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Date:      01 Dec 1999 15:05:25 +0200
From:      Ville-Pertti Keinonen <will@iki.fi>
To:        Bruce Evans <bde@zeta.org.au>
Cc:        current@freebsd.org, tejblum@arc.hq.cti.ru
Subject:   Re: kernel: -mpreferred-stack-boundary=2 ??
Message-ID:  <86d7squ7ze.fsf@not.demophon.com>
In-Reply-To: Bruce Evans's message of "1 Dec 1999 09:57:48 %2B0200"
References:  <Pine.BSF.4.10.9912011806370.16906-100000@alphplex.bde.org.newsgate.clinet.fi>

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Bruce Evans <bde@zeta.org.au> writes:

> If the caller has passed a double, then the stack alignment can be determined
> at compile time and the current subl-type adjustment can be used.

Doubles are not aligned when passed as parameters and passing a double
doesn't guarantee that there are local variables in the caller that
are doubles.

Anyhow, I don't think significant changes to gcc should be made in
FreeBSD when they only affect code size and performance, suggestions
to improve such things should be discussed on the gcc list and adopted
through official gcc releases.

The defaults can, of course, be changed, but userland code is not that
size-critical.  In any case, userland code should at least use
double-alignment, otherwise you could get poor performance in common
floating point code.  SSE code is not necessarily worth that much
consideration yet.


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