Re: C compiler pointer management on DSPs

From	robin51@dodo.com.au
Newsgroups	comp.compilers
Subject	Re: C compiler pointer management on DSPs
Date	2020-02-28 10:26 +1100
Organization	Compilers Central
Message-ID	<20-02-025@comp.compilers> (permalink)
References	(4 earlier) <19-09-009@comp.compilers> <19-09-015@comp.compilers> <19-09-017@comp.compilers> <19-09-018@comp.compilers> <20-02-024@comp.compilers>

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On 2020-02-28 09:23, gah4@u.washington.edu wrote:

> Machines not so well designed require masking off the appropriate
> bits before operating with them, though many machines ignore high
> bits on shift operations.  (The 8086 allows shifts up to 255 bits.)

Who can say that the CDC machines (7600; 70 series, etc) were not
well designed?

They were intended to be fast, and to carry out operations on
words (of 60 bits).

To be sure, it was necessary to mask bits (usually characters),
but there was a simple instruction(s) to generate a mask of
n bits (better than loading a word containing bits to be used
as a mask).

On the other hand, the IBM S/360 was designed from the beginning to
handle bytes of 8 bits, half-words of 16 bits, and words of 32 bits.

Instructions could load and store a byte into/from the low-order
bits of a register, without affecting the other bits.  Later models
could load/store one or more bytes into/from a register without
affecting the other bits.

For more general work, masking operations were available in the
32-bit registers.

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PR1ME C compiler sources "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2019-09-25 15:27 +0100
  Re: PR1ME C compiler sources arnold@skeeve.com (Aharon Robbins) - 2019-09-25 18:32 +0000
    Re: PR1ME C compiler sources drb@ihatespam.msu.edu (Dennis Boone) - 2019-09-25 20:02 -0500
      Re: PR1ME C compiler sources arnold@skeeve.com (Aharon Robbins) - 2019-09-26 10:57 +0000
    Re: PR1ME C compiler sources drb@ihatespam.msu.edu (Dennis Boone) - 2019-09-25 20:04 -0500
      Re: PR1ME C compiler sources drb@ihatespam.msu.edu (Dennis Boone) - 2019-09-25 20:28 -0500
        Re: PR1ME C compiler sources "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2019-09-26 11:53 +0100
          Re: PR1ME C compiler sources drb@ihatespam.msu.edu (Dennis Boone) - 2019-09-27 10:19 -0500
            Re: PR1ME C compiler sources "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2019-09-28 00:48 +0100
              Re: PR1ME C compiler pointer management drb@ihatespam.msu.edu (Dennis Boone) - 2019-09-28 11:08 -0500
                Re: PR1ME C compiler sources and pointer formats Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2019-09-29 07:48 -0400
                Re: PR1ME C compiler sources and pointer formats drb@ihatespam.msu.edu (Dennis Boone) - 2019-09-30 22:10 -0500
          Re: PR1ME C compiler sources George Neuner <gneuner2@comcast.net> - 2019-09-27 20:56 -0400
            Re: C compiler pointer management on DSPs "Derek M. Jones" <derek@_NOSPAM_knosof.co.uk> - 2019-09-28 19:19 +0100
              Re: C compiler pointer management on DSPs David Brown <david.brown@hesbynett.no> - 2019-09-29 10:53 +0200
                Re: C compiler pointer management on DSPs Kaz Kylheku <847-115-0292@kylheku.com> - 2019-09-30 23:50 +0000
                Re: C compiler pointer management on DSPs George Neuner <gneuner2@comcast.net> - 2019-10-03 01:34 -0400
                Re: C compiler pointer management on DSPs gah4@u.washington.edu - 2020-02-27 14:23 -0800
                Re: C compiler pointer management on DSPs robin51@dodo.com.au - 2020-02-28 10:26 +1100
                Re: C compiler pointer management on DSPs gah4@u.washington.edu - 2020-02-28 02:33 -0800

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