As I am led to understand it, under the covers in the millicode MVCL really is a MVC loop. So MVCL is at least slower by the cost of overhead switching into the millicode environment.
That said, and if I was coding anything which I'm not these days, I'd likely do the MVCL and be done with it unless I knew it was a very frequently executed path in the code. Dave Gibney Information Technology Services Washington State University > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Charles Mills > Sent: Tuesday, May 31, 2011 2:02 PM > To: [email protected] > Subject: Re: What is the current feeling for MVC loop vs. MVCL? > > Just my uninformed opinion, but it's hard for me to see how an MVC loop > could be faster. Both are interruptible. (MVC is not but an MVC *loop* is.) > Both update registers (okay, three versus four). > > I know microcode is not magic but gee, if MVC were faster than whatever > MVCL > does, wouldn't the microcode writers just have used an MVC loop instead of > what they did use for MVCL? > > My uninformed opinion is that MVCL worst case should be no slower than an > MVC loop for indeterminate length moves of possibly more than 256 bytes > (and > as a side benefit, it is a heck of a lot easier to use in that situation, > unless you happen to be very short on spare registers). > > Charles > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf > Of Mike Schwab > Sent: Tuesday, May 31, 2011 1:35 PM > To: [email protected] > Subject: Re: What is the current feeling for MVC loop vs. MVCL? > > How about a macro to replace MVCL with a loop using the same registers but > using MVC? Anyone ever write one? > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] 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 [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
