From: Ralf Baechle <ralf@oss.sgi.com>
To: ulfc@calypso.engr.sgi.com, ac131313@cygnus.com,
alan@linuxcare.com.au, binutils@sourceware.cygnus.com,
gdb-patches@sourceware.cygnus.com, geoffk@cygnus.com
Subject: Re: [rfc] For mips, sign-extended ecoff offsets
Date: Sun, 25 Jun 2000 14:13:00 -0000 [thread overview]
Message-ID: <20000625224009.A3529@bacchus.dhis.org> (raw)
In-Reply-To: <20000620034102.18244.qmail@daffy.airs.com>
On Mon, Jun 19, 2000 at 08:41:02PM -0700, Ian Lance Taylor wrote:
> > On a 64-bit MIPS processor 32-bit addresses are of course sign
> > extended, but this shouldn't concern the 32-bit BFD backend for MIPS
> > in any way. Whether we sign extend the addresses or not shouldn't
> > make any difference except in our internal representation of the
> > bfd_vma. I may be wrong though!
>
> The 64-bit MIPS machines often use the 32-bit ELF format, typically
> because they have 32-bit memory addresses (I forget whether trying to
> access 0x0000000087654321 gives you 0xffffffff87654321 or a trap).
>
> I think the real reason this happens is historical--because we didn't
> have a 64-bit MIPS format when we started supporting 64-bit MIPS
> chips. I don't think there is any particularly legitimate reason to
> use a 32-bit format for a 64-bit chip.
We do that for Linux/MIPS64. Originally I came up with this due to the
incredible brokeness of ld for 64-bit MIPS ELF. It allows us to generate
64-bit code that is more compact than standard 64-bit code because dla get
expanded to only 2 instructions like in 32-bit code. All it takes is
proper placement of the code into the 32-bit address space. We still
have kept the advantages of 64-bit code.
Ralf
next prev parent reply other threads:[~2000-06-25 14:13 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-06-19 5:14 Andrew Cagney
2000-06-19 8:48 ` Alan Modra
2000-06-19 18:18 ` Andrew Cagney
2000-06-19 18:47 ` Ulf Carlsson
2000-06-19 18:57 ` Alan Modra
2000-06-19 19:16 ` Andrew Cagney
2000-06-19 20:08 ` Geoff Keating
2000-06-19 20:41 ` Ian Lance Taylor
2000-06-25 14:13 ` Ralf Baechle [this message]
[not found] ` <14670.59816.517716.492387@calypso.engr.sgi.com>
2000-06-19 21:30 ` Geoff Keating
2000-06-19 18:50 ` Alan Modra
2000-06-19 19:23 ` Andrew Cagney
2000-06-19 20:39 ` Ian Lance Taylor
2000-06-23 0:28 ` Andrew Cagney
2000-06-23 9:48 ` Ian Lance Taylor
2000-07-03 23:47 ` Andrew Cagney
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