[PATCH 0/2] alpha: enable building with clang

[Matt Turner <mattst88@gmail.com>]

Two small patches to let the alpha kernel build with clang.

The first registers the clang target triple and stops passing -Wa,-mev6
when the compiler is not gcc.  That flag exists to keep gas from emulating
instructions it believes the target lacks; it is a gas-only option and
clang's integrated assembler does not emulate instructions, so it is not
needed there.

The second fixes two uses of local register-asm variables that clang does
not honor.  clang treats `register unsigned long x __asm__("$N")` as the
named register only where the variable appears as an inline-asm operand,
so reading one to get the live $gp or $sp yields an undefined value.
trap_init() passed that to PAL_wrkgp and load_PCB() stored it into the
PCB for swpctx, either of which wedges an early boot.

Note that the alpha backend is not in upstream LLVM.  It lives in

  https://github.com/alphalinux-org/llvm-project

and is a work in progress, so the scripts/Makefile.clang entry has no
effect with an upstream clang today.  I am sending this now because the
second patch is a real bug in its own right -- the register-asm reads are
only guaranteed to work by gcc's implementation, not by anything either
compiler documents -- but I understand if the kbuild side would rather
wait for the backend to land upstream.

---
Matt Turner (2):
      alpha: enable building with clang
      alpha: read $gp and $sp explicitly for clang

 arch/alpha/Makefile       | 8 +++++++-
 arch/alpha/kernel/traps.c | 4 +++-
 arch/alpha/mm/init.c      | 3 +--
 scripts/Makefile.clang    | 1 +
 4 files changed, 12 insertions(+), 4 deletions(-)
---
base-commit: 0e6be1d34ae92e2b0dbc1b7410d422b22464389a
change-id: 20260803-alpha-clang-6acd144eb86c

Best regards,
-- 
Matt Turner <mattst88@gmail.com>