linux-libre/include/linux/compiler-clang.h

#ifndef __LINUX_COMPILER_H
#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
 */

#ifdef uninitialized_var
#undef uninitialized_var
#define uninitialized_var(x) x = *(&(x))
#endif

/* same as gcc, this was present in clang-2.6 so we can assume it works
 * with any version that can compile the kernel
 */
#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)

/* Clang doesn't have a way to turn it off per-function, yet. */
#ifdef __noretpoline
#undef __noretpoline
#endif