Class: MilkTea::CompileTime::Evaluator

Inherits:
Object
  • Object
show all
Defined in:
lib/milk_tea/core/compile_time.rb

Instance Method Summary collapse

Constructor Details

#initialize(resolve_identifier:, resolve_member_access:, resolve_type_ref: nil, resolve_call: nil) ⇒ Evaluator

Returns a new instance of Evaluator.



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# File 'lib/milk_tea/core/compile_time.rb', line 84

def initialize(resolve_identifier:, resolve_member_access:, resolve_type_ref: nil, resolve_call: nil)
  @resolve_identifier = resolve_identifier
  @resolve_member_access = resolve_member_access
  @resolve_type_ref = resolve_type_ref
  @resolve_call = resolve_call
end

Instance Method Details

#evaluate(expression) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 91

def evaluate(expression)
  case expression
  when AST::ErrorExpr
    nil
  when AST::ExpressionList
    expression.elements.filter_map { |element| evaluate(element) }
  when AST::RangeExpr
    start_val = evaluate(expression.start_expr)
    end_val = evaluate(expression.end_expr)
    start_val.is_a?(Integer) && end_val.is_a?(Integer) ? (start_val...end_val).to_a : nil
  when AST::IntegerLiteral, AST::FloatLiteral, AST::BooleanLiteral, AST::CharLiteral
    expression.value
  when AST::StringLiteral
    expression.value
  when AST::Identifier
    @resolve_identifier&.call(expression)
  when AST::MemberAccess
    @resolve_member_access&.call(expression)
  when AST::Call
    @resolve_call&.call(expression)
  when AST::Specialization
    @resolve_call&.call(expression)
  when AST::SizeofExpr
    type = resolve_layout_type(expression.type)
    type && Layout.size_of(type)
  when AST::AlignofExpr
    type = resolve_layout_type(expression.type)
    type && Layout.alignment_of(type)
  when AST::OffsetofExpr
    type = resolve_layout_type(expression.type)
    if type
      result = Layout.offset_of(type, expression.field)
      return result if result

      id_expr = AST::Identifier.new(name: expression.field)
      value = @resolve_identifier&.call(id_expr)
      if value.is_a?(Types::FieldHandle)
        return Layout.offset_of(type, value.field_name)
      end
    end
    nil
  when AST::UnaryOp
    evaluate_unary(expression)
  when AST::BinaryOp
    evaluate_binary(expression)
  when AST::IfExpr
    condition = evaluate(expression.condition)
    return unless CompileTime.boolean_value?(condition)

    evaluate(condition ? expression.then_expression : expression.else_expression)
  when AST::MatchExpr
    evaluate_match_expression(expression)
  when AST::IndexAccess
    evaluate_index_access(expression)
  when AST::PrefixCast
    evaluate_prefix_cast(expression)
  else
    nil
  end
end

#evaluate_binary(expression) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 269

def evaluate_binary(expression)
  left = evaluate(expression.left)

  case expression.operator
  when "and"
    return unless CompileTime.boolean_value?(left)
    return false if left == false

    right = evaluate(expression.right)
    return right if CompileTime.boolean_value?(right)

    return nil
  when "or"
    return unless CompileTime.boolean_value?(left)
    return true if left == true

    right = evaluate(expression.right)
    return right if CompileTime.boolean_value?(right)

    return nil
  end

  right = evaluate(expression.right)

  case expression.operator
  when ".."
    left.is_a?(Integer) && right.is_a?(Integer) ? (left...right).to_a : nil
  when "=="
    CompileTime.equality_result(left, right)
  when "!="
    result = CompileTime.equality_result(left, right)
    result.nil? ? nil : !result
  when "+"
    if left.is_a?(String) && right.is_a?(String)
      left + right
    elsif left.is_a?(Numeric) && right.is_a?(Numeric)
      left + right
    else
      nil
    end
  when "-"
    left.is_a?(Numeric) && right.is_a?(Numeric) ? left - right : nil
  when "*"
    left.is_a?(Numeric) && right.is_a?(Numeric) ? left * right : nil
  when "/"
    return unless left.is_a?(Numeric) && right.is_a?(Numeric)
    raise Error, "division by zero" if zero_numeric?(right)

    left / right
  when "%"
    return unless left.is_a?(Integer) && right.is_a?(Integer)
    raise Error, "modulo by zero" if right.zero?

