[PATCH] ECC support

From: "Nakajima, Jun" <jun.nakajima@intel.com>

Split the increasingly messy compiler.h file into per-compiler files and also
add support for non-gcc compilers.  

With the current implementation:

  include/linux/compiler.h defines the compiler-dependent abstractions
  which can be overwritten by per-compiler definitions.

  include/linux/compiler-gcc.h contains the common definitions for all gcc
  versions.

  include/linux/compiler-gcc[2,3,+].h contains gcc major version specific
  definitions.

  include/linux/compiler-intel.h contains intel compiler specific
  definitions."

include/linux/compiler-gcc+.h

+/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+
+/*
+ * These definitions are for Ueber-GCC: always newer than the latest
+ * version and hence sporting everything plus a kitchen-sink.
+ */
+#include <linux/compiler-gcc.h>
+
+#define inline			__inline__ __attribute__((always_inline))
+#define __inline__		__inline__ __attribute__((always_inline))
+#define __inline		__inline__ __attribute__((always_inline))
+#define __deprecated		__attribute__((deprecated))
+#define __attribute_used__	__attribute__((__used__))
+#define __attribute_pure__	__attribute__((pure))

include/linux/compiler-gcc.h

+/* 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)); })

include/linux/compiler-gcc2.h

+/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+
+/* These definitions are for GCC v2.x.  */
+
+/* Somewhere in the middle of the GCC 2.96 development cycle, we implemented
+   a mechanism by which the user can annotate likely branch directions and
+   expect the blocks to be reordered appropriately.  Define __builtin_expect
+   to nothing for earlier compilers.  */
+#include <linux/compiler-gcc.h>
+
+#if __GNUC_MINOR__ < 96
+# define __builtin_expect(x, expected_value) (x)
+#endif
+
+#define __attribute_used__	__attribute__((__unused__))
+
+/*
+ * The attribute `pure' is not implemented in GCC versions earlier
+ * than 2.96.
+ */
+#if __GNUC_MINOR__ >= 96
+# define __attribute_pure__	__attribute__((pure))
+#endif

include/linux/compiler-gcc3.h

+/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+
+/* These definitions are for GCC v3.x.  */
+#include <linux/compiler-gcc.h>
+
+#if __GNUC_MINOR__ >= 1
+# define inline		__inline__ __attribute__((always_inline))
+# define __inline__	__inline__ __attribute__((always_inline))
+# define __inline	__inline__ __attribute__((always_inline))
+#endif
+
+#if __GNUC_MINOR__ > 0
+# define __deprecated	__attribute__((deprecated))
+#endif
+
+#if __GNUC_MINOR__ >= 3
+# define __attribute_used__	__attribute__((__used__))
+#else
+# define __attribute_used__	__attribute__((__unused__))
+#endif
+
+#define __attribute_pure__	__attribute__((pure))

include/linux/compiler-intel.h

+/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+
+#ifdef __ECC
+
+/* Some compiler specific definitions are overwritten here
+ * for Intel ECC compiler
+ */
+
+#include <asm/intrinsics.h>
+
+/* Intel ECC compiler doesn't support gcc specific asm stmts.
+ * It uses intrinsics to do the equivalent things.
+ */
+#undef barrier
+#undef RELOC_HIDE
+
+#define barrier() __memory_barrier()
+
+#define RELOC_HIDE(ptr, off)					\
+  ({ unsigned long __ptr;					\
+     __ptr = (unsigned long) (ptr);				\
+    (typeof(ptr)) (__ptr + (off)); })
+
+#endif

include/linux/compiler.h

@@ -2,28 +2,36 @@
 #define __LINUX_COMPILER_H
 
 #ifdef __CHECKER__
-  #define __user	__attribute__((noderef, address_space(1)))
-  #define __kernel	/* default address space */
+# define __user		__attribute__((noderef, address_space(1)))
+# define __kernel	/* default address space */
 #else
-  #define __user
-  #define __kernel
+# define __user
+# define __kernel
 #endif
 
