The & (address) operator and register allocation

[Henry Spencer]

In article <9048 at smoke.BRL.MIL> gwyn at brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>... As it now stands (without "noalias"), a
>conforming implementation must make a worst-case assumption and
>handle possible aliasing correctly...

Unless one indicates, in some implementation-dependent way, that it's
not an issue, of course.  Compiler options, #pragma (as near as I can
tell at first glance, the October draft has not outlawed the can-change-
semantics interpretation of #pragma), whatever...

>Registers also have memory addresses on some architectures, for example
>DEC PDP-11.  I've never heard of a compiler exploiting this.

On the 11, it can't, because the registers don't *really* have memory
addresses.  Those "addresses" are good only for use from the front panel,
or emulation thereof.  They don't necessarily work for programs.
-- 
SunOSish, adj:  requiring      |     Henry Spencer at U of Toronto Zoology
32-bit bug numbers.            | uunet!attcan!utzoo!henry henry at zoo.toronto.edu