R12 is callee-saved for A- and R- class interrupt handlers

[Oliver Stannard]

Hi all,

 

For v7A and v7R, r12 must be callee-saved by interrupt handlers. This is
because it is the intra-procedure-call scratch register, which may be
clobbered by any branch subject to a relocation supporting interworking or
long branches (AAPCS, 5.3.1.1, "Use of IP by the linker"). R12 may be used
as a temporary register between function calls, so it must be preserved by
an interrupt handler. It seems that this is mostly implemented, but there
was a bug in the prologue/epilogue generator which prevented it from being
included in the push and pop instructions. The attached patch fixes this.

 

Oliver
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