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assemblyarmcpu-registers

ARM Assembly - what's the difference between v1 and a1 registers?

I'm currently playing around with the arm simulator called armulator. While looking at some small programs I see registers v1 and a1 being used. What's the difference between the two?

Solution

  • I'm going to assume you're really asking "what do the 'a' and 'v' mean?", and answer that instead.

    The procedure call standard designates some registers as being primarily for "arguments" and "variables", and permits referring to them as such by synonyms:

    register  synonym
 r0        a1
 r1        a2
 r2        a3
 r3        a4
 r4        v1
 r5        v2
 r6        v3
 r7        v4
 r8        v5
 r9        v6
 r10       v7
 r11       v8