[PATCH 2/2] RISC-V: Enable x0 base relaxation for relax_pc even if --no-relax-gp.

[Fangrui Song]

On Thu, Apr 27, 2023 at 11:29 PM Nelson Chu <nelson@rivosinc.com> wrote:
>
> Committed, thanks.
>
> Nelson

Thanks. I cannot find any information about "x0 base relaxation" on
the Internet.
It is worth a test: if I force `bfd_vma gp = 0;`, check-ld
RUNTESTFLAGS='ld-riscv-elf.exp' will still pass :)

> On Fri, Apr 21, 2023 at 4:28 PM Nelson Chu <nelson@rivosinc.com> wrote:
>
> > Let --no-relax-gp only disable the gp relaxation for lui and pcrel
> > relaxations, since x0 base and gp relaxations are different optimizations
> > in fact, but just use the same function to handle.
> >
> > bfd/
> >         * elfnn-riscv.c (_bfd_riscv_relax_pc): Like _bfd_riscv_relax_lui,
> >         set gp to zero when --no-relax-gp, then we should still keep the
> >         x0 base relaxation.
> >         (_bfd_riscv_relax_section): Enable _bfd_riscv_relax_pc when
> >         --no-relax-gp, we will disable the gp relaxation in the
> >         _bfd_riscv_relax_pc.
> > ---
> >  bfd/elfnn-riscv.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/bfd/elfnn-riscv.c b/bfd/elfnn-riscv.c
> > index 499f51ee857..77a732b6a08 100644
> > --- a/bfd/elfnn-riscv.c
> > +++ b/bfd/elfnn-riscv.c
> > @@ -4721,7 +4721,9 @@ _bfd_riscv_relax_pc (bfd *abfd ATTRIBUTE_UNUSED,
> >                      bool undefined_weak)
> >  {
> >    struct riscv_elf_link_hash_table *htab = riscv_elf_hash_table
> > (link_info);
> > -  bfd_vma gp = riscv_global_pointer_value (link_info);
> > +  bfd_vma gp = htab->params->relax_gp
> > +              ? riscv_global_pointer_value (link_info)
> > +              : 0;
> >
> >    BFD_ASSERT (rel->r_offset + 4 <= sec->size);
> >
> > @@ -4942,7 +4944,7 @@ _bfd_riscv_relax_section (bfd *abfd, asection *sec,
> >                    || type == R_RISCV_TPREL_LO12_I
> >                    || type == R_RISCV_TPREL_LO12_S)
> >             relax_func = _bfd_riscv_relax_tls_le;
> > -         else if (!bfd_link_pic (info) && htab->params->relax_gp
> > +         else if (!bfd_link_pic (info)
> >                    && (type == R_RISCV_PCREL_HI20
> >                        || type == R_RISCV_PCREL_LO12_I
> >                        || type == R_RISCV_PCREL_LO12_S))
> > --
> > 2.39.2 (Apple Git-143)
> >
> >