Hi,
On 15/12/2020 11:46, Jan Beulich wrote:
On 15.12.2020 12:26, Julien Grall wrote:
--- a/xen/include/xen/lib.h
+++ b/xen/include/xen/lib.h
@@ -23,7 +23,13 @@
#include <asm/bug.h>
#define BUG_ON(p) do { if (unlikely(p)) BUG(); } while (0)
-#define WARN_ON(p) do { if (unlikely(p)) WARN(); } while (0)
+#define WARN_ON(p) ({ \
+ bool __ret_warn_on = (p); \
Please can you avoid leading underscores here?
I can.
+ \
+ if ( unlikely(__ret_warn_on) ) \
+ WARN(); \
+ unlikely(__ret_warn_on); \
+})
Is this latter unlikely() having any effect? So far I thought it
would need to be immediately inside a control construct or be an
operand to && or ||.
The unlikely() is directly taken from the Linux implementation.
My guess is the compiler is still able to use the information for the
branch prediction in the case of:
if ( WARN_ON(...) )
Cheers,
Jan
--
Julien Grall
