From owner-freebsd-arch@FreeBSD.ORG  Fri Dec 23 23:56:42 2011
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Date: Fri, 23 Dec 2011 23:56:42 +0000
From: Alexander Best <arundel@freebsd.org>
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Cc: freebsd-arch@freebsd.org
Subject: [rfc] removing -mpreferred-stack-boundary=2 flag for i386?
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hi there,

is -mpreferred-stack-boundary=2 really necessary for i386 builds any longer?
i built GENERIC (including modules) with and without that flag. the results
are:

1654496	bytes with the flag set
vs.
1654952	bytes with the flag unset

the gcc(1) man page states the following:

"
This extra alignment does consume extra stack space, and generally
increases code size.  Code that is sensitive to stack space usage,
such as embedded systems and operating system kernels, may want to
reduce the preferred alignment to -mpreferred-stack-boundary=2.
"

the comment in sys/conf/kern.mk however sorta suggests that the default
alignment of 4 bytes might improve performance.

cheers.
alex