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Re: [PATCH] x86: Add .nop directive to assembler
On Mon, Feb 19, 2018 at 05:03:43PM -0800, H.J. Lu wrote:
> On Mon, Feb 19, 2018 at 4:05 PM, Alan Modra <amodra@gmail.com> wrote:
> > On Mon, Feb 19, 2018 at 03:24:17PM -0800, H.J. Lu wrote:
> >> On Mon, Feb 19, 2018 at 3:19 PM, Alan Modra <amodra@gmail.com> wrote:
> >> > On Mon, Feb 19, 2018 at 10:08:38PM +0000, Maciej W. Rozycki wrote:
> >> >> On Mon, 19 Feb 2018, Alan Modra wrote:
> >> >>
> >> >> > > .nop is similar to .skip, except that it fills with NOPs. Yes, it can be used
> >> >> > > wherever .skip can be used.
> >> >> >
> >> >> > Given https://sourceware.org/ml/binutils/2018-02/msg00322.html I'm
> >> >> > inclined to think the name of the directive should change.
> >> >> > .skipnops perhaps?
> >> >>
> >> >> Just `.nops' maybe? There doesn't appear to be any matching mnemonic in
> >> >> opcodes/.
> >> >
> >> > I'd be happy with that too.
> >>
> >> There is no guarantee that one of those NO_PSEUDO_DOT targets or the new
> >> NO_PSEUDO_DOT target won't have an instruction called nops or skipnops in
> >> the future.
> >
> > If a target adds an instruction like that, then the target will need
> > to deal with it. For example, as the spu target deals with "set" and
> > "equ" which existed as directives before the spu defined them as
> > instructions.
> >
> > In this case the use of "nop" as an instruction existed before you
> > decided to define ".nop" as a directive, and lack of testing resulted
> > in not discovering the NO_PSEUDO_DOT clash. I suspect we wouldn't be
> > having this conversation if you had run a full test suite regression,
> > rather than just testing x86. You yourself would have chosen
> > something other than ".nop" as a directive!
>
> I would have chosen .nop and handled it for NO_PSEUDO_DOT targets.
>
> Here is a patch to rename .nop to .nops. OK for master?
>
> --
> H.J.
> From eb81600ebb30f513732e395c524bcc9dca4de00a Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Mon, 19 Feb 2018 16:53:28 -0800
> Subject: [PATCH] Rename .nop directive to .nops
>
> Since directives of NO_PSEUDO_DOT targets don't have the leading '.'
> and "nop" can be a valid instruction, rename .nop directive to .nops
> to avoid conflict.
>
> * NEWS: Rename .nop to .nops.
> * doc/as.texinfo: Likewise.
> * read.c (potable): Add "nops". Remove "nop".
> (s_nop): Renamed to ...
> (s_nops): This.
> * read.h (s_nop): Renamed to ...
> (s_nops): This.
> * write.c (cvt_frag_to_fill): Rename .nop to .nops.
> (md_generate_nops): Likewise.
> (relax_segment): Likewise.
> * testsuite/gas/i386/nop-1.d: Updated.
> * testsuite/gas/i386/nop-1.s: Likewise.
> * testsuite/gas/i386/nop-2.d: Likewise.
> * testsuite/gas/i386/nop-2.s: Likewise.
> * testsuite/gas/i386/nop-3.d: Likewise.
> * testsuite/gas/i386/nop-3.s: Likewise.
> * testsuite/gas/i386/nop-4.d: Likewise.
> * testsuite/gas/i386/nop-4.s: Likewise.
> * testsuite/gas/i386/nop-5.d: Likewise.
> * testsuite/gas/i386/nop-5.s: Likewise.
> * testsuite/gas/i386/nop-6.d: Likewise.
> * testsuite/gas/i386/nop-6.s: Likewise.
> * testsuite/gas/i386/nop-bad-1.l: Likewise.
> * testsuite/gas/i386/nop-bad-1.s: Likewise.
> * testsuite/gas/i386/x86-64-nop-1.d: Likewise.
> * testsuite/gas/i386/x86-64-nop-2.d: Likewise.
> * testsuite/gas/i386/x86-64-nop-3.d: Likewise.
> * testsuite/gas/i386/x86-64-nop-4.d: Likewise.
> * testsuite/gas/i386/x86-64-nop-5.d: Likewise.
> * testsuite/gas/i386/x86-64-nop-6.d: Likewise.
OK. I think this is the best solution from a maintenance point of
view.
--
Alan Modra
Australia Development Lab, IBM