Bill Frantz wrote:
In C, each separately compiled routine must re-load it from its memory location because they can not coordinate register usage.
There are such things as global optimizers that are quite capable of locating heavily-used global variables.
Another place where this global view of a program helps is in re-loads after calling externally compiled routines. The compiler must assume that the external routine has changed the variable
No, it's not true that it "must" do that. There are optimizer systems that defer decisions until link time (the MIPS compilers for example). That said, it's probably the case that a hand-written DES routine could probably better a good optimizer; the size of the problem is pretty small. On the other hand, I suspect a specially-tuned optimizer that used (maybe; I'm making this up off the top of my head) some sort of genetic techniques could find faster code sequences than a human coder would. ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ Mike McNally -- Egregiously Pointy -- Tivoli Systems, "IBM" -- Austin mailto:m5@tivoli.com mailto:m101@io.com http://www.io.com/~m101 ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^