x86/kbuild/64: Restrict clang versions that can use '-march=native'

There are two issues that can appear when building with clang and
'-march=native'.

The first issue is a compiler crash in the ipv6 stack with clang-18,
such as when building allmodconfig. This was frequently reported on the
LLVM issue tracker:

Link: https://github.com/llvm/llvm-project/issues?q=is%3Aissue%20ip6_rcv_core
  Stack dump:
  0.      Program arguments: clang ... -march=native ... net/ipv6/ip6_input.c
  1.      <eof> parser at end of file
  2.      Code generation
  3.      Running pass 'Function Pass Manager' on module 'net/ipv6/ip6_input.c'.
  4.      Running pass 'X86 DAG->DAG Instruction Selection' on function '@ip6_rcv_core'

The second issue is certain -Wframe-larger-than warnings that appear
with clang versions prior to 19, which introduced an optimization that
produces much better code:

Link: https://github.com/llvm/llvm-project/commit/90ba33099cbb17e7c159e9ebc5a512037db99d6d
  clang-18:

    drivers/media/pci/saa7164/saa7164-core.c:605:20: error: stack frame size (2392) exceeds limit (2048) in 'saa7164_irq' [-Werror,-Wframe-larger-than]
      605 | static irqreturn_t saa7164_irq(int irq, void *dev_id)
          |                    ^

  clang-19:

    drivers/media/pci/saa7164/saa7164-core.c:605:20: error: stack frame size (216) exceeds limit (128) in 'saa7164_irq' [-Werror,-Wframe-larger-than]
      605 | static irqreturn_t saa7164_irq(int irq, void *dev_id)
          |                    ^

Restrict the testing of the availability of '-march=native' to all
supported GCC versions and clang-19 and newer to avoid these known
resolved issues.

Fixes: 0480bc7e65dc ("x86/kbuild/64: Add the CONFIG_X86_NATIVE_CPU option to locally optimize the kernel with '-march=native'")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Tor Vic <torvic9@mailbox.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250324-x86-march-native-clang-19-and-newer-v1-1-3a05ed32a89e@kernel.org

diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 87bede96e8009ef3380613748f1b1f65eec3fef9..f928cf6e32524e32f10f9d4f35f82ab5c4fb0421 100644 (file)
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -248,6 +248,12 @@ endchoice
 config CC_HAS_MARCH_NATIVE
        # This flag might not be available in cross-compilers:
        def_bool $(cc-option, -march=native)
+       # LLVM 18 has an easily triggered internal compiler error in core
+       # networking code with '-march=native' on certain systems:
+       # https://github.com/llvm/llvm-project/issues/72026
+       # LLVM 19 introduces an optimization that resolves some high stack
+       # usage warnings that only appear wth '-march=native'.
+       depends on CC_IS_GCC || CLANG_VERSION >= 190100
 
 config X86_NATIVE_CPU
        bool "Build and optimize for local/native CPU"