Re: C compiler pointer management on DSPs

George Neuner <gneuner2@comcast.net>
Thu, 03 Oct 2019 01:34:28 -0400

          From comp.compilers

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Re: C compiler pointer management on DSPs david.brown@hesbynett.no (David Brown) (2019-09-29)
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Re: C compiler pointer management on DSPs gneuner2@comcast.net (George Neuner) (2019-10-03)
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From: George Neuner <gneuner2@comcast.net>
Newsgroups: comp.compilers
Date: Thu, 03 Oct 2019 01:34:28 -0400
Organization: A noiseless patient Spider
References: 19-09-003 19-09-004 19-09-006 19-09-007 19-09-009 19-09-015 19-09-017 19-09-018
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Keywords: C, architecture
Posted-Date: 04 Oct 2019 11:27:33 EDT

On Sun, 29 Sep 2019 10:53:35 +0200, David Brown
<david.brown@hesbynett.no> wrote:


>I can't think of any application where 48-bit would such a natural fit
>that you'd have it as your basic access unit. Some video DSP's have
>used 48-bit units, but that is for a vector of 3 16-bit colour units.


Analog Devices SHARC series floating point DSPs had 48-bit
instructions and 40-bit extended precision floats aligned at 48-bit
addresses (probably to use the same address generator as for code).


Nominally, though, it was a 16/32 bit device: integer data, including
chars could be 16 or 32 bits, and ordinary (single precision) floats
were 32 bits.


Admittedly, I never encountered any use for the extended floats, but I
assumed they were there for a reason.


YMMV,
George


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