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a bit of cleanup and the good news is, we can output a (small) number

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Torsten Ruger
2014-05-16 23:24:19 +03:00
parent fee82643e5
commit a08661955f
2 changed files with 12 additions and 28 deletions
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18
lib/arm/arm_machine.rb
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@ -74,31 +74,21 @@ module Arm
# the number (a Vm::integer) is (itself) divided by 10, ie overwritten by the result
# and the remainder is overwritten (ie an out argument)
# not really a function, more a macro, hence private
# not really a function, more a macro,
def div10 block, number , remainder
# takes argument in r1
# returns quotient in r1, remainder in r2
# SUB r2, r1, #10 # keep (x-10) for later
# Note about division: devision is MUCH more expensive than one would have thought
# And coding it is a bit of a mind leap: it's all about finding a a result that gets the
# remainder smaller than an int. i'll post some links sometime. This is from the arm manual
block.add_code sub( remainder , left: number , right: 10 )
# SUB r1, r1, r1, lsr #2
block.add_code sub( number , left: number , right: number , shift_lsr: 2)
# ADD r1, r1, r1, lsr #4
block.add_code add( number , left: number , right: number , shift_lsr: 4)
# ADD r1, r1, r1, lsr #8
block.add_code add( number , left: number , right: number , shift_lsr: 8)
# ADD r1, r1, r1, lsr #16
block.add_code add( number , left: number , right: number , shift_lsr: 16)
# MOV r1, r1, lsr #3
block.add_code mov( number , right: number , shift_lsr: 3)
# ADD r3, r1, r1, asl #2
tmp = Vm::Integer.new( remainder.register + 1)
block.add_code add( tmp , left: number , right: number , shift_lsl: 2)
# SUBS r2, r2, r3, asl #1 # calc (x-10) - (x/10)*10
block.add_code sub( remainder , left: remainder , right: tmp , shift_lsl: 1 , update_status: 1)
# ADDPL r1, r1, #1 # fix-up quotient
block.add_code add( number , left: number, right: 1 , condition_code: :pl )
# ADDMI r2, r2, #10 # fix-up remainder
block.add_code add( remainder , left: remainder , right: 10 , condition_code: :mi )
end