Module: Optimize::Passes::LiteralValue

Defined in:
lib/optimize/passes/literal_value.rb

Overview

Reads and emits literal-producer instructions.

Ruby 4.0.2 literal-producer shapes we recognize (confirmed via RubyVM::InstructionSequence disassembly on Ruby 4.0.2):

putobject_INT2FIX_0_     — pushes 0 (no operand)
putobject_INT2FIX_1_     — pushes 1 (no operand)
putobject <index>        — pushes object_table.objects[index]
putchilledstring <index> — default string literal in 4.0.2; pushes the
                           String at object_table.objects[index]
putstring <index>        — mutable-string variant; same operand shape
putnil                   — pushes nil (no operand)

‘read` returning nil is ambiguous (putnil legitimately reads as nil, and an unrecognized opcode also returns nil). Callers that need to distinguish “literal nil” from “not a literal” must use `literal?`.

‘emit` is unchanged from the Integer/boolean tier — it only knows how to emit putobject-family opcodes.

Constant Summary collapse

LITERAL_OPCODES = 
%i[
  putobject
  putobject_INT2FIX_0_
  putobject_INT2FIX_1_
  putchilledstring
  putstring
  putnil
].freeze

Class Method Summary collapse

Class Method Details

.emit(value, line:, object_table:) ⇒ IR::Instruction

Parameters:

Returns:



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# File 'lib/optimize/passes/literal_value.rb', line 62

def emit(value, line:, object_table:)
  case value
  when 0
    IR::Instruction.new(opcode: :putobject_INT2FIX_0_, operands: [], line: line)
  when 1
    IR::Instruction.new(opcode: :putobject_INT2FIX_1_, operands: [], line: line)
  else
    idx = object_table.intern(value)
    IR::Instruction.new(opcode: :putobject, operands: [idx], line: line)
  end
end

.literal?(inst) ⇒ Boolean

Returns true iff ‘inst` is a recognized literal producer.

Parameters:

Returns:

  • (Boolean) —

    true iff ‘inst` is a recognized literal producer.



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# File 'lib/optimize/passes/literal_value.rb', line 38

def literal?(inst)
  LITERAL_OPCODES.include?(inst.opcode)
end

.read(inst, object_table:) ⇒ Object?

Returns the pushed value. Returns nil for :putnil AND for unrecognized opcodes — use ‘literal?` to disambiguate.

Parameters:

Returns:

  • (Object, nil) —

    the pushed value. Returns nil for :putnil AND for unrecognized opcodes — use ‘literal?` to disambiguate.



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# File 'lib/optimize/passes/literal_value.rb', line 46

def read(inst, object_table:)
  case inst.opcode
  when :putobject_INT2FIX_0_ then 0
  when :putobject_INT2FIX_1_ then 1
  when :putnil               then nil
  when :putobject, :putchilledstring, :putstring
    idx = inst.operands[0]
    return nil unless idx.is_a?(Integer)
    object_table.objects[idx]
  end
end