> -----Original Message----- > From: IBM Mainframe Assembler List > [mailto:[email protected]] On Behalf Of David Bond > Sent: Friday, August 20, 2010 8:45 AM > To: [email protected] > Subject: Re: CDS and alignment question > > On Fri, 20 Aug 2010 08:26:28 -0500, McKown, John wrote: > >THEPROG CSECT > > STM 14,12,12(13) > > LR 12,15 > > USING THEPROG,12,11,10 > > LAY 11,4096(,12) > > LAY 10,4096(,11) > > I realize that the STM implies that the program is not in > 64-bit mode, but a > better sequence would be: > LA 12,0(,15) > LAY 11,4096(,15) > LAY 10,4096*2(,15) > > LA is better than LR because it works in any addressing mode > and clears the > non-address bits. Also if R12 is used immediately as a base > register, LA > provides the result to the pipeline faster than LR. And > basing the LAY > instructions off of R15 instead of R12 eliminates the > pipeline stalls caused > by each instruction being dependent on the prior. > > David
Good point on the pipeline. I am constantly forgetting about pipeline delays. -- John McKown Systems Engineer IV IT Administrative Services Group HealthMarkets(r) 9151 Boulevard 26 * N. Richland Hills * TX 76010 (817) 255-3225 phone * (817)-691-6183 cell [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
