[LLDB] Add type casting to DIL.

This adds basic c-style type casting to DIL. It handles basic
built-in types: bool, char, short, int, long, double, float, and void.
It also handles user-defined types (e.g. class names, typedefs, etc.).
It does NOT handle C++ templates at the moment. Not sure if this is
something we would want to add to DIL later or not. DIL will not
be supporting C++-specific-style casts (static_cast<>, reinterpret_cast<>,
or dynamic_cast<>).

This PR adds quite a bit of type-parsing, which must happen in the
parser, to resolve ambiguity ("is this thing I'm looking at a type cast
or just an expression in parentheses?").

I'd be happy to break this up into smaller PRs if someone could suggest
a reasonable way to break it up.

Author: cmtice

lldb/docs/dil-expr-lang.ebnf

@@ -3,10 +3,13 @@
 (* This is currently a subset of the final DIL Language, matching the current
    DIL implementation. *)
 
-expression = unary_expression ;
+expression = cast_expression;
+
+cast_expression = unary_expression
+                | "(" type_id ")" cast_expression;
 
 unary_expression = postfix_expression
-                 | unary_operator expression ;
+                 | unary_operator cast_expression ;
 
 unary_operator = "*" | "&" ;
 
@@ -41,6 +44,31 @@ nested_name_specifier = type_name "::"
                       | namespace_name '::'
                       | nested_name_specifier identifier "::" ;
 
+type_id = type_specifier_seq [abstract_declarator] ;
+
+type_specifier_seq = type_specifier [type_specifier];
+
+type_specifier = ["::"] [nested_name_specifier] type_name;
+               | "char"
+               | "bool"
+               | "short"
+               | "int"
+               | "long"
+               | "signed"
+               | "unsigned"
+               | "float"
+               | "double"
+               | "void" ;
+
+nested_name_specifier = type_name "::"
+                      | namespace_name "::"
+                      | nested_name_specifier identifier "::" ;
+
+abstract_declarator = ptr_operator [abstract_declarator] ;
+
+ptr_operator = "*"
+             | "&";
+
 type_name = class_name
           | enum_name
           | typedef_name;

lldb/include/lldb/ValueObject/DILAST.h

@@ -20,6 +20,7 @@ namespace lldb_private::dil {
 enum class NodeKind {
   eArraySubscriptNode,
   eBitExtractionNode,
+  eCStyleCastNode,
   eErrorNode,
   eFloatLiteralNode,
   eIdentifierNode,
@@ -28,6 +29,21 @@ enum class NodeKind {
   eUnaryOpNode,
 };
 
+/// The C-Style casts allowed by DIL.
+enum class CStyleCastKind {
+  eEnumeration,
+  eNullptr,
+  eReference,
+  eNone,
+};
+
+/// Promotions for C-Style casts in DIL.
+enum class CastPromoKind {
+  eArithmetic,
+  ePointer,
+  eNone,
+};
+
 /// The Unary operators recognized by DIL.
 enum class UnaryOpKind {
   AddrOf, // "&"
@@ -226,6 +242,29 @@ class FloatLiteralNode : public ASTNode {
   llvm::APFloat m_value;
 };
 
+class CStyleCastNode : public ASTNode {
+public:
+  CStyleCastNode(uint32_t location, CompilerType type, ASTNodeUP operand,
+                 CStyleCastKind kind)
+      : ASTNode(location, NodeKind::eCStyleCastNode), m_type(type),
+        m_operand(std::move(operand)), m_cast_kind(kind) {}
+
+  llvm::Expected<lldb::ValueObjectSP> Accept(Visitor *v) const override;
+
+  CompilerType GetType() const { return m_type; }
+  ASTNode *GetOperand() const { return m_operand.get(); }
+  CStyleCastKind GetCastKind() const { return m_cast_kind; }
+
+  static bool classof(const ASTNode *node) {
+    return node->GetKind() == NodeKind::eCStyleCastNode;
+  }
+
+private:
+  CompilerType m_type;
+  ASTNodeUP m_operand;
+  CStyleCastKind m_cast_kind;
+};
+
 /// This class contains one Visit method for each specialized type of
 /// DIL AST node. The Visit methods are used to dispatch a DIL AST node to
 /// the correct function in the DIL expression evaluator for evaluating that
@@ -247,6 +286,8 @@ class Visitor {
   Visit(const IntegerLiteralNode *node) = 0;
   virtual llvm::Expected<lldb::ValueObjectSP>
   Visit(const FloatLiteralNode *node) = 0;
+  virtual llvm::Expected<lldb::ValueObjectSP>
+  Visit(const CStyleCastNode *node) = 0;
 };
 
