[TUHS] Early Unix function calls: expensive?

Clem Cole clemc at ccc.com
Wed Jan 6 03:42:00 AEST 2016

On Tue, Jan 5, 2016 at 11:46 AM, John Cowan <cowan at mercury.ccil.org> wrote:

> A PDP-11 Fortran compiler could have followed such a subroutine call by
> a series of branch instructions and had the callee use MARK rather than
> RTS to return to the correct point in the jump table.

Could be - I was not there for that one but, I'll have to try to ask one or
two of the designers of the the 11 FTN compiler back end when I see them
next who was. Rich or Dave might know/remember.   That said, some of the
folks on the simh mailing list might also remember like Tim or Bob.

That said, IIRC the PDP-11 on chip did not support it, so I suspect the FTN
compiler did not use it.  I also know that in the past, when we had talked
about some of the silly instructions that were created in different ISPs
during lunch conversations, I have specific memories of some of the
compiler folks saying they could never figure out PDP-11's MARK either -
hence my comment about few did know how to put it to good use.
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