From mboxrd@z Thu Jan 1 00:00:00 1970 From: clemc@ccc.com (Clem Cole) Date: Tue, 5 Jan 2016 12:42:00 -0500 Subject: [TUHS] Early Unix function calls: expensive? In-Reply-To: <20160105164642.GA20786@mercury.ccil.org> References: <20160103233543.GA10102@minnie.tuhs.org> <76BC99D5-A8C4-4F8B-8D7D-C621CBD18238@tfeb.org> <20160104000113.GD1602@mercury.ccil.org> <328D91D8-FF74-46EE-A281-5432716E6206@ieee.org> <418F9945-C1BC-4EA1-85F3-981342A9BDD6@ronnatalie.com> <20160105164642.GA20786@mercury.ccil.org> Message-ID: On Tue, Jan 5, 2016 at 11:46 AM, John Cowan 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. -------------- next part -------------- An HTML attachment was scrubbed... URL: