include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR

Since commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive") clang no longer reuses the OPTIMIZER_HIDE_VAR macro
from compiler-gcc - instead it gets the version in
include/linux/compiler.h.  Unfortunately that version doesn't actually
prevent compiler from optimizing out the variable.

Fix up by moving the macro out from compiler-gcc.h to compiler.h.
Compilers without incline asm support will keep working
since it's protected by an ifdef.

Also fix up comments to match reality since we are no longer overriding
any macros.

Build-tested with gcc and clang.

Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 39f668d5066b0a8f4228b4d1504ae97760313944..333a6695a918c3dcea8402c054bb7a6069640cb0 100644 (file)
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -3,9 +3,8 @@
 #error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
 #endif
 
-/* Some compiler specific definitions are overwritten here
- * for Clang compiler
- */
+/* Compiler specific definitions for Clang compiler */
+
 #define uninitialized_var(x) x = *(&(x))
 
 /* same as gcc, this was present in clang-2.6 so we can assume it works

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 5776da43da9766a842e6170479deb2037418fcec..7b834e37d0c03d7502f08e8522b2c7d21ec11d1f 100644 (file)
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -58,10 +58,6 @@
        (typeof(ptr)) (__ptr + (off));                                  \
 })
 
-/* Make the optimizer believe the variable can be manipulated arbitrarily. */
-#define OPTIMIZER_HIDE_VAR(var)                                                \
-       __asm__ ("" : "=r" (var) : "0" (var))
-
 /*
  * A trick to suppress uninitialized variable warning without generating any
  * code

diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h
index 517bd14e122248f029d27e6dd192b492fe3be93b..b17f3cd18334df3d4958316a52177064ee4248d0 100644 (file)
--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -5,9 +5,7 @@
 
 #ifdef __ECC
 
-/* Some compiler specific definitions are overwritten here
- * for Intel ECC compiler
- */
+/* Compiler specific definitions for Intel ECC compiler */
 
 #include <asm/intrinsics.h>
 

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index fc5004a4b07d7b5b546e07f7d952fd1094892ead..445348facea97d2755f371198ca5730302c3f1ba 100644 (file)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -161,7 +161,9 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 #endif
 
 #ifndef OPTIMIZER_HIDE_VAR
-#define OPTIMIZER_HIDE_VAR(var) barrier()
+/* Make the optimizer believe the variable can be manipulated arbitrarily. */
+#define OPTIMIZER_HIDE_VAR(var)                                                \
+       __asm__ ("" : "=r" (var) : "0" (var))
 #endif
 
 /* Not-quite-unique ID. */