Class: Idl::VariableAssignmentAst

Inherits:
AstNode
  • Object
show all
Includes:
Executable
Defined in:
lib/idlc/ast.rb,
lib/idlc/passes/prune.rb,
lib/idlc/passes/gen_adoc.rb

Overview

represents a scalar variable assignment statement

for example, these will result in a VariableAssignmentAst

# given: Bits<XLEN> zero;
zero = XLEN'b0

Constant Summary

Constants inherited from AstNode

AstNode::Bits1Type, AstNode::Bits32Type, AstNode::Bits64Type, AstNode::BoolType, AstNode::ConstBoolType, AstNode::PossiblyUnknownBits1Type, AstNode::PossiblyUnknownBits32Type, AstNode::PossiblyUnknownBits64Type, AstNode::ReachableFunctionCacheType, AstNode::StringType, AstNode::VoidType

Instance Attribute Summary

Attributes inherited from AstNode

#children, #input, #interval, #parent

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Executable

#executable?

Methods inherited from AstNode

#always_terminates?, #declaration?, #executable?, extract_base_var_name, #find_ancestor, #find_dst_registers, #find_referenced_csrs, #find_src_registers, #freeze_tree, #gen_option_adoc, #input_file, input_from_source_yaml, #inspect, #internal_error, interval_from_source_yaml, #lineno, #lines_around, #pass_find_return_values, #path, #print_ast, #reachable_exceptions, #reachable_functions, #set_input_file, #set_input_file_unless_already_set, #source_line_file_offsets, #source_starting_offset, #source_yaml, #starting_line, #text_value, #truncation_warn, #type_error, #unindent, value_else, #value_else, value_error, #value_error, value_try, #value_try, write_back_nested

Constructor Details

#initialize(input, interval, lhs_ast, rhs_ast) ⇒ VariableAssignmentAst

Returns a new instance of VariableAssignmentAst.



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# File 'lib/idlc/ast.rb', line 2847

def initialize(input, interval, lhs_ast, rhs_ast)
  super(input, interval, [lhs_ast, rhs_ast])
  @vars = {}
end

Class Method Details

.from_h(yaml, source_mapper) ⇒ Object 



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# File 'lib/idlc/ast.rb', line 2911

def self.from_h(yaml, source_mapper)
  raise "Bad YAML" unless yaml.key?("kind") && yaml.fetch("kind") == "var_assignment"

  input = input_from_source_yaml(yaml.fetch("source"), source_mapper)
  interval = interval_from_source_yaml(yaml.fetch("source"))
  VariableAssignmentAst.new(
    input, interval,
    T.cast(AstNode.from_h(yaml.fetch("var"), source_mapper), RvalueAst),
    T.cast(AstNode.from_h(yaml.fetch("value"), source_mapper), RvalueAst)
  )
end

Instance Method Details

#const_eval?(symtab) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idlc/ast.rb', line 2827

def const_eval?(symtab)
  return false if !lhs.const_eval?(symtab)

  if rhs.const_eval?(symtab)
    true
  else
    lhs_var = symtab.get(lhs.name)
    type_error "variable #{lhs.name} was not declared" if lhs_var.nil? || !lhs_var.is_a?(Var)

    lhs_var.const_incompatible!
    false
  end
end

#execute(symtab) ⇒ void

This method returns an undefined value.

“execute” the statement by updating the variables in the symbol table

Parameters:

  • symtab (SymbolTable) —

    The symbol table for the context

Raises:

  • ValueError if some part of the statement cannot be executed at compile time



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# File 'lib/idlc/ast.rb', line 2878

def execute(symtab)
  if lhs.is_a?(CsrWriteAst)
    value_error "CSR writes are never compile-time-known"
  else
    variable = var(symtab)

    internal_error "No variable #{lhs.text_value}" if variable.nil?

    unless variable.type.global?
      value_result = value_try do
        variable.value = rhs.value(symtab)
      end
      value_else(value_result) do
        variable.value = nil
        value_error ""
      end
    end
  end
end

#gen_adoc(indent = 0, indent_spaces: 2) ⇒ Object 



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# File 'lib/idlc/passes/gen_adoc.rb', line 246

def gen_adoc(indent = 0, indent_spaces: 2)
  "#{' ' * indent}#{lhs.gen_adoc(0, indent_spaces:)} = #{rhs.gen_adoc(0, indent_spaces:)}"
end

#lhs ⇒ Object 



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# File 'lib/idlc/ast.rb', line 2842

def lhs = T.cast(@children.fetch(0), IdAst)

#nullify_assignments(symtab) ⇒ Object 



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# File 'lib/idlc/passes/prune.rb', line 137

def nullify_assignments(symtab)
  sym = symtab.get(lhs.text_value)
  unless sym.nil?
    sym.value = nil
  end
end

#prune(symtab, forced_type: nil) ⇒ Object 



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# File 'lib/idlc/passes/prune.rb', line 129

def prune(symtab, forced_type: nil)
  new_ast = VariableAssignmentAst.new(input, interval, lhs.dup, rhs.prune(symtab))
  value_try do
    new_ast.execute(symtab)
  end
  # value_else: execute already sets nil on failure, nothing more to do
  new_ast
end

#rhs ⇒ Object 



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# File 'lib/idlc/ast.rb', line 2845

def rhs = T.cast(@children.fetch(1), RvalueAst)

#to_h ⇒ Object 



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# File 'lib/idlc/ast.rb', line 2903

def to_h = {
  "kind" => "var_assignment",
  "var" => lhs.to_h,
  "value" => rhs.to_h,
  "source" => source_yaml
}

#to_idl ⇒ Object 



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# File 'lib/idlc/ast.rb', line 2900

def to_idl = "#{lhs.to_idl} = #{rhs.to_idl}"

#type_check(symtab, strict:) ⇒ void

This method returns an undefined value.

type check this node and all children

Calls to #type and/or #value may depend on type_check being called first with the same symtab. If not, those functions may raise an AstNode::InternalError

Parameters:

Raises:



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# File 'lib/idlc/ast.rb', line 2853

def type_check(symtab, strict:)
  lhs.type_check(symtab, strict:)
  lhs_var = symtab.get(lhs.name)
  type_error "Cannot assign to a const" if lhs_var.type.const? && !lhs_var.for_loop_iter?

  rhs.type_check(symtab, strict:)
  if lhs_var.type.const? && lhs_var.for_loop_iter?
    # also check that the rhs is const_eval
    type_error "Assignment would make iteration variable non-const" unless rhs.type(symtab).const?
  end
  unless rhs.type(symtab).convertable_to?(lhs.type(symtab))
    type_error "Incompatible type in assignment (#{lhs.type(symtab)}, #{rhs.type(symtab)})"
  end
end

#var(symtab) ⇒ Object 



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# File 'lib/idlc/ast.rb', line 2868

def var(symtab)
  variable = @vars[symtab.name]
  if variable.nil?
    variable = symtab.get(lhs.text_value)
    @vars[symtab.name] = variable
  end
  variable
end