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Date: Fri, 10 Aug 2018 09:21:32 -0300
From: Eduardo Habkost <ehabkost@redhat.com>
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Subject: Re: [Qemu-devel] [RFC PATCH 1/4] scripts/decodetree.py: add a
 disassembly generator (HACK!)
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To: Alex =?iso-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>
Cc: qemu-devel@nongnu.org, qemu-arm@nongnu.org, richard.henderson@linaro.org, Cleber Rosa <crosa@redhat.com>

On Fri, Aug 10, 2018 at 09:55:50AM +0100, Alex Benn=E9e wrote:
>=20
> Eduardo Habkost <ehabkost@redhat.com> writes:
>=20
> > On Wed, Aug 08, 2018 at 01:39:31PM +0100, Alex Benn=E9e wrote:
> >> Given our issues with failing disassembly we could try and re-use th=
e
> >> decode tree data to output what instruction is being decoded. This
> >> will be used if registered as a fall-back for when the "proper"
> >> disassembler fails to decode an instruction.
> >>
> >> Signed-off-by: Alex Benn=E9e <alex.bennee@linaro.org>
> >
> > I don't have an opinion on the approach you are taking, but the
> > Python code you are adding is consistent with the existing style
> > of the script.
> >
> > That said, I find the existing code full of output() calls very
> > hard to read.  If anybody wants to volunteer to improve the
> > readability of the output generation, it would be welcome.
>=20
> If we expect to have the script output a number of different forms I
> guess re-factoring it with some sort of template based approach would b=
e
> worthwhile. I wonder if there are other examples in the code base? We
> wouldn't want to have multiple template types.

QAPI scripts also generates C code, and I find them more
readable[1].

I think a true template language would be even better than QAPI's
approach, but I don't see an obvious candidate that would be
worth adding another build dependency to QEMU.


[1] Compare:

def output_decl(self):
    global translate_scope
    global translate_prefix
    output('typedef ', self.base.base.struct_name(),
           ' arg_', self.name, ';\n')
    output(translate_scope, 'bool ', translate_prefix, '_', self.name,
           '(DisasContext *ctx, arg_', self.name,
           ' *a, ', insntype, ' insn);\n')

And:

def gen_visit_members_decl(name):
    return mcgen('''

void visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **e=
rrp);
''',
                 c_name=3Dc_name(name))

--=20
Eduardo