Re: [Amforth-devel] Assembler - initial issues or bugi

[Marcin C. <sa...@sa...>]

On Wed, 8 Sep 2010, pito wrote:

> A version with unused registers, crashes (anforth 4.0,
> assembler.frt).
>
> \ Manual v 4.0 : The registers from R10 to R13 are currently unused,
>
> \ but may be used for the VM extended registers X and Y sometimes.
>
> code ++_ \ ( x1 x2 x3 -- x4 )

Looking at my assembly listing:

             .def temp0 = r16
             .def temp1 = r17
             .def tosl = r24
             .def tosh = r25

           PFA_PLUS:
C:0039ab 9109          ld temp0, Y+
C:0039ac 9119          ld temp1, Y+
C:0039ad 0f80          add tosl, temp0
C:0039ae 1f91          adc tosh, temp1
C:0039af ce5e          rjmp DO_NEXT

So, that means that simple
 		  	ld temp0, Y+
 		  	ld temp1, Y+
 			add tosl, temp0
 			adc tosh, temp1
 			ld temp0, Y+
 		  	ld temp1, Y+
 			add tosl, temp0
 			adc tosh, temp1
 			rjmp DO_NEXT

should do the trick. Doing in Forth:

R16 constant temp0
R17 constant temp1
R24 constant tosl
R25 constant tosh

code ++_
 	temp0 Y+ ld,
 	temp1 Y+ ld,
 	tosl temp0 add,
 	tosh temp1 adc,
 	temp0 Y+ ld,
 	temp1 Y+ ld,
 	tosl temp0 add,
 	tosh temp1 adc,
end-code

hex
1000 100 10 ++_  .
1110  ok

1111 222 33 ++_ .
1366  ok

It's really beneficial to study existing assembler
code! It also is immediately clear that ++_ is 
the equivalent of + + - what I did is just + operation
inlined twice.

--Marcin