[PATCH 3/N] Come up with casm global state.

Richard Biener richard.guenther@gmail.com
Tue Nov 9 12:49:23 GMT 2021


On Fri, Nov 5, 2021 at 3:27 PM Martin Liška <mliska@suse.cz> wrote:
>
> On 10/26/21 09:45, Richard Biener wrote:
> > On Mon, Oct 25, 2021 at 6:32 PM Segher Boessenkool
> > <segher@kernel.crashing.org> wrote:
> >>
> >> Hi!
> >>
> >> On Mon, Oct 25, 2021 at 03:36:25PM +0200, Martin Liška wrote:
> >>> --- a/gcc/config/rs6000/rs6000-internal.h
> >>> +++ b/gcc/config/rs6000/rs6000-internal.h
> >>> @@ -189,4 +189,13 @@ extern bool rs6000_passes_vector;
> >>>   extern bool rs6000_returns_struct;
> >>>   extern bool cpu_builtin_p;
> >>>
> >>> +struct rs6000_asm_out_state : public asm_out_state
> >>> +{
> >>> +  /* Initialize ELF sections. */
> >>> +  void init_elf_sections ();
> >>> +
> >>> +  /* Initialize XCOFF sections. */
> >>> +  void init_xcoff_sections ();
> >>> +};
> >>
> >> Our coding convention says to use "class", not "struct" (since this
> >> isn't valid C code at all).
> >>
> >>> -  sdata2_section
> >>> + sec.sdata2
> >>>       = get_unnamed_section (SECTION_WRITE, output_section_asm_op,
> >>>                           SDATA2_SECTION_ASM_OP);
> >>
> >> (broken indentation)
> >>
> >>> +/* Implement TARGET_ASM_INIT_SECTIONS.  */
> >>
> >> That comment is out-of-date.
> >>
> >>> +static asm_out_state *
> >>> +rs6000_elf_asm_init_sections (void)
> >>> +{
> >>> +  rs6000_asm_out_state *target_state
> >>> +    = new (ggc_alloc<rs6000_asm_out_state> ()) rs6000_asm_out_state ();
> >>
> >> Hrm, maybe we can have a macro or function that does this, ggc_new or
> >> something?
> >>
> >>> +/* Implement TARGET_ASM_INIT_SECTIONS.  */
> >>> +
> >>> +static asm_out_state *
> >>> +rs6000_xcoff_asm_init_sections (void)
> >>
> >> Here, too.  Both implementations are each one of several functions that
> >> together implement the target macro.
> >>
> >>> +    /* The section that holds the DWARF2 frame unwind information, when known.
> >>> +       The section is set either by the target's init_sections hook or by the
> >>> +       first call to switch_to_eh_frame_section.  */
> >>> +    section *eh_frame;
> >>> +
> >>> +    /* RS6000 sections.  */
> >>
> >> Nothing here?  Just remove the comment header?
> >>
> >> The idea looks fine to me.
> >
> > Yeah, of course then the target hook does not need to do the allocation
> > and we could simply keep the current init_sections hook but change it
> > to take the asm_out_state to initialize as argument.
>
> Makes sense.
>
> >
> > Note that I'd put
> >
> > +    /* RS6000 sections.  */
> > +
> > +    /* ELF sections.  */
> > +    section *toc;
> > +    section *sdata2;
> > +
> > +    /* XCOFF sections.  */
> > +    section *read_only_data;
> > +    section *private_data;
> > +    section *tls_data;
> > +    section *tls_private_data;
> > +    section *read_only_private_data;
> >
> > into a union, thus
> >
> >     union {
> >         struct /* RS6000 sections */ {
> >             /* ELF sections.  */
> >            section *toc;
> > ...
> >         } rs6000;
> >         struct /* darwin sections */ {
> >   ...
> >     };
>
> Union is a bit tricky for GGC marking script, but we can manage that.
>
> >
> > not sure whether we need some magic GTY marking here to make
> > it pick up the 'correct' set.  Another alternative would be
> >
> >           section *target[MAX_TARGET_SECTIONS];
> >
> > and #defines in the targets mapping the former global variables to
> > indices in that array.
> >
> > All of this isn't "nice C++" of course, but well ... I'm not the one
> > to insist ;)
>
> Anyway, I took a look at targets that do call the init_sections hook and I noticed
> Darwin uses pretty many sections and comes up with an array that is defined here:
> ./gcc/config/darwin-sections.def
>
> I tend to creating all sections in asm_out_state with DEF_SECTION, where the list
> will be extensible with a target-specific definition list.
>
> What do you think Richi?

That sounds good to me as well.

Richard.

>
> Thanks,
> Martin
>
> >
> > Richard.
> >
> >>
> >> Segher
>


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