[PATCH] [ARM] Align stack objects passed to functions

[hfinkel at anl.gov]

In http://reviews.llvm.org/D7908#136944, @john.brawn wrote:

> In http://reviews.llvm.org/D7908#136838, @hfinkel wrote:
>
> > You're currently doing this only for pointers that are captured as call arguments. Do you care about pointers captured in any other way (by having their address stored somewhere, or returned, for example)?
>
>
> Maybe? The original patch did that as it just aligned everything that was used in a FrameIndex instruction. I guess the question is, how much do we care if we over-align things pointlessly? When it's an argument to a memcpy call it's definitely a good idea, but in an argument to some other call or when the address is stored somewhere it may turn out to be pointless (which is possibly an argument that I should be restricting this to only memcpy/move etc. calls).


Agreed.

I don't have a strong opinion here. I suppose I'm inclined to go for other kinds of captures as well, or to stick with just memcpy/move/set. Picking only function calls, which amounts to some, but not all, captures, seems like an inconsistency likely to cause different kinds of abstractions to get different optimizations, and that's likely not good. Let's go to one extreme or the other ;)


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