Folks, Again, pardon my interruption. Two aspects (about three words I think) I have to relate is ... pipeline cache and (needless to add), the way the code (sequencing) was written.
Jim Thomas 617-233-4130 (mobile) 636-294-1014 (res) j...@thethomasresidence.us (Email) -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On Behalf Of David Crayford Sent: Tuesday, May 31, 2011 10:32 PM To: IBM-MAIN@bama.ua.edu Subject: Re: What is the current feeling for MVC loop vs. MVCL? On 1/06/2011 12:13 AM, Kirk Wolf wrote: > The IBM C compiler would generate an MVC loop. So, that's how IBM feels I > guess. > And when the length is a constant it generates multiple MVC instructions to eliminate branches. Kind of like loop unrolling. * * char input[528]; * * memcpy( output, input, sizeof input ); MVC (*)void(256,r1,0),input(r4,1508) MVC (*)void(256,r1,256),input(r4,1764) MVC (*)void(16,r1,512),input(r4,2020) And if you increase the size of the buffer it generates a loop with loop unrolling (if that makes sense). There seems to be a HWM where it drops into a loop. * * char input[10000]; * * memcpy( output, input, sizeof input ); LA r0,5 LA r6,2176(r4,) @2L4 DS 0H MVC (*)void(256,r1,0),input(r6,0) MVC (*)void(256,r1,256),input(r6,256) MVC (*)void(256,r1,512),input(r6,512) MVC (*)void(256,r1,768),input(r6,768) MVC (*)void(256,r1,1024),input(r6,1024) MVC (*)void(256,r1,1280),input(r6,1280) MVC (*)void(256,r1,1536),input(r6,1536) LA r1,(*)void(,r1,1792) LA r6,input(,r6,1792) BRCT r0,@2L4 MVC (*)void(256,r1,0),input(r6,0) MVC (*)void(256,r1,256),input(r6,256) MVC (*)void(256,r1,512),input(r6,512) MVC (*)void(256,r1,768),input(r6,768) MVC (*)void(16,r1,1024),input(r6,1024) > Kirk Wolf > Dovetailed Technologies > http://dovetail.com > > On Tue, May 31, 2011 at 8:22 AM, Binyamin Dissen<bdis...@dissensoftware.com >> wrote: >> If the move is for an unknown length but is likely to be less than 256: >> >> Is it worth checking the length for a specific value and proceed with MVC >> loop >> if small enough and MVCL if large? >> >> -- >> Binyamin Dissen<bdis...@dissensoftware.com> >> http://www.dissensoftware.com >> >> Director, Dissen Software, Bar& Grill - Israel >> >> >> Should you use the mailblocks package and expect a response from me, >> you should preauthorize the dissensoftware.com domain. >> >> I very rarely bother responding to challenge/response systems, >> especially those from irresponsible companies. >> >> ---------------------------------------------------------------------- >> For IBM-MAIN subscribe / signoff / archive access instructions, >> send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO >> Search the archives at http://bama.ua.edu/archives/ibm-main.html >> > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO > Search the archives at http://bama.ua.edu/archives/ibm-main.html ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html ----- No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1375 / Virus Database: 1509/3671 - Release Date: 05/31/11 ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
