[PATCH 1/2] RISC-V: implement private GCC library

[Heinrich Schuchardt]

On 12/2/25 06:28, Icenowy Zheng wrote:
> 在 2025-12-02星期二的 03:57 +0000，Yao Zi写道：
>> On Mon, Dec 01, 2025 at 06:49:03PM +0100, Heinrich Schuchardt wrote:
>>> The following functions are provided:
>>>
>>> Count leading zero bits
>>>
>>> * int __clzsi2 (unsigned int a)
>>> * int __clzdi2 (unsigned long a)
>>> * int __clzti2 (unsigned long long a)
>>>
>>> Count trailing zero bits
>>>
>>> * int __ctzsi2 (unsigned int a)
>>> * int __ctzdi2 (unsigned long a)
>>> * int __ctzti2 (unsigned long long a)
>>>
>>> Signed-off-by: Heinrich Schuchardt
>>> <heinrich.schuchardt at canonical.com>
>>> ---
>>
>> I noted there's another series with the same subject[1] sent almost
>> at
>> the same time, and I couldn't tell the difference at the first
>> glance.
>> Is this an incident?
>>
>>>   arch/Kconfig            |   1 +
>>>   arch/riscv/lib/Makefile |   2 +
>>>   arch/riscv/lib/clz.c    | 105
>>> ++++++++++++++++++++++++++++++++++++++++
>>>   arch/riscv/lib/ctz.c    |  95 ++++++++++++++++++++++++++++++++++++
>>>   lib/Kconfig             |   2 +-
>>>   5 files changed, 204 insertions(+), 1 deletion(-)
>>>   create mode 100644 arch/riscv/lib/clz.c
>>>   create mode 100644 arch/riscv/lib/ctz.c
>>>
>>> diff --git a/arch/Kconfig b/arch/Kconfig
>>> index 3133f892f94..4af0da2485f 100644
>>> --- a/arch/Kconfig
>>> +++ b/arch/Kconfig
>>> @@ -159,6 +159,7 @@ config PPC
>>>   config RISCV
>>>          bool "RISC-V architecture"
>>>          select CREATE_ARCH_SYMLINK
>>> +       select HAVE_PRIVATE_LIBGCC if 64BIT
>>
>> Are 32-bit platforms excluded for lacking of enough library
>> functions?

Yes. See 
https://lore.kernel.org/u-boot/20251201174904.652954-1-heinrich.schuchardt@canonical.com/T/#mbf44c9f5073649bbf2e1368ffbeaec82680a268d

>> Should we exclude !RISCV_ISA_F || !RISCV_ISA_D platforms as well?
>> Though

libgcc.a as provided by distros assumes that you have the D and F 
extensions. Either a specific libgcc.a will be needed or we will have to 
implement the missing functions in the private lib if such platforms.

It would make more sense to set CONFIG_USE_PRIVATE_LIBGCC=n for such 
platforms than setting CONFIG_HAVE_PRIVATE_LIBGCC=n.

Which way we want to go can be decided when such platforms arrive.

>> there's no in-tree 64-bit port without F/D extension.
> 
> The S7 core in U74-MC complex seems to have only IMAC, no F/D.
The S7 core is not supported by U-Boot.

Best regards

Heinrich

> 
>>
>>>          select HAVE_SETJMP
>>>          select HAVE_INITJMP
>>>          select SUPPORT_ACPI
>>
>> Regards,
>> Yao Zi
>>
>> [1]:
>> https://lore.kernel.org/u-boot/20251201174705.652626-1-zfsdt@canonical.com/
>