🚀 go-pugleaf

In article ... jwil1@cs.aukuni.ac.nz (TMOTA) writes:

   kers@hplb.hpl.hp.com (Chris Dollin) writes:
   >   And remember that Acorn's C compiler (the ARM proc. call std.?) is clever
   >   enough to notice when you call a function that does not call another (a
   >   leaf function), and does not bother with most of the context-storing
   >   operations involved in normal function calls.

   >I'm not sure you said what you meant. There's no cleverness involved in 
   >calling a leaf function (after all, who's to know that it *is* a leaf 
               				^^^^^^^^^^^^^ Mr. Compiler knows.
   >function?), it's just that leaf functions don't need to carry all the
   > baggage of a full function
   >call -- it's the code of the leaf that ``does not bother with most of the
   >context-storing operations''. [They don't carry the baggage because there's
   >very little that can go wrong inside them, so they don't need to record who
   >they are in case something does.]

   Actually, I thought that they didn't bother stacking anything because the
   compiler *knows* they are leaf-functions. Leaf functions being defined as
   functions which do not call any other functions; this means that you *know*
   the function doesn't call anyone else, so you *know* that you don't need to
   bother with stacking stuff that you would otherwise need to restore context
   on return from a called function.

The compiler knows that a function is a leaf function when it *compiles* it,
not when it compiles a *call* to it (your original remark - at the top - said 
``is clever enough to notice when you call [note this] a function that does not
call another'').

That is, what you *said* suggests that the compiler compiles *calls* to leaf
functions in a special way, and what I think you *meant* is that *leaf
functions* were compiled in a special way.

Otherwise I think we're in furious agreement.

--

Regards,    | "Layered protocols give the software implementor a chance to
Kers.       | ruin his performance in each layer." - Don Gillies