Re: "m" constraints, jumps, and alternatives

[H. Peter Anvin]

On 02/20/2014 07:30 PM, Brian Gerst wrote:
> 
> The percpu code uses %P to force absolute addressing mode, instead of
> rip-relative.
> 

   P -- if PIC, print an @PLT suffix.

Clearly it has more effects than that... as the code does reveal:

      /* Avoid (%rip) for call operands.  */
      if (CONSTANT_ADDRESS_P (x) && code == 'P'
          && !CONST_INT_P (x))

That should work... in the probably extremely rare case that any of
these references go to global addresses then they spend an extra byte
(and a little more work during kASLR relocation or module insertion).

	-hpa

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/