Re: Cost of handling misaligned access

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Sujet : Re: Cost of handling misaligned access
De : mitchalsup (at) *nospam* aol.com (MitchAlsup1)
Groupes : comp.arch
Date : 14. Feb 2025, 22:52:39
Autres entêtes
Organisation : Rocksolid Light
Message-ID : <0fc4cc997441e25330ff5c8735247b54@www.novabbs.org>
References : 1 2 3 4 5
User-Agent : Rocksolid Light
On Fri, 14 Feb 2025 21:14:11 +0000, BGB wrote:

On 2/13/2025 1:09 PM, Marcus wrote:
-------------
>
The problem arises when the programmer *deliberately* does unaligned
loads and stores in order to improve performance. Or rather, if the
programmer knows that the hardware supports unaligned loads and stores,
he/she can use that to write faster code in some special cases.
>
>
Pretty much.
>
>
This is partly why I am in favor of potentially adding explicit keywords
for some of these cases, or to reiterate:
   __aligned:
     Inform compiler that a pointer is aligned.
     May use a faster version if appropriate.
       If a faster aligned-only variant exists of an instruction.
       On an otherwise unaligned-safe target.
   __unaligned: Inform compiler that an access is unaligned.
     May use a runtime call or similar if necessary,
       on an aligned-only target.
     May do nothing on an unaligned-safe target.
   None: Do whatever is the default.
     Presumably, assume aligned by default,
       unless target is known unaligned-safe.
It would take LESS total man-power world-wide and over-time to
simply make HW perform misaligned accesses.

