I understand that LA can cause an "address generation interrupt" in the pipeline on some "z" models and as a rule of thumb, LHI is better to use when you can. Similar nasties occur with things like BCTR Rx,0 (typically used to decrement a register), such that AHI Rx,-1 tends to work better. (In the early look-ahead processing that occurs in the pipeline, the never-branch nature of the BCTR isn't (yet) recognized, only that there is a branch. This stalls the pipeline's pre-processing and parallel execution capabilities until the full nature of the branch is interpreted.
At 11:44 PM 12/12/2007, Rick Fochtman wrote: >------------------------<snip>------------------- > >>Well, just for the sport of it, I think this requires even less >>(not tested): >> >> LHI R1,8 >> IC R2,BYTE >>STC STC R2,RESULT-1(R1) >> SRL R2,1 >> BCT R1,STC >> NC RESULT,=8X'01' >> OC RESULT,=8X'F0' >>* >>BYTE DC B'01110101' Sample input >>RESULT DS CL8 Output >> >> 32 Instructions >> 16 Literals >> 1 Input Area >> 8 Output Area >> >> 57 Total Bytes >> 7 Total Instructions >> >>BTW, John, your second instruction below refers to WORK8, which >>doesn't seem to be defined. >> >-------------------------<snip>--------------------------- >Why not: > > LA R1,8 >instead of > LHI R1,8 > >Inquiring minds want to know....... <G> > ================================================== Art Celestini Celestini Development Services Phone: 201-670-1674 Wyckoff, NJ ============= http://celestini.com ============= Mail sent to the "From" address used in this post will be rejected by our server. Please send off- list email to: ibmmain<at-sign>celestini<dot>com. ================================================== ---------------------------------------------------------------------- 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
