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/20201028081123.GT2628@hirez.programming.kicks-ass.net/
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/20201114000803.909530-1-irogers@google.com/
    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 <irogers@google.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: clang-built-linux@googlegroups.com
Link: http://lore.kernel.org/lkml/20210922173812.456348-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

0 files changed, 0 insertions, 0 deletions