sem: Add FunctionBlockStatement

BlockStatement for the root block of a function

Add some basic tests for this lot.

Bug: tint:812
Change-Id: I26b65717798cbff576a44bd78fbcb5c8f0d013e6
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51368
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Alastair Donaldson <allydonaldson@googlemail.com>

src/sem/block_statement.cc

@@ -15,8 +15,11 @@
 #include "src/sem/block_statement.h"
 
 #include "src/ast/block_statement.h"
+#include "src/ast/function.h"
+#include "src/sem/function.h"
 
 TINT_INSTANTIATE_TYPEINFO(tint::sem::BlockStatement);
+TINT_INSTANTIATE_TYPEINFO(tint::sem::FunctionBlockStatement);
 TINT_INSTANTIATE_TYPEINFO(tint::sem::LoopBlockStatement);
 TINT_INSTANTIATE_TYPEINFO(tint::sem::LoopContinuingBlockStatement);
 TINT_INSTANTIATE_TYPEINFO(tint::sem::SwitchCaseBlockStatement);
@@ -38,6 +41,11 @@ void BlockStatement::AddDecl(ast::Variable* var) {
   decls_.push_back(var);
 }
 
+FunctionBlockStatement::FunctionBlockStatement(const ast::Function* function)
+    : Base(function->body(), nullptr), function_(function) {}
+
+FunctionBlockStatement::~FunctionBlockStatement() = default;
+
 LoopBlockStatement::LoopBlockStatement(const ast::BlockStatement* declaration,
                                        const Statement* parent)
     : Base(declaration, parent) {}

src/sem/block_statement.h

@@ -19,14 +19,16 @@
 
 #include "src/sem/statement.h"
 
-namespace tint {
-
 // Forward declarations
+namespace tint {
 namespace ast {
 class BlockStatement;
+class Function;
 class Variable;
 }  // namespace ast
+}  // namespace tint
 
+namespace tint {
 namespace sem {
 
 /// Holds semantic information about a block, such as parent block and variables
@@ -84,6 +86,24 @@ class BlockStatement : public Castable<BlockStatement, Statement> {
   std::vector<const ast::Variable*> decls_;
 };
 
+/// The root block statement for a function
+class FunctionBlockStatement
+    : public Castable<FunctionBlockStatement, BlockStatement> {
+ public:
+  /// Constructor
+  /// @param function the owning function
+  explicit FunctionBlockStatement(const ast::Function* function);
+
+  /// Destructor
+  ~FunctionBlockStatement() override;
+
+  /// @returns the function owning this block
+  const ast::Function* Function() const { return function_; }
+
+ private:
+  ast::Function const* const function_;
+};
+
 /// Holds semantic information about a loop block
 class LoopBlockStatement : public Castable<LoopBlockStatement, BlockStatement> {
  public:

src/sem/statement.cc

@@ -65,5 +65,14 @@ const BlockStatement* Statement::Block() const {
   return nullptr;
 }
 
+const ast::Function* Statement::Function() const {
+  if (auto* block = Block()) {
+    if (auto* fbs = block->FindFirstParent<FunctionBlockStatement>()) {
+      return fbs->Function();
+    }
+  }
+  return nullptr;
+}
+
 }  // namespace sem
 }  // namespace tint

src/sem/statement.h

@@ -17,16 +17,19 @@
 
 #include "src/sem/node.h"
 
-namespace tint {
-
 // Forward declarations
+namespace tint {
 namespace ast {
+class Function;
 class Statement;
 }  // namespace ast
-
 namespace sem {
-
 class BlockStatement;
+}  // namespace sem
+}  // namespace tint
+
+namespace tint {
+namespace sem {
 
 /// Statement holds the semantic information for a statement.
 class Statement : public Castable<Statement, Node> {
@@ -45,6 +48,9 @@ class Statement : public Castable<Statement, Node> {
   /// @return the closest enclosing block for this statement
   const BlockStatement* Block() const;
 
+  /// @returns the function that owns this statement
+  const ast::Function* Function() const;
+
  private:
   ast::Statement const* const declaration_;
   Statement const* const parent_;