[PATCH] RISC-V: Checking 'm' extension when using RVV.

[Jiawei]

在 2025/1/22 9:18, Christoph Müllner 写道:
> On Wed, Jan 22, 2025 at 2:11 AM Jiawei <jiawei@iscas.ac.cn> wrote:
>>
>> 在 2025/1/21 23:55, Christoph Müllner 写道:
>>> On Tue, Jan 21, 2025 at 4:23 PM Jiawei <jiawei@iscas.ac.cn> wrote:
>>>> This patch add a new extension check when using `v` extension, it
>>>> currently should also enable `m` extension to make sure vector length
>>>> caculate correct.
>>> How to trigger this incorrect calculation?
>>> Is there an example?
>> I found this commit in gcc refer to this, please check it:
>>
>> https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=e589ffb6d78881572ddea21df0d9b6c2641d574d;hp=4cbbce045681c234387d8d56376ea179dc869229
> This means that GCC's RISC-V vectorizer backend depends on M.
> However, the V extension does not.
> And it is possible to write valid assembly files that include V
> instructions but no M instructions.
>
> So, if GCC needs M, then it is reasonable that GCC requests M to be enabled.
> However, this is independent of Binutils.
Thank you for your explanation, it corrected my misunderstanding.
>>
>> BR,
>>
>> Jiawei
>>
>>>> bfd/ChangeLog:
>>>>
>>>>           * elfxx-riscv.c (riscv_parse_check_conflicts): New check.
>>>>
>>>> gas/ChangeLog:
>>>>
>>>>           * testsuite/gas/riscv/march-fail-rv64i_v.d: New test.
>>>>           * testsuite/gas/riscv/march-fail-rv64i_v.l: New test.
>>>>
>>>> ---
>>>>    bfd/elfxx-riscv.c                            | 10 +++++++++-
>>>>    gas/testsuite/gas/riscv/march-fail-rv64i_v.d |  4 ++++
>>>>    gas/testsuite/gas/riscv/march-fail-rv64i_v.l |  3 +++
>>>>    3 files changed, 16 insertions(+), 1 deletion(-)
>>>>    create mode 100644 gas/testsuite/gas/riscv/march-fail-rv64i_v.d
>>>>    create mode 100644 gas/testsuite/gas/riscv/march-fail-rv64i_v.l
>>>>
>>>> diff --git a/bfd/elfxx-riscv.c b/bfd/elfxx-riscv.c
>>>> index c9e4b03b17d..150838d3d24 100644
>>>> --- a/bfd/elfxx-riscv.c
>>>> +++ b/bfd/elfxx-riscv.c
>>>> @@ -2123,7 +2123,15 @@ riscv_parse_check_conflicts (riscv_parse_subset_t *rps)
>>>>           (_("`xtheadvector' is conflict with the `v' extension"));
>>>>          no_conflict = false;
>>>>        }
>>>> -
>>>> +  /* We might use a multiplication to calculate the scalable vector length at
>>>> +     runtime.  Therefore, require the M extension.  */
>>>> +  if (riscv_lookup_subset (rps->subset_list, "v", &subset)
>>>> +      && !riscv_lookup_subset (rps->subset_list, "m", &subset))
>>>> +    {
>>>> +      rps->error_handler
>>>> +       (_("Currently the 'v' implementation requires the 'm' extension"));
>>>> +      no_conflict = false;
>>>> +    }
>>>>      bool support_zve = false;
>>>>      bool support_zvl = false;
>>>>      riscv_subset_t *s = rps->subset_list->head;
>>>> diff --git a/gas/testsuite/gas/riscv/march-fail-rv64i_v.d b/gas/testsuite/gas/riscv/march-fail-rv64i_v.d
>>>> new file mode 100644
>>>> index 00000000000..4d14bb4f9a9
>>>> --- /dev/null
>>>> +++ b/gas/testsuite/gas/riscv/march-fail-rv64i_v.d
>>>> @@ -0,0 +1,4 @@
>>>> +#as: -march=rv64i_v
>>>> +#source: empty.s
>>>> +#error_output: march-fail-rv64i_v.l
>>>> +
>>>> diff --git a/gas/testsuite/gas/riscv/march-fail-rv64i_v.l b/gas/testsuite/gas/riscv/march-fail-rv64i_v.l
>>>> new file mode 100644
>>>> index 00000000000..5386a942ec5
>>>> --- /dev/null
>>>> +++ b/gas/testsuite/gas/riscv/march-fail-rv64i_v.l
>>>> @@ -0,0 +1,3 @@
>>>> +Assembler messages:
>>>> +Error: Currently the 'v' implementation requires the 'm' extension
>>>> +
>>>> --
>>>> 2.43.0
>>>>