82 lines
2.9 KiB
Ruby
82 lines
2.9 KiB
Ruby
module Arm
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class MachineCode
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def function_call into , call
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raise "Not CallSite #{call.inspect}" unless call.is_a? Virtual::CallSite
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raise "Not linked #{call.inspect}" unless call.function
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into.add_code call( call.function )
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raise "No return type for #{call.function.name}" unless call.function.return_type
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call.function.return_type
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end
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def main_start context
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entry = Virtual::Block.new("main_entry",nil,nil)
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entry.add_code mov( :fp , 0 )
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entry.add_code call( context.function )
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entry
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end
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def main_exit context
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exit = Virtual::Block.new("main_exit",nil,nil)
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syscall(exit , 1)
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exit
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end
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def function_entry block, f_name
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block.add_code push( [:lr] )
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block
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end
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def function_exit entry , f_name
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entry.add_code pop( [:pc] )
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entry
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end
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# assumes string in standard receiver reg (r2) and moves them down for the syscall
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def write_stdout function #, string
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# TODO save and restore r0
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function.mov( :r0 , 1 ) # 1 == stdout
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function.mov( :r1 , receiver_register )
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function.mov( receiver_register , :r3 )
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syscall( function.insertion_point , 4 ) # 4 == write
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end
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# stop, do not return
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def exit function #, string
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syscall( function.insertion_point , 1 ) # 1 == exit
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end
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# the number (a Virtual::integer) is (itself) divided by 10, ie overwritten by the result
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# and the remainder is overwritten (ie an out argument)
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# not really a function, more a macro,
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def div10 function, number , remainder
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# Note about division: devision is MUCH more expensive than one would have thought
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# And coding it is a bit of a mind leap: it's all about finding a a result that gets the
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# remainder smaller than an int. i'll post some links sometime. This is from the arm manual
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tmp = function.new_local
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function.instance_eval do
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sub( remainder , number , 10 )
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sub( number , number , number , shift_lsr: 2)
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add( number , number , number , shift_lsr: 4)
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add( number , number , number , shift_lsr: 8)
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add( number , number , number , shift_lsr: 16)
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mov( number , number , shift_lsr: 3)
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add( tmp , number , number , shift_lsl: 2)
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sub( remainder , remainder , tmp , shift_lsl: 1 , update_status: 1)
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add( number , number, 1 , condition_code: :pl )
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add( remainder , remainder , 10 , condition_code: :mi )
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end
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end
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def syscall block , num
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# This is very arm specific, syscall number is passed in r7, other arguments like a c call ie 0 and up
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sys = Virtual::Integer.new( Virtual::RegisterReference.new(SYSCALL_REG) )
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ret = Virtual::Integer.new( Virtual::RegisterReference.new(RETURN_REG) )
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block.add_code mov( sys , num )
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block.add_code swi( 0 )
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#todo should write type into r1 according to syscall
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ret
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end
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end
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end
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