Register r9 in the ARM ABI

Niels Möller nisse at
Fri Mar 1 08:41:20 CET 2013

I have a general ARM question, that maybe Richard or someone else on the
list can answer.

>From the ABI documentation I've read, register r9 is in some way
reserved for implementation of things like thread local storage. If I
write a leaf function (not calling anybody else, and not using thread
local storage), can a use r9 like any other callee-save register or not?

The only potential problem case I see is if my function is interupted by
a signal, and the signal handler expects the value in register r9 to be


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