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Re: [PATCH] Fix distinction of 32/64bit addresses in MIPS gas
- To: cgd at broadcom dot com
- Subject: Re: [PATCH] Fix distinction of 32/64bit addresses in MIPS gas
- From: "H . J . Lu" <hjl at lucon dot org>
- Date: Thu, 6 Sep 2001 11:07:51 -0700
- Cc: ica2_ts at csv dot ica dot uni-stuttgart dot de, binutils at sources dot redhat dot com
- References: <20010831193107.A10362@rembrandt.csv.ica.uni-stuttgart.de> <firstname.lastname@example.org> <email@example.com> <20010831204556.C17249@rembrandt.csv.ica.uni-stuttgart.de> <firstname.lastname@example.org> <email@example.com> <20010831143107.A4532@lucon.org> <firstname.lastname@example.org> <20010906105014.A32456@lucon.org> <email@example.com>
On Thu, Sep 06, 2001 at 10:59:29AM -0700, firstname.lastname@example.org wrote:
> "H . J . Lu" <email@example.com> writes:
> > > > What is the 32bit address of `foo'?
> > >
> > > bit 31 may or may not be set, depending on what exactly you're
> > > compiling.
> > Let me get this. Correct me if I am wrong. It seems that you want
> > to use 64bit registers in an o32 binary. Am I right?
> Uh, the way you phrase that, i get the feeling that you think i'm
> silly for saying "yes." But I think that's probably only because you
I won't call it silly.
> structure the question unfavforably. I don't think I said anything
> about "an o32 binary," just a 32-bit ELF binary.
I just want to make sure we are on the same page.
> "mips64-elf" tools have, historically, generated:
> * 32-bit ELF
> * mips3-compatible code (including use of full 64-bit GPRs).
> Unless you say -mlong64, pointers and longs will be 32-bit, but you'll
> use full 64-bit GPRs for 'long long'.
> If you do say -mlong64, you'll get 64-bit pointers and longs, in your
> 64-bit GPRs.
> All with a 32-bit ELF format. (And, using R_MIPS_64 to represent
> pointers in the object files.)
> I don't really _know_ what ABI it uses. I had always thought of it as
> "o64", which in my mind was "o32 naively extended for 64-bit GPRs,"
> but really i don't know that that's correct. In fact, I don't really
> _care_ what ABI it uses. We understand the calling conventions well
> enough for embedded development use, which is where we're using it.
I think that is ok as long as R_MIPS_64 is not used for o32 binaries.
Maybe it is time to give a new BFD target for mips64-elf since it does
represent a different ABI which includes R_MIPS_64. R_MIPS_64 should be
forbidden for o32 binaries.