[Libre-soc-bugs] [Bug 238] POWER Compressed Formal Standard writeup

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Sun Nov 22 02:08:57 GMT 2020


--- Comment #53 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Jacob Lifshay from comment #52)
> Some additional details: For PowerPC64, most functions will have a
> statically-sized stack frame, which allows using offsets from r1 for all
> stack frame memory access. The only code that uses r31 is code that has a
> variable-size stack frame (or where the compiler just doesn't know -- like
> the unoptimized code linked above). Therefore, I think we shouldn't have
> special compressed instructions just for the frame pointer, but I do think
> we should have the frame pointer included in the registers usable by
> compressed instructions.

r31 can be used as a temporary register as well, so it's not like we're wasting
a compressed register slot.

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