From: Greg McGary <gkm@eng.ascend.com>
To: egcs@cygnus.com
Cc: law@cygnus.com
Subject: STRICT_ALIGNMENT is too strict for m68k
Date: Thu, 14 May 1998 15:38:00 -0000 [thread overview]
Message-ID: <199805142238.PAA00298@tucson-net-82.eng.ascend.com> (raw)
m68k.h has STRICT_ALIGNMENT unconditionally defined as 1, although a
few host-specific includes (linux.h. ccur-GAS.h, plexus.h) override it
as 0. My experience is only with the 68302 (68000 core) and 68360
(a.k.a. cpu32, mostly 68020 core), so I can't make generalizations,
but I know that the 68020 cores (and probably later) do not require
strict alignment, whereas the 68000 (and 68010?) do require it. The
fact that STRICT_ALIGNMENT is on unconditionally causes gcc to
generate byte-at-a-time memory access for packed structures which is
very inefficient in both time & space.
It would be a very nice improvement if STRICT_ALIGNMENT were made to
be conditional on the CPU implementation.
Would people with broader knowledge of the m68k line please tell me
which CPU cores allow unaligned word access?
next reply other threads:[~1998-05-14 15:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-05-14 15:38 Greg McGary [this message]
1998-05-14 22:14 ` Rask Ingemann Lambertsen
1998-05-15 12:05 ` Jim Wilson
1998-05-15 14:35 ` Greg McGary
1998-05-16 19:47 ` Richard Henderson
1998-05-18 12:09 ` Jim Wilson
1998-05-19 8:03 ` Kamil Iskra
1998-05-19 20:24 ` Jim Wilson
1998-05-18 11:32 ` Jim Wilson
1998-05-18 23:58 ` Jeffrey A Law
1998-05-16 19:47 ` Kamil Iskra
1998-05-16 22:35 ` Richard Henderson
1998-05-17 10:51 ` Kamil Iskra
1998-05-17 18:05 ` Jeffrey A Law
1998-05-18 6:02 ` Andreas Schwab
1998-05-18 23:58 ` Jim Wilson
1998-05-20 2:27 ` Andreas Schwab
1998-05-19 21:17 ` Rask Ingemann Lambertsen
1998-05-18 12:09 ` Jim Wilson
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