    left % right
  when "<<"
    left.is_a?(Integer) && right.is_a?(Integer) ? left << right : nil
  when ">>"
    left.is_a?(Integer) && right.is_a?(Integer) ? left >> right : nil
  when "&"
    left.is_a?(Integer) && right.is_a?(Integer) ? left & right : nil
  when "|"
    left.is_a?(Integer) && right.is_a?(Integer) ? left | right : nil
  when "^"
    left.is_a?(Integer) && right.is_a?(Integer) ? left ^ right : nil
  when "<"
    left.is_a?(Numeric) && right.is_a?(Numeric) ? left < right : nil
  when "<="
    left.is_a?(Numeric) && right.is_a?(Numeric) ? left <= right : nil
  when ">"
    left.is_a?(Numeric) && right.is_a?(Numeric) ? left > right : nil
  when ">="
    left.is_a?(Numeric) && right.is_a?(Numeric) ? left >= right : nil
  end
end

#evaluate_index_access(expression) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 197

def evaluate_index_access(expression)
  receiver = evaluate(expression.receiver)
  return nil if receiver.nil?

  if expression.index.is_a?(AST::RangeExpr)
    start_val = evaluate(expression.index.start_expr)
    end_val = evaluate(expression.index.end_expr)
    return nil unless start_val.is_a?(Integer) && end_val.is_a?(Integer)

    return receiver[start_val...end_val] if receiver.is_a?(Array) || receiver.is_a?(String)

    return nil
  end

  index = evaluate(expression.index)
  return nil unless index.is_a?(Integer)
  return receiver[index] if receiver.is_a?(Array)
  return receiver.getbyte(index) if receiver.is_a?(String)

  nil
end

#evaluate_match_expression(expression) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 219

def evaluate_match_expression(expression)
  scrutinee = evaluate(expression.expression)
  return nil unless scrutinee

  expression.arms.each do |arm|
    wildcard = arm.pattern.is_a?(AST::Identifier) && arm.pattern.name == "_"
    if wildcard || CompileTime.equality_result(scrutinee, evaluate(arm.pattern)) == true
      return evaluate(arm.value)
    end
  end

  nil
end

#evaluate_prefix_cast(expression) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 152

def evaluate_prefix_cast(expression)
  operand = evaluate(expression.expression)
  operand = 1 if operand == true
  operand = 0 if operand == false
  return nil unless operand.is_a?(Numeric)

  target_type = begin
    @resolve_type_ref&.call(expression.target_type)
  rescue SemanticError
    nil
  end
  return nil unless target_type.is_a?(Types::Primitive)

  if target_type.boolean?
    return operand != 0
  end

  if target_type.integer?
    return nil unless target_type.integer_width

    value = operand.is_a?(Float) ? operand.truncate : operand
    return nil unless value.is_a?(Integer)

    return wrap_integer(value, target_type.integer_width, target_type.signed_integer?)
  end

  return nil unless target_type.float?

  value = operand.to_f
  target_type.name == "float" ? float32_round(value) : value
end

#evaluate_unary(expression) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 254

def evaluate_unary(expression)
  operand = evaluate(expression.operand)

  case expression.operator
  when "+"
    operand.is_a?(Numeric) ? operand : nil
  when "-"
    operand.is_a?(Numeric) ? -operand : nil
  when "~"
    operand.is_a?(Integer) ? ~operand : nil
  when "not"
    CompileTime.boolean_value?(operand) ? !operand : nil
  end
end

#float32_round(value) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 193

def float32_round(value)
  [value].pack("f").unpack1("f")
end

#resolve_layout_type(type_ref) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 233

def resolve_layout_type(type_ref)
  result = begin
    @resolve_type_ref&.call(type_ref)
  rescue SemanticError
    nil
  end
  return result if result

  return unless type_ref.respond_to?(:name) && type_ref.name.parts.length >= 1

  expression = ::MilkTea::AST.build_chain_from_parts(type_ref.name.parts)
  return unless expression

  value = evaluate(expression)
  return value if value.is_a?(Types::Struct) || value.is_a?(Types::Primitive) ||
    value.is_a?(Types::Union) || value.is_a?(Types::Nullable) ||
    value.is_a?(Types::StructInstance)

  nil
end

#wrap_integer(value, width, signed) ⇒ Object 



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# File 'lib/milk_tea/core/compile_time.rb', line 184

def wrap_integer(value, width, signed)
  mask = (1 << width) - 1
  wrapped = value & mask
  return wrapped unless signed

  half = 1 << (width - 1)
  wrapped >= half ? wrapped - (1 << width) : wrapped
end

#zero_numeric?(value) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/milk_tea/core/compile_time.rb', line 344

def zero_numeric?(value)
  (value.is_a?(Integer) && value.zero?) || (value.is_a?(Float) && value.zero?)
end