[PATCH 1/2] RISC-V: Stop generating mapping symbol $x, replace with $x<isa>.

[Nelson Chu]

On Fri, Feb 21, 2025 at 4:27 PM Jan Beulich <jbeulich@suse.com> wrote:

> On 21.02.2025 07:33, Nelson Chu wrote:
> > --- a/gas/config/tc-riscv.c
> > +++ b/gas/config/tc-riscv.c
> > @@ -539,7 +539,12 @@ make_mapping_symbol (enum riscv_seg_mstate state,
> >         name = buff;
> >       }
> >        else
> > -     name = "$x";
> > +     {
> > +       /* The $x without isa shouldn't be generated since it will put
> more
> > +          burden on the linker when linking objects with different
> isa.  */
> > +       name = "$x";
> > +       as_warn (_("The mapping symbol $x shouldn't be generated"));
> > +     }
>
> What's the user to do about this, if it appears? Isn't this an internal

error?


> Also, nit: diagnostics normally don't start with a capital letter.
>

Git it, thanks.


>
> > @@ -585,11 +590,20 @@ make_mapping_symbol (enum riscv_seg_mstate state,
> >
> >    if (odd_data_padding)
> >      {
> > -      /* If the removed mapping symbol is $x+arch, then add it back to
> > -      the next $x.  */
> > -      const char *str = removed != NULL
> > -                     && strncmp (S_GET_NAME (removed), "$xrv", 4) == 0
> > -                     ? S_GET_NAME (removed) + 2 : NULL;
> > +      /* Search and find the previous $x+isa which in the same frag.  */
> > +      const char *str = NULL;
> > +      symbolS *p = symbol_previous (symbol);
> > +      for (; p != NULL; p = symbol_previous (p))
> > +     {
> > +       if (symbol_get_frag (p) == frag
> > +           && S_GET_NAME (p)
> > +           && strncmp (S_GET_NAME (p), "$xrv", 4) == 0
> > +           && S_GET_VALUE (p) <= S_GET_VALUE (symbol))
> > +         {
> > +           str = S_GET_NAME (p) + 2;
> > +           break;
> > +         }
> > +     }
> >        make_mapping_symbol (MAP_INSN, frag->fr_fix + 1, frag, str,
> >                          false/* odd_data_padding */);
>
> Are there any guarantees that str will not end up as NULL here? I.e. that
> such a "previous $x+isa" will be found?


In theory, there must be since we always added $x+isa at the beginning of
each section.  The odd paddings are handled in the riscv_handle_align at
the end, which all other normal mapping symbols should already be added,
including all $x+isa at the beginning of each section.  But that's in
theory, even though I never got the above as_warn messages for now after
building the multi-lib toolchains with newlib/glibc, and also passing the
gcc/binutils regressions.  So I use as_warn rather as_bad, since it should
just be a display issue for now, maybe just a warning without stopping
building or compiling it.  But yeah it's eventually an internal error, so
as_bad may be more suitable.

Thanks
Nelson
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