[PATCH] RISC-V: Add an implicit dependency for Zawrs

[Andrew Waterman]

But that's not what the normative text in the spec says!  Using
non-normative notes to infer dependencies between extensions is
dangerous territory.

It is true that the WRS instructions aren't useful without the LR
instruction, but it is also true that Binutils shouldn't be inventing
extension dependencies that aren't normatively justified.


On Mon, Oct 7, 2024 at 11:07 PM Xiao Zeng <zengxiao@eswincomputing.com> wrote:
>
> There is a description in <https://github.com/riscv/riscv-isa-manual/blob/main/src/zawrs.adoc>:
>
> "The instructions in the Zawrs extension are only useful in conjunction
> with the LR instruction, which is provided by the Zalrsc component
> of the A extension."
>
> It can be concluded that: zawrs -> zalrsc.
>
> The implementation in gcc is as follows:
> <https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=c01e3aaae79ecd439ad35063db3dee9775f3aefa>
>
> bfd/ChangeLog:
>
>         * elfxx-riscv.c: zawrs -> zalrsc.
>
> gas/ChangeLog:
>
>         * testsuite/gas/riscv/imply.d: Add implicit dependency
>         testing for zawrs.
>         * testsuite/gas/riscv/imply.s: Updated.
>
> Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>
> ---
>  bfd/elfxx-riscv.c               | 1 +
>  gas/testsuite/gas/riscv/imply.d | 1 +
>  gas/testsuite/gas/riscv/imply.s | 1 +
>  3 files changed, 3 insertions(+)
>
> diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
> index 4b48d8ee9f0..b7b4d95195e 100644
> --- a/bfd/elfxx-riscv.c
> +++ b/bfd/elfxx-riscv.c
> @@ -1184,6 +1184,7 @@ static struct riscv_implicit_subset riscv_implicit_subsets[] =
>
>    {"zabha", "+zaamo", check_implicit_always},
>    {"zacas", "+zaamo", check_implicit_always},
> +  {"zawrs", "+zalrsc", check_implicit_always},
>    {"a", "+zaamo,+zalrsc", check_implicit_always},
>
>    {"xsfvcp", "+zve32x", check_implicit_always},
> diff --git a/gas/testsuite/gas/riscv/imply.d b/gas/testsuite/gas/riscv/imply.d
> index 26eff8c650a..64dda77a9f8 100644
> --- a/gas/testsuite/gas/riscv/imply.d
> +++ b/gas/testsuite/gas/riscv/imply.d
> @@ -17,6 +17,7 @@ SYMBOL TABLE:
>  [0-9a-f]+ l       .text        0+000 \$xrv32i2p1_m2p0_zmmul1p0
>  [0-9a-f]+ l       .text        0+000 \$xrv32i2p1_zaamo1p0_zabha1p0
>  [0-9a-f]+ l       .text        0+000 \$xrv32i2p1_zaamo1p0_zacas1p0
> +[0-9a-f]+ l       .text        0+000 \$xrv32i2p1_zalrsc1p0_zawrs1p0
>  [0-9a-f]+ l       .text        0+000 \$xrv32i2p1_a2p1_zaamo1p0_zalrsc1p0
>  [0-9a-f]+ l       .text        0+000 \$xrv32i2p1_zicsr2p0_zve32x1p0_zvl32b1p0_xsfvcp1p0
>  [0-9a-f]+ l       .text        0+000 \$xrv32i2p1_f2p2_d2p2_v1p0_zicsr2p0_zve32f1p0_zve32x1p0_zve64d1p0_zve64f1p0_zve64x1p0_zvl128b1p0_zvl32b1p0_zvl64b1p0
> diff --git a/gas/testsuite/gas/riscv/imply.s b/gas/testsuite/gas/riscv/imply.s
> index dabb08d8c8b..c831ea63f04 100644
> --- a/gas/testsuite/gas/riscv/imply.s
> +++ b/gas/testsuite/gas/riscv/imply.s
> @@ -18,6 +18,7 @@ imply m
>
>  imply zabha
>  imply zacas
> +imply zawrs
>  imply a
>
>  imply xsfvcp
> --
> 2.17.1
>