rubyx/lib/arm/stack_instruction.rb
2014-05-14 10:47:30 +03:00

71 lines
2.1 KiB
Ruby

require "vm/instruction"
require_relative "constants"
module Arm
# ADDRESSING MODE 4
class StackInstruction < Vm::StackInstruction
include Arm::Constants
# arm intrucioons are pretty sensible, and always 4 bytes (thumb not supported)
def length
4
end
def initialize(attributes)
super(attributes)
@attributes[:update_status_flag] = 0 if @attributes[:update_status_flag] == nil
@attributes[:condition_code] = :al if @attributes[:condition_code] == nil
@attributes[:opcode] = attributes[:opcode]
@operand = 0
@attributes[:update_status_flag]= 0
@rn = :r0 # register zero = zero bit pattern
# downward growing, decrement before memory access
# official ARM style stack as used by gas
end
def assemble(io)
build
write_base = 1
if (opcode == :push)
pre_post_index = 1
up_down = 0
is_pop = 0
else #pop
pre_post_index = 0
up_down = 1
is_pop = 1
end
instuction_class = 0b10 # OPC_STACK
cond = @attributes[:condition_code].is_a?(Symbol) ? COND_CODES[@attributes[:condition_code]] : @attributes[:condition_code]
@rn = :sp # sp register
#assemble of old
val = @operand
val |= (reg_code(@rn) << 16)
val |= (is_pop << 16+4) #20
val |= (write_base << 16+4+ 1)
val |= (@attributes[:update_status_flag] << 16+4+ 1+1)
val |= (up_down << 16+4+ 1+1+1)
val |= (pre_post_index << 16+4+ 1+1+1+1)#24
val |= (instuction_class << 16+4+ 1+1+1+1 +2)
val |= (cond << 16+4+ 1+1+1+1 +2+2)
io.write_uint32 val
end
private
# Build representation for source value
def build
regs = @attributes[:regs]
if (regs.is_a?(Array))
@operand = 0
regs.each do |reg |
next unless reg
@operand |= (1 << reg_code(reg))
end
else
raise "invalid operand argument #{regs.inspect} #{inspect}"
end
end
end
end