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Re: [PATCH 3/4] shallow.c: bit manipulation tweaks

From
Jeff King <peff@peff.net>
Date
Dec 3, 2016, 05:21 UTC
Message-ID
<20161203052104.jbxhzpweupiaz7wi@sigill.intra.peff.net>
In-Reply-To
<1480710664-26290-3-git-send-email-rv@rasmusvillemoes.dk>
On Fri, Dec 02, 2016 at 09:31:03PM +0100, Rasmus Villemoes wrote:
> First of all, 1 << 31 is technically undefined behaviour, so let's just
> use an unsigned literal.

It took me a second to realize that you weren't talking about the unsigned parameter here. You mean using "1U". It might be worth saying:

   ...use an unsigned literal, "1U".
to make it more obvious.
> If i is 'signed int' and gcc doesn't know that i is positive, gcc
> generates code to compute the C99-mandated values of "i / 32" and "i %
> 32", which is a lot more complicated than simple a simple shifts/mask.
Right, that makes sense (though it is a separate issue).
-Peff
Previous: Rasmus VillemoesNext: Rasmus Villemoes
Message 5 of 20 in “shallow.c: make paint_alloc slightly more robust”
  1. 1/4 shallow.c: make paint_alloc slightly more robustRasmus Villemoes, Dec 2, 2016
  2. 2/4 shallow.c: avoid theoretical pointer wrap-aroundRasmus Villemoes, Dec 2, 2016
  3. Jeff KingDec 3, 2016
  4. 3/4 shallow.c: bit manipulation tweaksRasmus Villemoes, Dec 2, 2016
  5. Jeff KingDec 3, 2016
  6. 4/4 shallow.c: remove useless testRasmus Villemoes, Dec 2, 2016
  7. Jeff KingDec 3, 2016
  8. Duy NguyenDec 5, 2016
  9. Jeff KingDec 3, 2016
  10. Duy NguyenDec 5, 2016
  11. 0/6 shallow.c improvementsNguyễn Thái Ngọc Duy, Dec 6, 2016
  12. 1/6 shallow.c: rename fields in paint_info to better express their purposesNguyễn Thái Ngọc Duy, Dec 6, 2016
  13. 5/6 shallow.c: bit manipulation tweaksNguyễn Thái Ngọc Duy, Dec 6, 2016
  14. 4/6 shallow.c: avoid theoretical pointer wrap-aroundNguyễn Thái Ngọc Duy, Dec 6, 2016
  15. 6/6 shallow.c: remove useless codeNguyễn Thái Ngọc Duy, Dec 6, 2016
  16. 3/6 shallow.c: make paint_alloc slightly more robustNguyễn Thái Ngọc Duy, Dec 6, 2016
  17. 2/6 shallow.c: stop abusing COMMIT_SLAB_SIZE for paint_info's memory poolsNguyễn Thái Ngọc Duy, Dec 6, 2016
  18. Jeff KingDec 6, 2016
  19. Duy NguyenDec 6, 2016
  20. Junio C HamanoDec 7, 2016

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