On Wed, Mar 11, 2015 at 9:58 AM, Mike Shaw <quick...@gmail.com> wrote: > > On Wed, Mar 11, 2015 at 10:49 AM, John McKown <john.archie.mck...@gmail.com> > wrote: > >> Given some of the new instructions, such as LGZR, I wish IBM would >> publish a manual with a title like: "What were the architects thinking >> of? Explanation of the reasons behind the instructions in the z >> architecture". >> ... >> > > "To make the code compiled by the C/C++ compiler and/or WebSphere / Java > code run faster" is the answer to ANY "Why?" question about new > instructions, IMHO...
OK, but I guess that I'm just too dense to understand why that code needs a LGZR instead of simply doing something like: LG Rx,GRANDE NILL Rx,X'FF00' Granted the latter is longer and slower, with a register interlock. But is it used so often that a new instruction is needed? So maybe I am wondering if IBM might publish some of the internal finds on relative use of code sequences, such as the above, which determine the viability of moving them into the firmware. > > > Mike Shaw > MVS/QuickRef Support Group > Chicago-Soft, Ltd. -- He's about as useful as a wax frying pan. 10 to the 12th power microphones = 1 Megaphone Maranatha! <>< John McKown
