CODEWITHSUNDEEP
assemblymacrosx86-64gnu-assembler
BinaryBurst
BinaryBurst

Reputation: 139

How can I concatenate a label not in a macro definition? (in GAS assembler)

I want to do this:

i=0
.rept 3
    add rcx,[a?(i*2+1)]
    i=i+1
.endr

It should output this:

add rcx,[a1]
add rcx,[a3]
add rcx,[a5]

I can't find any solution to this problem. I don't want it to be inside a macro definition.

Upvotes: 2

Views: 761

Answers (1)

Michael Petch
Michael Petch

Reputation: 47593

I do not believe you can solve this without using macros or some other type of pre-processing. The GNU assembler method of doing this could look something like:

.altmacro

.macro addmac val
    add rcx, [a\val]
.endm

.macro loopmac
    i=0
    .rept 3
        addmac %(i*2+1)
        i=i+1
    .endr
.endm

You then use the loopmac macro like this:

loopmac

You'll need the .altmacro directive to be able to process %(i*2+1) properly:

7.4 .altmacro

You can write ‘%expr’ to evaluate the expression expr and use the result as a string.

Rather than using .rept you could use .irp and simplify the macro to:

.macro loopmac
    .irp i,1,3,5
        add rcx, [a\i]
    .endr
.endm

The last example doesn't need .altmacro processing.

Upvotes: 2

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