-#if (__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1)
-#define inline		__inline__ __attribute__((always_inline))
-#define __inline__	__inline__ __attribute__((always_inline))
-#define __inline	__inline__ __attribute__((always_inline))
+#if __GNUC__ > 3
+# include <linux/compiler-gcc+.h>	/* catch-all for GCC 4, 5, etc. */
+#elif __GNUC__ == 3
+# include <linux/compiler-gcc3.h>
+#elif __GNUC__ == 2
+# include <linux/compiler-gcc2.h>
+#else
+# error Sorry, your compiler is too old/not recognized.
 #endif
 
-/* Somewhere in the middle of the GCC 2.96 development cycle, we implemented
-   a mechanism by which the user can annotate likely branch directions and
-   expect the blocks to be reordered appropriately.  Define __builtin_expect
-   to nothing for earlier compilers.  */
-
-#if __GNUC__ == 2 && __GNUC_MINOR__ < 96
-#define __builtin_expect(x, expected_value) (x)
+/* Intel compiler defines __GNUC__. So we will overwrite implementations
+ * coming from above header files here
+ */
+#ifdef __INTEL_COMPILER
+# include <linux/compiler-intel.h>
 #endif
 
+/*
+ * Generic compiler-dependent macros required for kernel
+ * build go below this comment. Actual compiler/compiler version
+ * specific implementations come from the above header files
+ */
+
 #define likely(x)	__builtin_expect(!!(x), 1)
 #define unlikely(x)	__builtin_expect(!!(x), 0)
 
@@ -33,10 +41,8 @@
  * Usage is:
  * 		int __deprecated foo(void)
  */
-#if ( __GNUC__ == 3 && __GNUC_MINOR__ > 0 ) || __GNUC__ > 3
-#define __deprecated	__attribute__((deprecated))
-#else
-#define __deprecated
+#ifndef __deprecated
+# define __deprecated		/* unimplemented */
 #endif
 
 /*
@@ -50,10 +56,8 @@
  * In prior versions of gcc, such functions and data would be emitted, but
  * would be warned about except with attribute((unused)).
  */
-#if __GNUC__ == 3 && __GNUC_MINOR__ >= 3 || __GNUC__ > 3
-#define __attribute_used__	__attribute__((__used__))
-#else
-#define __attribute_used__	__attribute__((__unused__))
+#ifndef __attribute_used__
+# define __attribute_used__	/* unimplemented */
 #endif
 
 /*
@@ -65,19 +69,21 @@
  * elimination and loop optimization just as an arithmetic operator
  * would be.
  * [...]
- * The attribute `pure' is not implemented in GCC versions earlier
- * than 2.96.
  */
-#if (__GNUC__ == 2 && __GNUC_MINOR__ >= 96) || __GNUC__ > 2
-#define __attribute_pure__	__attribute__((pure))
-#else
-#define __attribute_pure__	/* unimplemented */
+#ifndef __attribute_pure__
+# define __attribute_pure__	/* unimplemented */
+#endif
+
+/* Optimization barrier */
+#ifndef barrier
+# define barrier() __memory_barrier()
 #endif
 
-/* 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)					\
+#ifndef RELOC_HIDE
+# define RELOC_HIDE(ptr, off)					\
   ({ unsigned long __ptr;					\
-    __asm__ ("" : "=g"(__ptr) : "0"(ptr));		\
+     __ptr = (unsigned long) (ptr);				\
     (typeof(ptr)) (__ptr + (off)); })
+#endif
+
 #endif /* __LINUX_COMPILER_H */

include/linux/kernel.h

@@ -15,10 +15,6 @@
 #include <asm/byteorder.h>
 #include <asm/bug.h>
 
-/* Optimization barrier */
-/* The "volatile" is due to gcc bugs */
-#define barrier() __asm__ __volatile__("": : :"memory")
-
 #define INT_MAX		((int)(~0U>>1))
 #define INT_MIN		(-INT_MAX - 1)
 #define UINT_MAX	(~0U)