Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.glorb.com!news-out.readnews.com!news-xxxfer.readnews.com!news.misty.com!news.iecc.com!.POSTED!nerds-end From: "Jonathan Thornburg" Newsgroups: comp.compilers Subject: Re: Green Compiler ? Date: 2 Jan 2013 04:09:15 GMT Organization: Compilers Central Lines: 27 Sender: johnl@iecc.com Approved: comp.compilers@iecc.com Message-ID: <13-01-003@comp.compilers> References: <12-12-010@comp.compilers> <12-12-012@comp.compilers> <12-12-022@comp.compilers> <12-12-028@comp.compilers> <12-12-034@comp.compilers> <12-12-037@comp.compilers> <13-01-002@comp.compilers> NNTP-Posting-Host: news.iecc.com X-Trace: leila.iecc.com 1357146470 8114 64.57.183.58 (2 Jan 2013 17:07:50 GMT) X-Complaints-To: abuse@iecc.com NNTP-Posting-Date: Wed, 2 Jan 2013 17:07:50 +0000 (UTC) Keywords: architecture, performance Posted-Date: 02 Jan 2013 12:07:50 EST X-submission-address: compilers@iecc.com X-moderator-address: compilers-request@iecc.com X-FAQ-and-archives: http://compilers.iecc.com Xref: csiph.com comp.compilers:826 George Neuner wrote: >>But registers are a very scarce resource, so that frequent loading from >>memory is hardly avoidable. > > My opinions are colored by experience with DSPs, but I have long > thought that it would be helpful to have a few K-words of non-cache > scratchpad memory very close (1..2 cycles) to the CPU. The Cray-2 and Cray-3 had this (I think they called it "local memory"). Alas, compilers had a lot of trouble making good use of it. As John McCalpin put it in 1998 (at the time he was at SGI): # Local memories work fine if an experience performance person gets # to rewrite the code. It gets a lot more difficult if you have # to educate a compiler to do the right thing.... I don't know if compilers have improved significantly in this area. And on the hardware side, you'd have to figure out what to do on context switch... -- -- "Jonathan Thornburg [remove -animal to reply]" Dept of Astronomy, Indiana University, Bloomington, Indiana, USA "C++ is to programming as sex is to reproduction. Better ways might technically exist but they're not nearly as much fun." -- Nikolai Irgens [It sounds like if we keep working, we might reinvent register windows. -John]