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Re: [PATCH 02/12] x86: fold various AVX512VL templates into their AVX512F counterparts
>>> On 04.06.18 at 14:41, <hjl.tools@gmail.com> wrote:
> what is the advantage of
>
> +static const initializer opcode_modifier_shorthands[] =
> +{
> + { "Disp8ShiftVL", "Disp8MemShift=" stringify(DISP8_SHIFT_VL) },
> +};
> +
>
> How much does it save? I can't tell what an entry has by just
> looking at i386-opc.h.
This isn't about space saving at all. It's about not introducing yet
another easy to break case of specifying some arbitrary number in
various i386-opc.tbl entries. Writing Disp8MemShift=7 there is simply
unreadable and unmaintainable (as is for example Evex=2 to mean
EVEX128 or, even worse, VexW=1 to mean VEX.W=0 and VexW=2
to mean VEX.W=1). Long term I'm intending to replace all of these
by suitable (and readable!) shorthands.
With the approach above, anyone can change the definition of
DISP8_SHIFT_VL to another suitable number without having to
touch any other place (and in particular without having to modify
dozens or even hundreds of templates).
If you dislike the shorthand approach, passing i386-opc.tbl through
the C pre-processor would be another option.
Jan