Xref: utzoo comp.arch:7439 comp.lang.c:14500 Newsgroups: comp.arch,comp.lang.c Path: utzoo!henry From: henry@utzoo.uucp (Henry Spencer) Subject: Re: The & (address) operator and register allocation Message-ID: <1988Dec4.004143.1630@utzoo.uucp> Organization: U of Toronto Zoology References: <1224@cps3xx.UUCP> <9048@smoke.BRL.MIL> Date: Sun, 4 Dec 88 00:41:43 GMT In article <9048@smoke.BRL.MIL> gwyn@brl.arpa (Doug Gwyn (VLD/VMB)) 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@zoo.toronto.edu