include/linux/compiler.h

Source file repositories/reference/linux-study-clean/include/linux/compiler.h

File Facts

System
Linux kernel
Corpus path
include/linux/compiler.h
Extension
.h
Size
13352 bytes
Lines
372
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef __LINUX_COMPILER_H
#define __LINUX_COMPILER_H

#include <linux/compiler_types.h>

#ifndef __ASSEMBLY__

#ifdef __KERNEL__

/*
 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
 * to disable branch tracing on a per file basis.
 */
void ftrace_likely_update(struct ftrace_likely_data *f, int val,
			  int expect, int is_constant);
#if defined(CONFIG_TRACE_BRANCH_PROFILING) \
    && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
#define likely_notrace(x)	__builtin_expect(!!(x), 1)
#define unlikely_notrace(x)	__builtin_expect(!!(x), 0)

#define __branch_check__(x, expect, is_constant) ({			\
			long ______r;					\
			static struct ftrace_likely_data		\
				__aligned(4)				\
				__section("_ftrace_annotated_branch")	\
				______f = {				\
				.data.func = __func__,			\
				.data.file = __FILE__,			\
				.data.line = __LINE__,			\
			};						\
			______r = __builtin_expect(!!(x), expect);	\
			ftrace_likely_update(&______f, ______r,		\
					     expect, is_constant);	\
			______r;					\
		})

/*
 * Using __builtin_constant_p(x) to ignore cases where the return
 * value is always the same.  This idea is taken from a similar patch
 * written by Daniel Walker.
 */
# ifndef likely
#  define likely(x)	(__branch_check__(x, 1, __builtin_constant_p(x)))
# endif
# ifndef unlikely
#  define unlikely(x)	(__branch_check__(x, 0, __builtin_constant_p(x)))
# endif

#ifdef CONFIG_PROFILE_ALL_BRANCHES
/*
 * "Define 'is'", Bill Clinton
 * "Define 'if'", Steven Rostedt
 */
#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )

#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))

#define __trace_if_value(cond) ({			\
	static struct ftrace_branch_data		\
		__aligned(4)				\
		__section("_ftrace_branch")		\
		__if_trace = {				\
			.func = __func__,		\
			.file = __FILE__,		\
			.line = __LINE__,		\
		};					\
	(cond) ?					\
		(__if_trace.miss_hit[1]++,1) :		\
		(__if_trace.miss_hit[0]++,0);		\
})

#endif /* CONFIG_PROFILE_ALL_BRANCHES */

#else
# define likely(x)	__builtin_expect(!!(x), 1)
# define unlikely(x)	__builtin_expect(!!(x), 0)
# define likely_notrace(x)	likely(x)
# define unlikely_notrace(x)	unlikely(x)
#endif

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

#ifndef barrier_data
/*
 * This version is i.e. to prevent dead stores elimination on @ptr
 * where gcc and llvm may behave differently when otherwise using

Annotation

Implementation Notes