From: Geoff Keating <geoffk@cygnus.com>
To: ulfc@calypso.engr.sgi.com
Cc: binutils@sourceware.cygnus.com
Subject: Re: [rfc] For mips, sign-extended ecoff offsets
Date: Mon, 19 Jun 2000 21:30:00 -0000 [thread overview]
Message-ID: <200006200430.VAA10600@localhost.cygnus.com> (raw)
In-Reply-To: <14670.59816.517716.492387@calypso.engr.sgi.com>
> From: Ulf Carlsson <ulfc@calypso.engr.sgi.com>
> Date: Mon, 19 Jun 2000 20:48:56 -0700 (PDT)
>
> > > 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).
>
> We always have 0x87654321 in the 32-bit ELF file. It probably doesn't
> matter what our internal representation is since we'll drop the upper
> 32 bits when we write the ELF file in either case and the address will
> be properly sign extended again when the ELF file is loaded.
A similar argument was used originally to justify not forcing BFD to
do the right thing.
An example where it does matter is when you try to work out whether
a 32-bit pc-relative operand can hold the offset from 0x10000000 to
0xA0000000, or whether there should be overflow.
In GDB, it matters whenever you are comparing a value in a register to
an address in the object file.
--
- Geoffrey Keating <geoffk@cygnus.com>
next prev parent reply other threads:[~2000-06-19 21:30 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
[not found] ` <14670.59816.517716.492387@calypso.engr.sgi.com>
2000-06-19 21:30 ` Geoff Keating [this message]
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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