[PATCH] D17000: [AArch64] Reduce number of callee-save save/restores.

[Tim Northover via llvm-commits]

t.p.northover added a comment.

Hi Geoff,

> I assume these MachO fast unwind restrictions also would prevent doing non-leaf frame pointer elimination and redzone optimization.


We'd probably want to keep non-leaf frame pointers independently of unwinding (people are very keen on getting good backtraces here). Similarly, we'd have to check our libc (etc) for red zone violations before it could be turned on.

Are you thinking of using the red zone for callee-saved registers too? That might have unwinding implications.

> Do you think these restrictions are currently captured in the tests that I modified?


I think I should probably specifically write a few basic compact unwind codegen functions which would have broken with your patch. Just a sort of smokescreen to catch obvious things that should be using the compact format. I'll do that today (hopefully).

Cheers.

Tim.


http://reviews.llvm.org/D17000