perf test: Fix DWARF unwind for optimized builds.

To ensure the stack frames are on the stack tail calls optimizations
need to be inhibited. If your compiler supports an attribute use it,
otherwise use an asm volatile barrier.

The barrier fix was suggested here:
https://lore.kernel.org/lkml/[email protected]/
Tested with an optimized clang build and by forcing the asm barrier
route with an optimized clang build.

A GCC bug tracking a proper disable_tail_calls is:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97831

Fixes: 9ae1e990f1ab ("perf tools: Remove broken __no_tail_call
       attribute")

v2. is a rebase. The original fix patch generated quite a lot of
    discussion over the right place for the fix:
    https://lore.kernel.org/lkml/[email protected]/
    The patch reflects my preference of it being near the use, so that
    future code cleanups don't break this somewhat special usage.

Signed-off-by: Ian Rogers <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: [email protected]
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

0 files changed, 0 insertions, 0 deletions