Re: [PATCH 7/7] RISC-V: add zbb support to string functions

["Christoph Müllner" <christoph.muellner@vrull.eu>]

On Fri, Nov 25, 2022 at 5:39 PM Conor Dooley <conor@kernel.org> wrote:
>
> On Fri, Nov 25, 2022 at 05:35:39PM +0100, Christoph Müllner wrote:
> > On Fri, Nov 25, 2022 at 4:28 PM Andrew Jones <ajones@ventanamicro.com> wrote:
>
> > > /*
> > >  * Each sub-list is sorted alphabetically.
> > >  */
> > > #define S_EXTENSIONS                                                    \
> > >         __RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),         \
> > >         __RISCV_ISA_EXT_DATA(sstc, RISCV_ISA_EXT_SSTC),                 \
> > >         __RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),           \
> > >         __RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
> > >
> > > #define Zi_EXTENSIONS                                                   \
> > >         __RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),             \
> > >         __RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
> > >
> > > #define Zb_EXTENSIONS                                                   \
> > >         __RISCV_ISA_EXT_DATA(zbb, RISCV_ISA_EXT_ZICBOM),                \
> > >
> > > static struct riscv_isa_ext_data isa_ext_arr[] = {
> > >         Zi_EXTENSIONS
> > >         Zb_EXTENSIONS
> > >         S_EXTENSIONS
> > >         __RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
> > > };
> >
> > It might be worth to look how Binutils are grouping them:
> >   https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=bfd/elfxx-riscv.c#l1261
> >
> > They also group extensions together but use the following groups:
> >
> > const struct riscv_supported_ext *riscv_all_supported_ext[] =
> > {
> >   riscv_supported_std_ext,
> >   riscv_supported_std_z_ext,
> >   riscv_supported_std_s_ext,
> >   riscv_supported_std_zxm_ext,
> >   riscv_supported_vendor_x_ext,
> >   NULL
> > };
>
> I think in this case, Drew's differentiation between Zi & Zb is an
> improvement :)


That might be the case, but it also brings up the following questions:
Where to put Zf* extensions (between Zi and Zb)?
Where to put Zk* and Zv* (after Zb*)?
Adding a subgroup for each Z{N}* extension might result in many small
groups with little benefit.

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