 } // namespace lldb_private::dil

lldb/include/lldb/ValueObject/DILEval.h

@@ -58,12 +58,19 @@ class Interpreter : Visitor {
   Visit(const IntegerLiteralNode *node) override;
   llvm::Expected<lldb::ValueObjectSP>
   Visit(const FloatLiteralNode *node) override;
+  llvm::Expected<lldb::ValueObjectSP>
+  Visit(const CStyleCastNode *node) override;
 
   llvm::Expected<CompilerType>
   PickIntegerType(lldb::TypeSystemSP type_system,
                   std::shared_ptr<ExecutionContextScope> ctx,
                   const IntegerLiteralNode *literal);
 
+  llvm::Expected<CompilerType>
+  VerifyCStyleCastType(lldb::ValueObjectSP &operand, CompilerType &op_type,
+                       CompilerType target_type, CastPromoKind &promo_kind,
+                       CStyleCastKind &cast_kind, int location);
+
   // Used by the interpreter to create objects, perform casts, etc.
   lldb::TargetSP m_target;
   llvm::StringRef m_expr;

lldb/include/lldb/ValueObject/DILParser.h

@@ -10,6 +10,7 @@
 #define LLDB_VALUEOBJECT_DILPARSER_H
 
 #include "lldb/Target/ExecutionContextScope.h"
+#include "lldb/Target/StackFrame.h"
 #include "lldb/Utility/DiagnosticsRendering.h"
 #include "lldb/Utility/Status.h"
 #include "lldb/ValueObject/DILAST.h"
@@ -31,6 +32,9 @@ enum class ErrorCode : unsigned char {
   kUnknown,
 };
 
+llvm::Expected<lldb::TypeSystemSP>
+DILGetTypeSystemFromCU(std::shared_ptr<StackFrame> ctx);
+
 // The following is modeled on class OptionParseError.
 class DILDiagnosticError
     : public llvm::ErrorInfo<DILDiagnosticError, DiagnosticError> {
@@ -55,6 +59,61 @@ class DILDiagnosticError
 
   std::string message() const override { return m_detail.rendered; }
 };
+/// TypeDeclaration builds information about the literal type definition as
+/// type is being parsed. It doesn't perform semantic analysis for non-basic
+/// types -- e.g. "char&&&" is a valid type declaration.
+/// NOTE: CV qualifiers are ignored.
+class TypeDeclaration {
+public:
+  enum class TypeSpecifier {
+    kBool,
+    kChar,
+    kDouble,
+    kFloat,
+    kInt,
+    kLong,
+    kLongDouble,
+    kLongLong,
+    kShort,
+    kUnknown,
+    kVoid,
+  };
+
+  enum class SignSpecifier {
+    kUnknown,
+    kSigned,
+    kUnsigned,
+  };
+
+  bool IsEmpty() const { return !m_is_builtin && !m_is_user_type; }
+
+  lldb::BasicType GetBasicType() const;
+
+public:
+  // Indicates user-defined typename (e.g. "MyClass", "MyTmpl<int>").
+  std::string m_user_typename;
+
+  // Basic type specifier ("void", "char", "intr", "float", "long long", etc.).
+  TypeSpecifier m_type_specifier = TypeSpecifier::kUnknown;
+
+  // Signedness specifier ("signed", "unsigned").
+  SignSpecifier m_sign_specifier = SignSpecifier::kUnknown;
+
+  // Does the type declaration includes "int" specifier?
+  // This is different than `type_specifier_` and is used to detect "int"
+  // duplication for types that can be combined with "int" specifier (e.g.
+  // "short int", "long int").
+  bool m_has_int_specifier = false;
+
+  // Indicates whether there was an error during parsing.
+  bool m_has_error = false;
+
+  // Indicates whether this declaration describes a builtin type.
+  bool m_is_builtin = false;
+
+  // Indicates whether this declaration describes a user type.
+  bool m_is_user_type = false;
+}; // class TypeDeclaration
 
