[AARCH64] question about RELA relocations
Sun Jan 31 17:04:00 GMT 2016
On Tue, Jan 12, 2016 at 11:56:43AM +0000, Jiong Wang wrote:
> gcc combine should have combined:
> add x0, x0, :lo12:.LANCHOR0
> ldr x0, [x0,8]
> ldr x0, [x0,#:lo12:.LANCHOR0+8]
> It's not happen because combine pass invoked "init_recog_no_volatile" to
> prevent volatile memory to be combined. I guess combine is too
> conservative on this, purely combine contant offsets inside volatile
> memory should be safe. (CCed Segher).
[ For some reason I didn't see this mail before, sorry about that. ]
This is a well-known issue, see PR60749, PR50677, PR49807, likely more.
Simply allowing volatile refs is not conservative enough. Backends can
use a workaround like the msp430 port does, for those cases where it knows
it will work.
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