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

[Icenowy Zheng]

在 2025-12-02星期二的 07:15 +0100，Heinrich Schuchardt写道：
> 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.

Well at least SPL is run on the S7 cores, although the SBI should keep
the S7 core from being running main 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/
> > 
>