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From: "yann at droneaud dot fr" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/57908] alignment of arrays allocated stack on amd64/x86_64: 16 bytes ?
Date: Tue, 16 Jul 2013 15:11:00 -0000	[thread overview]
Message-ID: <bug-57908-4-OzYhU062Qz@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-57908-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57908

--- Comment #4 from Yann Droneaud <yann at droneaud dot fr> ---
(In reply to Andrew Pinski from comment #2)
> Your test program is not fully testing things correctly.
>      kind         name              address   size   alignment   required
> >   object |       u8_5 |     0x7fffefdd4810 |    3 |        16 |        1
> >   object |       u8_6 |     0x7fffefdd4800 |    2 |      2048 |        1
> >   object |       u8_7 |     0x7fffefdd47ff |    1 |         1 |        1
> 
> Shows why.  There are two variables right next to each other but the
> alignment recorded is 2048 but that was just accidental.  The alignment of
> u8_6 is 16 due to the next variable at 10.

Have you noticed that u8_7 is an array of 1 element only ?
Array of 1 element (bytes) only are not aligned on 16 bytes boundary.
Array of 2 bytes and greater get aligned on 16 bytes boundary.

Should I show another test case ?


  parent reply	other threads:[~2013-07-16 15:11 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-16 14:35 [Bug c/57908] New: " yann at droneaud dot fr
2013-07-16 14:39 ` [Bug c/57908] " yann at droneaud dot fr
2013-07-16 15:03 ` pinskia at gcc dot gnu.org
2013-07-16 15:06 ` [Bug target/57908] " pinskia at gcc dot gnu.org
2013-07-16 15:11 ` yann at droneaud dot fr [this message]
2013-07-16 15:18 ` yann at droneaud dot fr
2013-07-16 15:20 ` yann at droneaud dot fr
2013-07-16 15:28 ` pinskia at gcc dot gnu.org
2013-07-16 15:32 ` yann at droneaud dot fr
2013-07-16 15:36 ` pinskia at gcc dot gnu.org
2013-07-16 15:56 ` yann at droneaud dot fr

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