Path: csiph.com!weretis.net!feeder6.news.weretis.net!news.misty.com!news.iecc.com!.POSTED.news.iecc.com!nerds-end From: gah4 Newsgroups: comp.compilers Subject: Re: Looking for a garbage collection paper Date: Thu, 29 Sep 2022 23:56:42 -0700 (PDT) Organization: Compilers Central Lines: 21 Sender: news@iecc.com Approved: comp.compilers@iecc.com Message-ID: <22-09-023@comp.compilers> References: <22-09-011@comp.compilers> <22-09-012@comp.compilers> <22-09-013@comp.compilers> <22-09-014@comp.compilers> <22-09-016@comp.compilers> <22-09-022@comp.compilers> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="16871"; mail-complaints-to="abuse@iecc.com" Keywords: architecture, history, comment Posted-Date: 30 Sep 2022 21:31:52 EDT X-submission-address: compilers@iecc.com X-moderator-address: compilers-request@iecc.com X-FAQ-and-archives: http://compilers.iecc.com In-Reply-To: <22-09-022@comp.compilers> Xref: csiph.com comp.compilers:3175 On Thursday, September 29, 2022 at 9:40:59 PM UTC-7, gah4 wrote: (snip) > But not if index registers are different from other registers, like > (if I remember) they are on the 7090. > [Yes, the 704 series had separate index registers. It occurs to me that > another way to do this is to use the rotate instructions the 70x and PDP-6/10 > had. Since the word is 36 bits, you rotate by 12 each time and you'll have > three bit patterns. -John] or a ROTC double word rotate on the PDP-10 by 24, with 18 bit addressing and indexing. I am not sure about rotate on the 709 or 7090. Also, for those machines, I suspect a 12 bit shift or rotate takes 12 cycles. They didn't have enough logic for a barrel shifter, like many machines now have. Might be slower than more than one fast instruction. [The 709x had a rotate instruction but this archaeology is a bit far from compilers. -John]