Huacai Chen 099cfcb98f LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg
commit 52c22661c79a7b6af7fad9f77200738fc6c51878 upstream.

When building kernel with LLVM there are occasionally such errors:

In file included from ./include/linux/spinlock.h:59:
In file included from ./include/linux/irqflags.h:17:
arch/loongarch/include/asm/irqflags.h:38:3: error: must not be $r0 or $r1
   38 |                 "csrxchg %[val], %[mask], %[reg]\n\t"
      |                 ^
<inline asm>:1:16: note: instantiated into assembly here
    1 |         csrxchg $a1, $ra, 0
      |                       ^

To prevent the compiler from allocating $r0 or $r1 for the "mask" of the
csrxchg instruction, the 'q' constraint must be used but Clang < 21 does
not support it. So force to use $t0 in the inline asm, in order to avoid
using $r0/$r1 while keeping the backward compatibility.

Cc: stable@vger.kernel.org
Link: https://github.com/llvm/llvm-project/pull/141037
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Suggested-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-06-27 11:08:58 +01:00
2025-06-27 11:08:57 +01:00
2022-09-28 09:02:20 +02:00
2025-06-19 15:28:47 +02:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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