From: Jeffrey A Law <law@cygnus.com>
To: Dave Love <d.love@dl.ac.uk>
Cc: egcs@cygnus.com
Subject: Re: x86 stack alignment redux
Date: Thu, 11 Dec 1997 23:10:00 -0000 [thread overview]
Message-ID: <16883.881910032@hurl.cygnus.com> (raw)
In-Reply-To: <rzq3el01z6k.fsf@djlvig.dl.ac.uk>
In message <rzq3el01z6k.fsf@djlvig.dl.ac.uk>you write:
> With this change, a glibc2-based system such as is now apparently
> becoming usable, and -malign-double, g77 users running on GNUish
> 686-based boxes should no longer suffer an average 50% perfromance hit
> because doubles on the stack only get word-aligned (or a smaller hit
> on 586). Previous discussion suggested it's a bug if STACK_BOUNDARY
> doesn't agree with the initial stack pointer alignment and glibc2
> ensures initial double alignment.
>
> This really is important to serious scientific users with high-profile
> projects of the sort I understand have just been slagging off g77/gcc
> at a high-performance computing meeting here.
>
> 1997-11-13 Dave Love <d.love@dl.ac.uk>
>
> * config/i386/linux.h (STACK_BOUNDARY): Define as 64 for glibc2.
> * config/i386/gnu.h (STACK_BOUNDARY): Define as 64.
I installed this.
However, I'm a little worried about things breaking if we happen to mix
code compiled with an old compiler (say egcs-1.0 or gcc-2.7) with code
which assumes a 64bit stack boundary. Isn't this change going to break
that case, or does the prologue/epilogue code for older compilers always
allocate 64bit hunks?
jeff
next prev parent reply other threads:[~1997-12-11 23:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-11-13 9:28 Dave Love
1997-12-11 23:10 ` Jeffrey A Law [this message]
1997-12-11 23:40 ` H.J. Lu
1997-12-12 0:18 ` Jeffrey A Law
1997-12-12 7:28 ` H.J. Lu
1997-12-12 10:18 ` Marc Lehmann
1997-12-12 13:04 ` Dave Love
1997-12-14 22:36 ` Jeffrey A Law
1997-12-12 13:04 ` Marc Lehmann
1997-12-14 22:41 ` Jeffrey A Law
1997-12-12 13:04 Mike Stump
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