bug#24703: Store references in 8-byte chunks in compiled code

[Leo Famulari]

On Sat, Nov 05, 2016 at 12:15:25AM +0100, Ludovic Courtès wrote:
> I’ve fiddled a bit with GCC and read some code.  No success yet, but
> here’s a status update.

Thanks for writing this out!

> Instead, the knobs we have are (1) global flag to enable/disable each
> built-in function (like -fno-builtin-… does), and (2) an x86-specific
> knob to determine whether to use ‘movabs’ or not (‘-mmemcpy-strategy’
> supposedly controls that, but ‘-mmemcpy-strategy=libcall:-1:noalign’
> doesn’t seem to have any effect for instance.)

Please correct me if I paraphrase the choices incorrectly:
(1) Completely disable the strcpy optimization for all architectures
(2) Ostensibly change how strcpy is optimized on x86, except the knob
seems to have no effect

> These knobs are not great because that would lead us to disable the
> optimization wholesale, which is not desirable.

What are the costs of (1)? Should we report (2) upstream?