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Re: alignment
- To: "Andrew Morton" <andrewm at uow dot edu dot au>, <gcc at gcc dot gnu dot org>
- Subject: Re: alignment
- From: "Tim Prince" <tprince at computer dot org>
- Date: Sat, 15 Jul 2000 06:45:41 -0700
- References: <39705E5F.CE00658@uow.edu.au>
Did you do any performance studies? Did you enable the use of .p2align,
and did that change the situation? On the code I have worked with, I
saw no reason for using __volatile__ other than to hide bugs, and that
may make a difference.
Tim Prince
----- Original Message -----
From: "Andrew Morton" <andrewm@uow.edu.au>
To: <gcc@gcc.gnu.org>
Sent: Saturday, July 15, 2000 5:51 AM
Subject: alignment
> On x86, both gcc 2.7.2.3 and "2.96 19991116" are inserting `.align 4'
> ops after `jmp' instructions and also prior to `__asm__ __volatile__'.
>
> This causes a ~5% code size increase in the one Linux kernel file I
> looked at.
>
> Why does the compiler do this, and what would be the downside of
turning
> it off?
>
> Thanks.