[PATCH] x86: mark BUG()s and assertion failures as terminal.

[Tim Deegan <tim@xen.org>]

This helps avoid static analysis false-positives, and might lead to
better code density as the compiler knows it doesn't have to restore
spilled state &c.

Signed-off-by: Tim Deegan <tim@xen.org>
---
 xen/include/asm-x86/bug.h  |   11 ++++++++---
 xen/include/xen/compiler.h |    6 ++++++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/xen/include/asm-x86/bug.h b/xen/include/asm-x86/bug.h
index e5dd559..956bfd2 100644
--- a/xen/include/asm-x86/bug.h
+++ b/xen/include/asm-x86/bug.h
@@ -46,12 +46,17 @@ struct bug_frame {
 
 
 #define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 0, NULL)
-#define BUG()  BUG_FRAME(BUGFRAME_bug,  __LINE__, __FILE__, 0, NULL)
+#define BUG() do {                                              \
+    BUG_FRAME(BUGFRAME_bug,  __LINE__, __FILE__, 0, NULL);      \
+    unreachable();                                              \
+} while (0)
 
 #define run_in_exception_handler(fn) BUG_FRAME(BUGFRAME_run_fn, 0, fn, 0, NULL)
 
-#define assert_failed(msg)                                      \
-    BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg)
+#define assert_failed(msg) do {                                 \
+    BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg);     \
+    unreachable();                                              \
+} while (0)
 
 extern const struct bug_frame __start_bug_frames[],
                               __stop_bug_frames_0[],
diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
index 7009a09..7d6805c 100644
--- a/xen/include/xen/compiler.h
+++ b/xen/include/xen/compiler.h
@@ -14,6 +14,12 @@
 #define always_inline __inline__ __attribute__ ((always_inline))
 #define noinline      __attribute__((noinline))
 
+#if (!defined(__clang__) && (__GNUC__ == 4) && (__GNUC_MINOR__ < 5))
+#define unreachable() do {} while (1)
+#else
+#define unreachable() __builtin_unreachable()
+#endif
+
 #ifdef __clang__
 /* Clang can replace some vars with new automatic ones that go in .data;
  * mark all explicit-segment vars 'used' to prevent that. */
-- 
1.7.10.4