Date: Tue, 30 Nov 1999 09:35:34 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Ville-Pertti Keinonen <will@iki.fi> Cc: marcel@scc.nl, current@FreeBSD.ORG Subject: Re: kernel: -mpreferred-stack-boundary=2 ?? Message-ID: <199911301735.JAA25885@apollo.backplane.com> References: <19991130133337.25847.qmail@ns.demophon.com>
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:> > Anyhow, I'll repeat it here - stack alignment does *not* break
:> > link-compatibility. It does not change calling conventions, it just
:> > adds padding after the args to ensure that local variables can be
:> > predictably aligned.
:
:> So, how does aligning stackframes affect the inherently static property
:> of code size then?
:
:Instructions are inserted to perform that alignment (add padding).
:When the alignment is 2 (i.e. on 4-byte boundaries), no padding is
:required in typical cases.
I can't think of a single case where the stack isn't inherently
4-byte aligned already, whether you use the option or not.
To whomever added the option: Did you actually test to see that
this option resulted in an improvement? If not, I recommend removing
it. It sounds like unnecessary extra junk to me.
-Matt
Matthew Dillon
<dillon@backplane.com>
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