Date Sujet#  Auteur
3 Feb 25 * Re: Cost of handling misaligned access106Anton Ertl
3 Feb 25 +- Re: Cost of handling misaligned access9BGB
3 Feb 25 +* Re: Cost of handling misaligned access3Thomas Koenig
3 Feb 25 i`* Re: Cost of handling misaligned access2BGB
3 Feb 25 i `- Re: Cost of handling misaligned access1MitchAlsup1
4 Feb 25 +* Re: Cost of handling misaligned access40Anton Ertl
5 Feb 25 i`* Re: Cost of handling misaligned access39Terje Mathisen
5 Feb 25 i +* Re: Cost of handling misaligned access4Anton Ertl
5 Feb 25 i i+* Re: Cost of handling misaligned access2Terje Mathisen
6 Feb 25 i ii`- Re: Cost of handling misaligned access1Anton Ertl
6 Feb 25 i i`- Re: Cost of handling misaligned access1Anton Ertl
5 Feb 25 i `* Re: Cost of handling misaligned access34Michael S
6 Feb 25 i  +* Re: Cost of handling misaligned access32Anton Ertl
6 Feb 25 i  i`* Re: Cost of handling misaligned access31Michael S
6 Feb 25 i  i +* Re: Cost of handling misaligned access2Anton Ertl
6 Feb 25 i  i i`- Re: Cost of handling misaligned access1Michael S
6 Feb 25 i  i `* Re: Cost of handling misaligned access28Terje Mathisen
6 Feb 25 i  i  `* Re: Cost of handling misaligned access27Terje Mathisen
6 Feb 25 i  i   `* Re: Cost of handling misaligned access26Michael S
6 Feb 25 i  i    `* Re: Cost of handling misaligned access25Terje Mathisen
6 Feb 25 i  i     +* Re: Cost of handling misaligned access19Michael S
7 Feb 25 i  i     i`* Re: Cost of handling misaligned access18Terje Mathisen
7 Feb 25 i  i     i `* Re: Cost of handling misaligned access17Michael S
7 Feb 25 i  i     i  `* Re: Cost of handling misaligned access16Terje Mathisen
7 Feb 25 i  i     i   `* Re: Cost of handling misaligned access15Michael S
7 Feb 25 i  i     i    +- Re: Cost of handling misaligned access1Terje Mathisen
7 Feb 25 i  i     i    +* Re: Cost of handling misaligned access3MitchAlsup1
8 Feb 25 i  i     i    i+- Re: Cost of handling misaligned access1Terje Mathisen
8 Feb 25 i  i     i    i`- Re: Cost of handling misaligned access1Michael S
8 Feb 25 i  i     i    `* Re: Cost of handling misaligned access10Anton Ertl
8 Feb 25 i  i     i     +- Re: Cost of handling misaligned access1Terje Mathisen
8 Feb 25 i  i     i     +* Re: Cost of handling misaligned access6Michael S
8 Feb 25 i  i     i     i`* Re: Cost of handling misaligned access5Anton Ertl
8 Feb 25 i  i     i     i +- Re: Cost of handling misaligned access1Michael S
9 Feb 25 i  i     i     i +* Re: Cost of handling misaligned access2Michael S
11 Feb 25 i  i     i     i i`- Re: Cost of handling misaligned access1Michael S
9 Feb 25 i  i     i     i `- Re: Cost of handling misaligned access1Michael S
9 Feb 25 i  i     i     +- Re: Cost of handling misaligned access1Michael S
10 Feb 25 i  i     i     `- Re: Cost of handling misaligned access1Michael S
7 Feb 25 i  i     `* Re: Cost of handling misaligned access5BGB
7 Feb 25 i  i      `* Re: Cost of handling misaligned access4MitchAlsup1
7 Feb 25 i  i       `* Re: Cost of handling misaligned access3BGB
8 Feb 25 i  i        `* Re: Cost of handling misaligned access2Anssi Saari
8 Feb 25 i  i         `- Re: Cost of handling misaligned access1BGB
6 Feb 25 i  `- Re: Cost of handling misaligned access1Terje Mathisen
6 Feb 25 +* Re: Cost of handling misaligned access5Waldek Hebisch
6 Feb 25 i+* Re: Cost of handling misaligned access3Anton Ertl
6 Feb 25 ii`* Re: Cost of handling misaligned access2Waldek Hebisch
6 Feb 25 ii `- Re: Cost of handling misaligned access1Anton Ertl
6 Feb 25 i`- Re: Cost of handling misaligned access1Terje Mathisen
13 Feb 25 `* Re: Cost of handling misaligned access48Marcus
13 Feb 25  +- Re: Cost of handling misaligned access1Thomas Koenig
14 Feb 25  +* Re: Cost of handling misaligned access41BGB
14 Feb 25  i`* Re: Cost of handling misaligned access40MitchAlsup1
18 Feb 25  i `* Re: Cost of handling misaligned access39BGB
18 Feb 25  i  +* Re: Cost of handling misaligned access33MitchAlsup1
18 Feb 25  i  i+- Re: Cost of handling misaligned access1BGB
18 Feb 25  i  i`* Re: Cost of handling misaligned access31Michael S
18 Feb 25  i  i +- Re: Cost of handling misaligned access1Thomas Koenig
18 Feb 25  i  i +* Re: Cost of handling misaligned access26MitchAlsup1
18 Feb 25  i  i i`* Re: Cost of handling misaligned access25Terje Mathisen
18 Feb 25  i  i i `* Re: Cost of handling misaligned access24MitchAlsup1
19 Feb 25  i  i i  `* Re: Cost of handling misaligned access23Terje Mathisen
19 Feb 25  i  i i   `* Re: Cost of handling misaligned access22MitchAlsup1
19 Feb 25  i  i i    `* Re: Cost of handling misaligned access21BGB
20 Feb 25  i  i i     +- Re: Cost of handling misaligned access1Robert Finch
20 Feb 25  i  i i     +* Re: Cost of handling misaligned access5MitchAlsup1
20 Feb 25  i  i i     i+* Re: Cost of handling misaligned access2BGB
20 Feb 25  i  i i     ii`- Re: Cost of handling misaligned access1BGB
21 Feb 25  i  i i     i`* Re: Cost of handling misaligned access2Robert Finch
21 Feb 25  i  i i     i `- Re: Cost of handling misaligned access1BGB
21 Feb 25  i  i i     `* Re: Cost of handling misaligned access14BGB
22 Feb 25  i  i i      +- Re: Cost of handling misaligned access1Robert Finch
22 Feb 25  i  i i      `* Re: Cost of handling misaligned access12Robert Finch
23 Feb 25  i  i i       +* Re: Cost of handling misaligned access10BGB
23 Feb 25  i  i i       i`* Re: Cost of handling misaligned access9Michael S
24 Feb 25  i  i i       i +- Re: Cost of handling misaligned access1BGB
24 Feb 25  i  i i       i `* Re: Cost of handling misaligned access7Michael S
24 Feb 25  i  i i       i  +* Re: Cost of handling misaligned access4Robert Finch
24 Feb 25  i  i i       i  i+- Re: Cost of handling misaligned access1BGB
24 Feb 25  i  i i       i  i`* Re: Cost of handling misaligned access2MitchAlsup1
25 Feb 25  i  i i       i  i `- Re: Cost of handling misaligned access1BGB
25 Feb 25  i  i i       i  `* Re: Cost of handling misaligned access2MitchAlsup1
25 Feb 25  i  i i       i   `- Re: Cost of handling misaligned access1BGB
23 Feb 25  i  i i       `- Re: Cost of handling misaligned access1Robert Finch
18 Feb 25  i  i `* Re: Cost of handling misaligned access3BGB
19 Feb 25  i  i  `* Re: Cost of handling misaligned access2MitchAlsup1
19 Feb 25  i  i   `- Re: Cost of handling misaligned access1BGB
18 Feb 25  i  `* Re: Cost of handling misaligned access5Robert Finch
18 Feb 25  i   `* Re: Cost of handling misaligned access4BGB
18 Feb 25  i    `* Re: Cost of handling misaligned access3Brett
18 Feb 25  i     `* Re: Cost of handling misaligned access2Marcus
18 Feb 25  i      `- Re: Cost of handling misaligned access1BGB
17 Feb 25  `* Re: Cost of handling misaligned access5Terje Mathisen
17 Feb 25   +- Re: Cost of handling misaligned access1Thomas Koenig
17 Feb 25   `* Re: Cost of handling misaligned access3MitchAlsup1
17 Feb 25    `* Re: Cost of handling misaligned access2Terje Mathisen
17 Feb 25     `- Re: Cost of handling misaligned access1MitchAlsup1

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