 /// Pure recursive descent parser for C++ like expressions.
 /// EBNF grammar for the parser is described in lldb/docs/dil-expr-lang.ebnf
@@ -100,10 +159,22 @@ class DILParser {
   ASTNodeUP ParseIntegerLiteral();
   ASTNodeUP ParseFloatingPointLiteral();
 
+  ASTNodeUP ParseCastExpression();
+  std::optional<CompilerType> ParseTypeId(bool must_be_type_id = false);
+  void ParseTypeSpecifierSeq(TypeDeclaration *type_decl);
+  bool ParseTypeSpecifier(TypeDeclaration *type_decl);
+  std::string ParseTypeName();
+  CompilerType ResolveTypeDeclarators(CompilerType type,
+                                      const std::vector<Token> &ptr_operators);
+  bool IsSimpleTypeSpecifierKeyword(Token token) const;
+  bool HandleSimpleTypeSpecifier(TypeDeclaration *type_decl);
+
   void BailOut(const std::string &error, uint32_t loc, uint16_t err_len);
 
   void Expect(Token::Kind kind);
 
+  void ExpectOneOf(std::vector<Token::Kind> kinds_vec);
+
   void TentativeParsingRollback(uint32_t saved_idx) {
     if (m_error)
       llvm::consumeError(std::move(m_error));
@@ -132,4 +203,66 @@ class DILParser {
 
 } // namespace lldb_private::dil
 
+namespace llvm {
+template <>
+struct format_provider<lldb_private::dil::TypeDeclaration::TypeSpecifier> {
+  static void format(const lldb_private::dil::TypeDeclaration::TypeSpecifier &t,
+                     raw_ostream &OS, llvm::StringRef Options) {
+    switch (t) {
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kVoid:
+      OS << "void";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kBool:
+      OS << "bool";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kChar:
+      OS << "char";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kInt:
+      OS << "int";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kFloat:
+      OS << "float";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kShort:
+      OS << "short";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kLong:
+      OS << "long";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kLongLong:
+      OS << "long long";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kDouble:
+      OS << "double";
+      break;
+    case lldb_private::dil::TypeDeclaration::TypeSpecifier::kLongDouble:
+      OS << "long double";
+      break;
+    default:
+      OS << "invalid type specifier";
+      break;
+    }
+  }
+};
+
+template <>
+struct format_provider<lldb_private::dil::TypeDeclaration::SignSpecifier> {
+  static void format(const lldb_private::dil::TypeDeclaration::SignSpecifier &t,
+                     raw_ostream &OS, llvm::StringRef Options) {
+    switch (t) {
+    case lldb_private::dil::TypeDeclaration::SignSpecifier::kSigned:
+      OS << "signed";
+      break;
+    case lldb_private::dil::TypeDeclaration::SignSpecifier::kUnsigned:
+      OS << "unsigned";
+      break;
+    default:
+      OS << "invalid sign specifier";
+      break;
+    }
+  }
+};
+} // namespace llvm
+
 #endif // LLDB_VALUEOBJECT_DILPARSER_H

lldb/source/ValueObject/DILAST.cpp

@@ -46,4 +46,8 @@ llvm::Expected<lldb::ValueObjectSP> FloatLiteralNode::Accept(Visitor *v) const {
   return v->Visit(this);
 }
 
+llvm::Expected<lldb::ValueObjectSP> CStyleCastNode::Accept(Visitor *v) const {
+  return v->Visit(this);
+}
+
 } // namespace lldb_private::dil