue: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/ast/decoration.h

@@ -36,6 +36,30 @@ class Decoration : public Castable<Decoration, Node> {
 /// A list of decorations
 using DecorationList = std::vector<Decoration*>;
 
+/// @param decorations the list of decorations to search
+/// @returns true if `decorations` includes a decoration of type `T`
+template <typename T>
+bool HasDecoration(const DecorationList& decorations) {
+  for (auto* deco : decorations) {
+    if (deco->Is<T>()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/// @param decorations the list of decorations to search
+/// @returns a pointer to `T` from `decorations` if found, otherwise nullptr.
+template <typename T>
+T* GetDecoration(const DecorationList& decorations) {
+  for (auto* deco : decorations) {
+    if (deco->Is<T>()) {
+      return deco->As<T>();
+    }
+  }
+  return nullptr;
+}
+
 }  // namespace ast
 }  // namespace tint
 

src/ast/function.cc

@@ -49,19 +49,15 @@ Function::Function(Function&&) = default;
 Function::~Function() = default;
 
 std::tuple<uint32_t, uint32_t, uint32_t> Function::workgroup_size() const {
-  for (auto* deco : decorations_) {
-    if (auto* workgroup = deco->As<WorkgroupDecoration>()) {
-      return workgroup->values();
-    }
+  if (auto* workgroup = GetDecoration<WorkgroupDecoration>(decorations_)) {
+    return workgroup->values();
   }
   return {1, 1, 1};
 }
 
 PipelineStage Function::pipeline_stage() const {
-  for (auto* deco : decorations_) {
-    if (auto* stage = deco->As<StageDecoration>()) {
-      return stage->value();
-    }
+  if (auto* stage = GetDecoration<StageDecoration>(decorations_)) {
+    return stage->value();
   }
   return PipelineStage::kNone;
 }

src/ast/function.h

@@ -63,18 +63,6 @@ class Function : public Castable<Function, Node> {
   /// @returns the decorations attached to this function
   const DecorationList& decorations() const { return decorations_; }
 
-  /// @returns the decoration with the type `T` or nullptr if this function does
-  /// not contain a decoration with the given type
-  template <typename T>
-  const T* find_decoration() const {
-    for (auto* deco : decorations()) {
-      if (auto* d = deco->As<T>()) {
-        return d;
-      }
-    }
-    return nullptr;
-  }
-
   /// @returns the workgroup size {x, y, z} for the function. {1, 1, 1} will be
   /// return if no workgroup size was set.
   std::tuple<uint32_t, uint32_t, uint32_t> workgroup_size() const;

src/ast/struct.cc

@@ -50,12 +50,7 @@ StructMember* Struct::get_member(const Symbol& symbol) const {
 }
 
 bool Struct::IsBlockDecorated() const {
-  for (auto* deco : decorations_) {
-    if (deco->Is<StructBlockDecoration>()) {
-      return true;
-    }
-  }
-  return false;
+  return HasDecoration<StructBlockDecoration>(decorations_);
 }
 
 Struct* Struct::Clone(CloneContext* ctx) const {

src/ast/struct_member.cc

@@ -41,19 +41,13 @@ StructMember::StructMember(StructMember&&) = default;
 StructMember::~StructMember() = default;
 
 bool StructMember::has_offset_decoration() const {
-  for (auto* deco : decorations_) {
-    if (deco->Is<StructMemberOffsetDecoration>()) {
-      return true;
-    }
-  }
-  return false;
+  return HasDecoration<StructMemberOffsetDecoration>(decorations_);
 }
 
 uint32_t StructMember::offset() const {
-  for (auto* deco : decorations_) {
-    if (auto* offset = deco->As<StructMemberOffsetDecoration>()) {
-      return offset->offset();
-    }
+  if (auto* offset =
+          GetDecoration<StructMemberOffsetDecoration>(decorations_)) {
+    return offset->offset();
   }
   return 0;
 }

src/ast/variable.cc

@@ -59,49 +59,11 @@ Variable::BindingPoint Variable::binding_point() const {
   return BindingPoint{group, binding};
 }
 
-bool Variable::HasLocationDecoration() const {
-  for (auto* deco : decorations_) {
-    if (deco->Is<LocationDecoration>()) {
-      return true;
-    }
-  }
-  return false;
-}
-
-bool Variable::HasBuiltinDecoration() const {
-  for (auto* deco : decorations_) {
-    if (deco->Is<BuiltinDecoration>()) {
-      return true;
-    }
-  }
-  return false;
-}
-
-bool Variable::HasConstantIdDecoration() const {
-  for (auto* deco : decorations_) {
-    if (deco->Is<ConstantIdDecoration>()) {
-      return true;
-    }
-  }
-  return false;
-}
-
-LocationDecoration* Variable::GetLocationDecoration() const {
-  for (auto* deco : decorations_) {
-    if (deco->Is<LocationDecoration>()) {
-      return deco->As<LocationDecoration>();
-    }
-  }
-  return nullptr;
-}
-
 uint32_t Variable::constant_id() const {
-  TINT_ASSERT(HasConstantIdDecoration());
-  for (auto* deco : decorations_) {
-    if (auto* cid = deco->As<ConstantIdDecoration>()) {
-      return cid->value();
-    }
+  if (auto* cid = GetDecoration<ConstantIdDecoration>(decorations_)) {
+    return cid->value();
   }
+  TINT_ASSERT(false);
   return 0;
 }
 

src/ast/variable.h

@@ -134,18 +134,8 @@ class Variable : public Castable<Variable, Node> {
   /// @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
-  bool HasBuiltinDecoration() const;
-  /// @returns true if the decorations include a ConstantIdDecoration
-  bool HasConstantIdDecoration() const;
-
-  /// @returns pointer to LocationDecoration in decorations, otherwise NULL.
-  LocationDecoration* GetLocationDecoration() const;
-
-  /// @returns the constant_id value for the variable. Assumes that
-  /// HasConstantIdDecoration() has been called first.
+  /// @returns the constant_id value for the variable. Assumes that this
+  /// variable has a constant ID decoration.
   uint32_t constant_id() const;
 
   /// Clones this node and all transitive child nodes using the `CloneContext`

src/ast/variable_test.cc

@@ -98,11 +98,12 @@ TEST_F(VariableTest, WithDecorations) {
                       create<ConstantIdDecoration>(1200),
                   });
 
-  EXPECT_TRUE(var->HasLocationDecoration());
-  EXPECT_TRUE(var->HasBuiltinDecoration());
-  EXPECT_TRUE(var->HasConstantIdDecoration());
+  auto& decorations = var->decorations();
+  EXPECT_TRUE(ast::HasDecoration<ast::LocationDecoration>(decorations));
+  EXPECT_TRUE(ast::HasDecoration<ast::BuiltinDecoration>(decorations));
+  EXPECT_TRUE(ast::HasDecoration<ast::ConstantIdDecoration>(decorations));
 
-  auto* location = var->GetLocationDecoration();
+  auto* location = ast::GetDecoration<ast::LocationDecoration>(decorations);
   ASSERT_NE(nullptr, location);
   EXPECT_EQ(1u, location->value());
 }