Register contents that are a multiple of 4 are all of the form xxxxx...xx00
Inclusive ORing such a value with the mask 11111...1100 and testing the result for equality with this same mask then yields a simple, low-overhead test for a multiple-of-four value. --jg On 8/27/12, McKown, John <john.mck...@healthmarkets.com> wrote: > Thanks for the technique. I'm not sure that I like the NILL instruction at > this point. It could change an "invalid" (as in "not planned for") RC into a > "valid" RC. Looks like maybe I could use TMLL to just test. (TMLL > R15,X'000C') > > -- > John McKown > Systems Engineer IV > IT > > Administrative Services Group > > HealthMarkets(r) > > 9151 Boulevard 26 * N. Richland Hills * TX 76010 > (817) 255-3225 phone * > john.mck...@healthmarkets.com * 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:ASSEMBLER- >> l...@listserv.uga.edu] On Behalf Of Martin Truebner >> Sent: Monday, August 27, 2012 8:15 AM >> To: ASSEMBLER-LIST@LISTSERV.UGA.EDU >> Subject: Re: which instructions should I use? >> >> John, >> >> >> you still need base+displacement .... desire for an index register; >> >> They come in most cases when there is space in the nibbles for it. But >> for the case you cited there is no need to cover code in >> "procedure division" with a base. (Dynamic storage and literalpool >> do have a base!) -Here is how: >> >> CALL PROGRAM,(PARM1,PARM2),VL >> CHI R15,=Y(MAXENTRIES) >> JH INVALID_RC >> L R15,=A(RC0,RC4,RC8,RCC)(R15) >> BR R15 >> >> Your addon (check for a valid rc) could also be done with this >> >> NILL R15,X'000C' >> >> as a result you only have valid combinations left over (Yes I cheated >> and added an entry for C). >> >> -- >> Martin >> >> Pi_cap_CPU - all you ever need around MWLC/SCRT/CMT in z/VSE >> more at http://www.picapcpu.de >
