89 lines
2.7 KiB
Ruby
89 lines
2.7 KiB
Ruby
module Arm
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class Translator
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# don't replace labels
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def translate_Label code
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nil
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end
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# Arm stores the return address in a register (not on the stack)
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# The register is called link , or lr for short .
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# Maybe because it provides the "link" back to the caller
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# the vm defines a register for the location, so we store it there.
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def translate_SaveReturn code
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ArmMachine.str( :lr , code.register , 4 * code.index )
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end
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def translate_GetSlot code
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# times 4 because arm works in bytes, but vm in words
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ArmMachine.ldr( code.register , code.array , 4 * code.index )
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end
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def translate_RegisterTransfer code
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# Register machine convention is from => to
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# But arm has the receiver/result as the first
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ArmMachine.mov( code.to , code.from)
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end
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def translate_SetSlot code
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# times 4 because arm works in bytes, but vm in words
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ArmMachine.str( code.register , code.array , 4 * code.index )
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end
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def translate_FunctionCall code
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ArmMachine.call( code.method )
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end
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def translate_FunctionReturn code
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ArmMachine.ldr( :pc , code.register , 4 * code.index )
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end
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def translate_LoadConstant code
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constant = code.constant
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if constant.is_a?(Parfait::Object) or constant.is_a? Symbol
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return ArmMachine.add( code.register , constant )
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else
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return ArmMachine.mov( code.register , code.constant )
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end
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end
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# This implements branch logic, which is simply assembler branch
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#
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# The only target for a call is a Block, so we just need to get the address for the code
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# and branch to it.
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def translate_Branch code
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ArmMachine.b( code.block )
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end
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def translate_Syscall code
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call_codes = { :putstring => 4 , :exit => 1 }
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int_code = call_codes[code.name]
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raise "Not implemented syscall, #{code.name}" unless int_code
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send( code.name , int_code )
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end
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def putstring int_code
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codes = ArmMachine.ldr( :r1 , Register.message_reg, 4 * Register.resolve_index(:message , :receiver))
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codes.append ArmMachine.add( :r1 , :r1 , 8 )
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codes.append ArmMachine.mov( :r0 , 1 )
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codes.append ArmMachine.mov( :r2 , 12 ) # String length, obvious TODO
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syscall(int_code , codes )
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end
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def exit int_code
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codes = Register::Label.new(nil , "exit")
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syscall int_code , codes
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end
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private
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# syscall is always triggered by swi(0)
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# The actual code (ie the index of the kernel function) is in r7
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def syscall int_code , codes
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codes.append ArmMachine.mov( :r7 , int_code )
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codes.append ArmMachine.swi( 0 )
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codes
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end
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end
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end
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