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Re: [PATCHv4] Add support for O32 FPXX ABI
- From: "Maciej W. Rozycki" <macro at codesourcery dot com>
- To: Richard Sandiford <rdsandiford at googlemail dot com>
- Cc: Matthew Fortune <Matthew dot Fortune at imgtec dot com>, "binutils at sourceware dot org" <binutils at sourceware dot org>, "Moore, Catherine" <Catherine_Moore at mentor dot com>, "Joseph Myers (joseph at codesourcery dot com)" <joseph at codesourcery dot com>
- Date: Mon, 28 Jul 2014 22:14:00 +0100
- Subject: Re: [PATCHv4] Add support for O32 FPXX ABI
- Authentication-results: sourceware.org; auth=none
- References: <6D39441BF12EF246A7ABCE6654B0235320EB4042 at LEMAIL01 dot le dot imgtec dot org> <87fvhnma8u dot fsf at talisman dot default> <6D39441BF12EF246A7ABCE6654B0235320EB4A44 at LEMAIL01 dot le dot imgtec dot org> <871tt5urqn dot fsf at googlemail dot com>
On Mon, 28 Jul 2014, Richard Sandiford wrote:
> > I would also like to get rid of all the ctc1/cfc1/cttc1/cftc1 instructions
> > that allow the use of floating point register names: $f0. The problem with
> > these is that they don't actually write floating point registers but they
> > will interact with the oddspreg logic as their operands have type
> > OP_REG_FP. Anything relying on ctc1 $0, $f[0-31] is probably expecting the
> > wrong thing to happen anyway. If that's OK I'll do a separate patch?
>
> It's always dangerous to change something long-standing like that, but
> I agree it's weird. OTOH "ctc1 $0, $31" could be seen as confusing too
> (it isn't GPR 31).
Nor even a general coprocessor register (though I'm used to numeric $n
standing in MIPS-speak for any kind of register). If confusion is to be
avoided I'd envisage adding $c[0-31] aliases with `c' standing for
"control", i.e.:
ctc1 $0, $c31
(in addition to any "cooked" aliases such as "c1_fir").
Maciej