How to change assembly language loop part into binary code?

Question

On two pass assembler, if there is assembly code like

test     start   1000
first    lda     index
         ldx     index
read     jsub    strcpy
         ldch    str,x
         comp    eof
         jeq     end
         lda     index
         add     one
         sta     index
         ldx     index
         j       read  
strcpy   td      indev
         jeq     strcpy
         rd      indev
         stch    str,x
         rsub
end      lda     index
index    word    0
one      word    1
str      resw    5
indev    byte    x'f3'
eof      byte    x'000004'
         end     first

how can I change it to binary code? especially that jump part? Are binary codes in loop section repeated as many time as loop actually executed?

If you want assemble-time loop unrolling, use assembler macros, not runtime branch instructions. e.g. in NASM, %rep 4 / ... / %endrep. — Peter Cordes
– Peter Cordes, Commented May 5, 2018 at 14:22

Paul Childs · Accepted Answer · 2018-05-05 07:24:36Z

2

Of course not. What if you had no a priori knowledge of how many times it will be needed? Each label will be an address in memory of the code. The assembler converts these labels into addresses. The jump gets converted into a binary machine code like all other statements in assembler.

answered May 5, 2018 at 7:24

Paul Childs

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