Merge branch 'bugfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6

[linux-2.6.git] / include / linux / compiler-gcc.h

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 03ec2311fb29c9ce4d252e2e9b41b8eea19e8e18..cb4c1eb7778e4f776bf9343f93d5f9c8636ab148 100644 (file)
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -1,4 +1,6 @@
-/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
+#endif
 
 /*
  * Common definitions for all gcc versions go here.
@@ -9,9 +11,19 @@
 /* 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 */
 /*
+ * This macro obfuscates arithmetic on a variable address so that gcc
+ * shouldn't recognize the original var, and make assumptions about it.
+ *
+ * This is needed because the C standard makes it undefined to do
+ * pointer arithmetic on "objects" outside their boundaries and the
+ * gcc optimizers assume this is the case. In particular they
+ * assume such arithmetic does not wrap.
+ *
+ * A miscompilation has been observed because of this on PPC.
+ * To work around it we hide the relationship of the pointer and the object
+ * using this macro.
+ *
  * 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
@@ -23,21 +35,68 @@
     (typeof(ptr)) (__ptr + (off)); })
 
 /* &a[0] degrades to a pointer: a different type from an array */
-#define __must_be_array(a) \
-  BUILD_BUG_ON_ZERO(__builtin_types_compatible_p(typeof(a), typeof(&a[0])))
+#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
+
+/*
+ * Force always-inline if the user requests it so via the .config,
+ * or if gcc is too old:
+ */
+#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
+    !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
+# define inline                inline          __attribute__((always_inline))
+# define __inline__    __inline__      __attribute__((always_inline))
+# define __inline      __inline        __attribute__((always_inline))
+#endif
 
-#define inline         inline          __attribute__((always_inline))
-#define __inline__     __inline__      __attribute__((always_inline))
-#define __inline       __inline        __attribute__((always_inline))
 #define __deprecated                   __attribute__((deprecated))
 #define __packed                       __attribute__((packed))
 #define __weak                         __attribute__((weak))
-#define __naked                                __attribute__((naked))
+
+/*
+ * it doesn't make sense on ARM (currently the only user of __naked) to trace
+ * naked functions because then mcount is called without stack and frame pointer
+ * being set up and there is no chance to restore the lr register to the value
+ * before mcount was called.
+ *
+ * The asm() bodies of naked functions often depend on standard calling conventions,
+ * therefore they must be noinline and noclone.  GCC 4.[56] currently fail to enforce
+ * this, so we must do so ourselves.  See GCC PR44290.
+ */
+#define __naked                                __attribute__((naked)) noinline __noclone notrace
+
 #define __noreturn                     __attribute__((noreturn))
+
+/*
+ * From the GCC manual:
+ *
+ * Many functions have no effects except the return value and their
+ * return value depends only on the parameters and/or global
+ * variables.  Such a function can be subject to common subexpression
+ * elimination and loop optimization just as an arithmetic operator
+ * would be.
+ * [...]
+ */
 #define __pure                         __attribute__((pure))
 #define __aligned(x)                   __attribute__((aligned(x)))
 #define __printf(a,b)                  __attribute__((format(printf,a,b)))
 #define  noinline                      __attribute__((noinline))
-#define __attribute_pure__             __attribute__((pure))
 #define __attribute_const__            __attribute__((__const__))
 #define __maybe_unused                 __attribute__((unused))
+#define __always_unused                        __attribute__((unused))
+
+#define __gcc_header(x) #x
+#define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h)
+#define gcc_header(x) _gcc_header(x)
+#include gcc_header(__GNUC__)
+
+#if !defined(__noclone)
+#define __noclone      /* not needed */
+#endif
+
+/*
+ * A trick to suppress uninitialized variable warning without generating any
+ * code
+ */
+#define uninitialized_var(x) x = x
+
+#define __always_inline                inline __attribute__((always_inline))