/* Never include this file directly.  Include <linux/compiler.h> instead.  */

/*
 * Common definitions for all gcc versions go here.
 */


/* Optimization barrier */
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")

/* This macro obfuscates arithmetic on a variable address so that gcc
   shouldn't recognize the original var, and make assumptions about it */
/*
 * Versions of the ppc64 compiler before 4.1 had a bug where use of
 * RELOC_HIDE could trash r30. The bug can be worked around by changing
 * the inline assembly constraint from =g to =r, in this particular
 * case either is valid.
 */
#define RELOC_HIDE(ptr, off)					\
  ({ unsigned long __ptr;					\
    __asm__ ("" : "=r"(__ptr) : "0"(ptr));		\
    (typeof(ptr)) (__ptr + (off)); })


#define inline		inline		__attribute__((always_inline))
#define __inline__	__inline__	__attribute__((always_inline))
#define __inline	__inline	__attribute__((always_inline))
#define __deprecated			__attribute__((deprecated))
#define  noinline			__attribute__((noinline))
#define __attribute_pure__		__attribute__((pure))
#define __attribute_const__		__attribute__((__const__))

/* Never include this file directly.  Include <linux/compiler.h> instead.  */

/*
 * Common definitions for all gcc versions go here.
 */


/* Optimization barrier */
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")

/* This macro obfuscates arithmetic on a variable address so that gcc
   shouldn't recognize the original var, and make assumptions about it */
#define RELOC_HIDE(ptr, off)					\
  ({ unsigned long __ptr;					\
    __asm__ ("" : "=g"(__ptr) : "0"(ptr));		\
    (typeof(ptr)) (__ptr + (off)); })


#define inline		inline		__attribute__((always_inline))
#define __inline__	__inline__	__attribute__((always_inline))
#define __inline	__inline	__attribute__((always_inline))
#define __deprecated			__attribute__((deprecated))
#define  noinline			__attribute__((noinline))
#define __attribute_pure__		__attribute__((pure))
#define __attribute_const__		__attribute__((__const__))

--- 
+++ 
@@ -11,9 +11,15 @@
 
 /* This macro obfuscates arithmetic on a variable address so that gcc
    shouldn't recognize the original var, and make assumptions about it */
+/*
+ * Versions of the ppc64 compiler before 4.1 had a bug where use of
+ * RELOC_HIDE could trash r30. The bug can be worked around by changing
+ * the inline assembly constraint from =g to =r, in this particular
+ * case either is valid.
+ */
 #define RELOC_HIDE(ptr, off)					\
   ({ unsigned long __ptr;					\
-    __asm__ ("" : "=g"(__ptr) : "0"(ptr));		\
+    __asm__ ("" : "=r"(__ptr) : "0"(ptr));		\
     (typeof(ptr)) (__ptr + (off)); })
 
 
[PATCH] Work around ppc64 compiler bug

In the process of optimising our per cpu data code, I found a ppc64
compiler bug that has been around forever. Basically the current
RELOC_HIDE can end up trashing r30. Details of the bug can be found at

  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25572

This bug is present in all compilers before 4.1. It is masked by the
fact that our current per cpu data code is inefficient and causes
other loads that end up marking r30 as used.

A workaround identified by Alan Modra is to use the =r asm constraint
instead of =g.

Signed-off-by: Anton Blanchard <14deb5e5e417133e888bf47bb6a3555c9bb7d81c@samba.org>
[ Verified that this makes no real difference on x86[-64] */
Signed-off-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@osdl.org>
