Class: SyntaxTree::YARV::BasicBlock

Inherits:
Object
  • Object
show all
Defined in:
lib/syntax_tree/yarv/basic_block.rb

Overview

This object represents a single basic block, wherein all contained instructions do not branch except for the last one.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(block_start, insns) ⇒ BasicBlock

Returns a new instance of BasicBlock.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 23

def initialize(block_start, insns)
  @id = "block_#{block_start}"

  @block_start = block_start
  @insns = insns

  @incoming_blocks = []
  @outgoing_blocks = []
end

Instance Attribute Details

#block_start ⇒ Object (readonly)

This is the index into the list of instructions where this block starts.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 12

def block_start
  @block_start
end

#id ⇒ Object (readonly)

This is the unique identifier for this basic block.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 9

def id
  @id
end

#incoming_blocks ⇒ Object (readonly)

This is an array of basic blocks that lead into this block.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 18

def incoming_blocks
  @incoming_blocks
end

#insns ⇒ Object (readonly)

This is the set of instructions that this block contains.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 15

def insns
  @insns
end

#outgoing_blocks ⇒ Object (readonly)

This is an array of basic blocks that this block leads into.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 21

def outgoing_blocks
  @outgoing_blocks
end

Instance Method Details

#each_with_length ⇒ Object

Yield each instruction in this basic block along with its index from the original instruction sequence.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 35

def each_with_length
  return enum_for(:each_with_length) unless block_given?

  length = block_start
  insns.each do |insn|
    yield insn, length
    length += insn.length
  end
end

#verify ⇒ Object

This method is used to verify that the basic block is well formed. It checks that the only instruction in this basic block that branches is the last instruction.



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# File 'lib/syntax_tree/yarv/basic_block.rb', line 48

def verify
  insns[0...-1].each { |insn| raise unless insn.branch_targets.empty? }
end