patchAVR C Runtime Library - Patches: patch #10101, util/crc16.h: improved...


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patch #10101: util/crc16.h: improved _crc_xmodem_update (smaller & faster)

Submitter:  Benoit Steinmetz <sten>
Submitted:  Sun 29 Aug 2021 09:20:55 PM UTC
Category:  None Priority:  5 - Normal
Status:  None Privacy:  Public
Assigned to:  None Open/Closed:  Open

Sun 29 Aug 2021 09:20:55 PM UTC, original submission:  

The attached patch improves the _crc_xmodem_update algorithm.  The improved algorithm uses 14 instructions instead of the original 25.  Additionally the temporary variables have less strict constraints (=r instead of =d), and r0 is not clobbered.

I have successfully tested the new algorithm with all possible inputs (65536 * 256) against the original algorithm.  The test was run in simulavr.  See attached files main.c, orig_crc.c and

Benoit Steinmetz <sten>


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Attached Files
file #51831:  main.c added by sten (1KiB - text/x-csrc)
file #51832:  orig_crc.c added by sten (116B - text/x-csrc)
file #51833: added by sten (51B - application/x-sh)


Depends on the following items: None found

Items that depend on this one: None found


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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2021-08-29 sten Attached File- Added patch_crc_xmodem_update.txt, #51830
        Attached File- Added main.c, #51831
        Attached File- Added orig_crc.c, #51832
        Attached File- Added, #51833

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