From: Ian Rogers <irogers@google.com>
Date: Sat, 30 May 2020 08:20:13 +0000 (-0700)
Subject: tools compiler.h: Add attribute to disable tail calls
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=21f2b7c13335eeec498569927d87c7381c3b54fa;p=linux.git

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 95c072b70d0e8..b9d4322e1e655 100644
--- 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 180f7714a5f10..9f9002734e192 100644
--- 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