Re: [XEN PATCH] xen: Drop logic for old clang versions.

["Roger Pau Monné" <roger.pau@citrix.com>]

On Sun, Aug 10, 2025 at 03:03:53PM +0200, nicola.vetrini@gmail.com wrote:
> From: Nicola Vetrini <nicola.vetrini@bugseng.com>
> 
> The enforced toolchain baseline for clang is version 11,
> therefore this logic is effectively dead code.
> 
> No functional change.
> 
> Signed-off-by: Nicola Vetrini <nicola.vetrini@gmail.com>

Acked-by: Roger Pau Monné <roger.pau@citrix.com>

> ---
> Mentioned in https://gitlab.com/xen-project/xen/-/issues/201
> ---
>  xen/common/coverage/llvm.c   | 4 ----
>  xen/include/xen/self-tests.h | 9 +--------
>  2 files changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/xen/common/coverage/llvm.c b/xen/common/coverage/llvm.c
> index 50d7a3c5d301..517b2aa8c202 100644
> --- a/xen/common/coverage/llvm.c
> +++ b/xen/common/coverage/llvm.c
> @@ -44,12 +44,8 @@
>      ((uint64_t)'f' << 16) | ((uint64_t)'R' << 8)  | ((uint64_t)129)
>  #endif
>  
> -#if __clang_major__ >= 4 || (__clang_major__ == 3 && __clang_minor__ >= 9)
>  #define LLVM_PROFILE_VERSION    4
>  #define LLVM_PROFILE_NUM_KINDS  2
> -#else
> -#error "clang version not supported with coverage"
> -#endif

Rant: most of the LLVM coverage stuff is already kind of dead code, as
the format of the data changes between versions and there's no way for
LLVM to generate the blob itself using a builtin function or
similar.  We haven't kept up with new formats, and now it's not
possible to parse the output coverage data when using newish LLVM
versions.

Linux converts it's LLVM coverage data to gcov format (which AFAIK is
way more stable), and exports it in gcov format.  We should consider
importing that from Linux.

Thanks, Roger.