In a message dated 7/14/2005 10:22:13 A.M. Central Daylight Time, [EMAIL PROTECTED] writes:
Might this also depend on whether the storage operand is doubleword aligned, and whether the registers are an even/odd pair? It definitely depends on the alignment of the storage operand. This is one of the 853 variables I mentioned (a slight exaggeration or a SWAG, but there are a LOT of variables). Even/odd pair I don't know about. Wouldn't surprise me. I once heard a rumor that there was special millicode to optimize "STM R14,R12". I missed that rumor, but it could be. IBM invented special opcodes to handle certain very frequently executed functions in MVS and many other software products that run on their mainframes (CP, VS1, e.g.). They were documented in the MVS Assist Feature book, but still not in the z/Arch. Princ. Ops. Too operating system-specific I supposed. E.g., Add FRR is B242 (where was remove FRR?), obtain/release local lock, fix page. The squeaky wheel ought to get more grease than the others. A programmer I know once discovered that (on a 148?) LM; STM moved a doubleword faster than MVC. He accordingly updated all his assembly code. He was livid when we got a Magnusson M80, marketed to compete with the 148, and discovered that MVC was faster than LM; STM. A true Blue partisan, he had to confront the choice of optimizing his code for competing hardware or leaving it suboptimal. He was not in the least soothed that the M80 executed neither instruction slower than the 148. A very good reason not to care or to be partisan. > And in any case "who cares"? Best reason of all. Time saved is in the order of nanoseconds; time spent on discussing, thinking about, different keystrokes, etc., far outweighs the benefit UNLESS the code is executed thousands of times per second in critical paths, like disabled interrupt processors, the Dispatcher, adding FRRs, etc. Bill Fairchild ---------------------------------------------------------------------- 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