[TUHS] Early Unix function calls: expensive?

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Jan 4 22:53:10 AEST 2016

    > that's 28+13 = 41 memory cycles.
    > ...
    > purely in overhead (counting putting the args on the stack as overhead).

Oh, I missed an instruction for de-stacking the arguments, which was typically
something like 'add #N, sp', so another two instruction word fetches, or 43

Ironically, if N=4, the compiler used to emit a 'cmp (sp)+, (sp)+', which is
more efficient space-wise (one word instead of two), but less time-wise
(3 cycles instead of 2).


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