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assemblyarm

What is the purpose of putting an immediate value in parens in ARM assembly?

What, if anything, is the difference between these two instructions?

subs    r2, r2, #(32)

subs    r2, r2, #32

What are the parentheses () for?

Solution

  • Actually, those are parentheses, not brackets.

    There is no difference between:

    subs    r2, r2, #(32)

    and

    subs    r2, r2, #32

    I suspect the (32) used to be something like (32 - 8) or something that was interesting / meaningful / necessary at the time, then the "- 8" was removed but the parentheses were simply kept since they do no harm.

    For the sake of completeness, even though it's not what you asked & you probably already know it:

    The code

    LDR r0, [r1]

    with "brackets" (register indirect) loads r0 with the value whose address is stored in r1 -- in other words, if r1 holds 1000, r0 will be loaded from MEM[1000]