linux-kernel - [PATCH 1/3] tools compiler.h: Add attribute to disable tail calls

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Message-Id: <20200530082015.39162-2-irogers@google.com>
Date:   Sat, 30 May 2020 01:20:13 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Cc:     Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 1/3] 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.

Signed-off-by: Ian Rogers <irogers@...gle.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
 #ifndef __packed
 #define __packed	__attribute__((packed))
 #endif
diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 180f7714a5f1..9f9002734e19 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
-- 
2.27.0.rc2.251.g90737beb825-goog