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From: dds@cc.ic.ac.uk (Diomidis Spinellis)
Newsgroups: comp.compilers
Subject: Re: Register Allocation
Keywords: Pointers
Message-ID: <1990Feb28.051730.5340@esegue.segue.boston.ma.us>
Date: 28 Feb 90 05:17:30 GMT
References: <1990Feb20.155619.3121@esegue.segue.boston.ma.us> <1990Feb24.210757.4202@esegue.segue.boston.ma.us>
Sender: compilers-sender@esegue.segue.boston.ma.us
Reply-To: dds@cc.ic.ac.uk (Diomidis Spinellis)
Organization: Imperial College Department of Computing
Lines: 34
Approved: compilers@esegue.segue.boston.ma.us

In article <1990Feb24.210757.4202@esegue.segue.boston.ma.us> cik@l.cc.purdue.edu (Herman Rubin) writes:
>In article <1990Feb20.155619.3121@esegue.segue.boston.ma.us>, napi@rangkom.MY (Mohd Hanafiah b. Abdullah) writes:
>> How does one perform register allocation on scalar variables that may
>> be pointed to by others?
[...]
>and I have no difficulty using machine language.  The only mainframes whose
>instruction set I have known which are appropriately set up in hardware for
>this are the long obsolete UNIVAC 1108 and 1110. 
[...]
>[The PDP-10/DEC-20 has addressable registers as well, but as pointed out
>elsewhere that's only a small part of the problem.  As soon as you call
>another routine, it's liable to save the register and put something else
>there, and you lose.  -John]

Addressing registers is possible in the Texas Instruments TM 990 series
of minis and TMS-9900, TMS-9950 microprocessors.  All 16 general
purpose registers are in a memory block pointed by a single processor
register the workspace pointer.  With some care one can implement
register windowing.  Saving the registers is then just a change of the
workspace pointer; pointers that point to registers in previous stack
frames still point to the correct object.  On the 9995 the registers can
be located on on-chip RAM, so the performance is not affected by the cost
of external memory accesses.

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Diomidis Spinellis                  Internet:                 dds@cc.ic.ac.uk
Department of Computing             UUCP:                    ...!ukc!iccc!dds
Imperial College                    JANET:                    dds@uk.ac.ic.cc
London SW7 2BZ

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