Re: ARM stack alignment on hand called functions

["Kris Warkentin" <kewarken at qnx dot com>]

----- Original Message -----
From: "Richard Earnshaw" <rearnsha@arm.com>
> No, I don't think this is correct, since it will mean that the structure
> starts at an unaligned address.  Instead the space allocated for the
> structure on the stack should be rounded up to a word and then the
> structure copied into that space with an aligned starting point.

But in this case, the issue isn't with passing arguments but rather with
returning them.  Earlier in hand_function_call() (in valops.c), there is
some code where if a structure is being returned, we enlarge the stack by
the size of the structure.  This is what wasn't aligned.  For example, if
you called 'fun2()', which returns a 2 byte structure, the type length was
'2' which is how much the stack pointer is out.  This way, when we write the
stack at the start of the called function, our sp is misaligned.  The frame
pointer is fine so the function gets the arguments alright, it's just
writing stack variables and return values to the stack that is buggered.
I'm looking at this and thinking, it just gives a little padding on the
stack to maintain alignment.

cheers,

Kris