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SubjectRe: [PATCH 1/3] tools compiler.h: Add attribute to disable tail calls
Em Sat, May 30, 2020 at 01:20:13AM -0700, Ian Rogers escreveu:
> Tail call optimizations can remove stack frames that are used in
> unwinding tests. Add an attribute that can be used to disable the tail
> call optimization. Tested on clang and GCC.
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
> tools/include/linux/compiler-gcc.h | 8 ++++++++
> tools/include/linux/compiler.h | 3 +++
> 2 files changed, 11 insertions(+)
>
> diff --git a/tools/include/linux/compiler-gcc.h b/tools/include/linux/compiler-gcc.h
> index 95c072b70d0e..cda555b47d3d 100644
> --- a/tools/include/linux/compiler-gcc.h
> +++ b/tools/include/linux/compiler-gcc.h
> @@ -27,6 +27,14 @@
> #define __pure __attribute__((pure))
> #endif
> #define noinline __attribute__((noinline))
> +#ifdef __has_attribute
> +#if __has_attribute(disable_tail_calls)
> +#define __no_tail_call __attribute__((disable_tail_calls))
> +#endif
> +#endif
> +#ifndef __no_tail_call
> +#define __no_tail_call __attribute__((optimize("no-optimize-sibling-calls")))
> +#endif

Added this for some retro-computing old distros when building with old
clang versions :-)

- Arnaldo

diff --git a/tools/include/linux/compiler-gcc.h b/tools/include/linux/compiler-gcc.h
index cda555b47d3d..dea7378ad646 100644
--- a/tools/include/linux/compiler-gcc.h
+++ b/tools/include/linux/compiler-gcc.h
@@ -33,7 +33,10 @@
#endif
#endif
#ifndef __no_tail_call
+#if GCC_VERSION > 40201
#define __no_tail_call __attribute__((optimize("no-optimize-sibling-calls")))
+#else
+#define __no_tail_call
#endif
#ifndef __packed
#define __packed __attribute__((packed))
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