tools compiler.h: Add attribute to disable tail calls

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.

Committer notes:

Old versions of clang don't like that __attribute__((optimize)), so add
an ifdef to make it go away.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: clang-built-linux@googlegroups.com
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Monnet <quentin@isovalent.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200530082015.39162-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/include/linux/compiler-gcc.h b/tools/include/linux/compiler-gcc.h
index 95c072b..b9d4322 100644 (file)
--- a/tools/include/linux/compiler-gcc.h
+++ b/tools/include/linux/compiler-gcc.h
@@ -27,6 +27,18 @@
 #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
+#if GCC_VERSION > 40201
+#define __no_tail_call __attribute__((optimize("no-optimize-sibling-calls")))
+#else
+#define __no_tail_call
+#endif
+#endif
 #ifndef __packed
 #define __packed       __attribute__((packed))
 #endif

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 180f771..9f90027 100644 (file)
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -47,6 +47,9 @@
 #ifndef noinline
 #define noinline
 #endif
+#ifndef __no_tail_call
+#define __no_tail_call
+#endif
 
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #ifndef __same_type