bs@linus.UUCP (Robert D. Silverman) (01/20/87)
There is some ongoing discussion about register usage in programs. While it is true that one generally wants to keep as many variables as possible (especially such things as loop indices!) there are times when using a lot of registers can actually slow things down. This arises when a subroutine shares registers in common with its parent. If the routine is called many times the cost of saving and restoring registers during the call and return can offset any speed savings thru register usage. I have actually seen this phenomenon occur quite strikingly in programs that require multi-precision arithmetic. The cost of saving the registers for a multi-precise add or multiply routine (say) when they are called ~10^8 or 10^9 times can greatly slow down a program. Bob Silverman