Supervisor assisted linkage saves 64 bit registers. If yours is a main routine and not a subroutine called by other routines, then you likely don't need to worry. If you are worried, you might want to consider using the BAKR instruction because it saves the entire 64 bit registers in the linkage stack. Otherwise, you'd need to look at the passed in save area to see if you were supplied with one which has room for the upper half of the registers. Personally, be a lazy slob, I'd use BAKR.
Use of the G instructions is totally independent of the AMODE. So you can use 64 bit registers for data in any AMODE. And also, just switching to AMODE(64) does not make instructions such as L and MR all of a sudden work with 64 bit registers. They still just use the lower fullword of the register. That is, they are non-modal. Other instructions are modal sensitive and say so in the description. -- John McKown Systems Engineer IV IT Administrative Services Group HealthMarkets(r) 9151 Boulevard 26 * N. Richland Hills * TX 76010 (817) 255-3225 phone * [email protected] * www.HealthMarkets.com Confidentiality Notice: This e-mail message may contain confidential or proprietary information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. HealthMarkets(r) is the brand name for products underwritten and issued by the insurance subsidiaries of HealthMarkets, Inc. -The Chesapeake Life Insurance Company(r), Mid-West National Life Insurance Company of TennesseeSM and The MEGA Life and Health Insurance Company.SM > -----Original Message----- > From: IBM Mainframe Assembler List > [mailto:[email protected]] On Behalf Of Joe Owens > Sent: Monday, April 04, 2011 7:01 AM > To: [email protected] > Subject: Re: Best way to multiply doublewords? > > Thanks for the replies, much appreciated. > We do have current processors, just my knowledge that is out > of date :) > > The factor might not be a whole number, which is why I > thought of FP, but > I can see I can follow the multiply by a 64 bit divide by 100 to get a > percentage. > > I take it the 'G' instructions can be executed in 31 bit, due to their > explicit naming (and no-one mentioned amode)? > One question occurs - must I now use extended save areas, as > I am doing > something to the top halves of the GPRs, or will the system > take care of > that for me? (There are no amode 64 progs on the calling chain). > > Thanks, Joe > >
