1 #ifndef __LINUX_COMPILER_H
2 #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
6 * Common definitions for all gcc versions go here.
8 #define GCC_VERSION (__GNUC__ * 10000 \
9 + __GNUC_MINOR__ * 100 \
10 + __GNUC_PATCHLEVEL__)
12 /* Optimization barrier */
14 /* The "volatile" is due to gcc bugs */
15 #define barrier() __asm__ __volatile__("": : :"memory")
17 * This version is i.e. to prevent dead stores elimination on @ptr
18 * where gcc and llvm may behave differently when otherwise using
19 * normal barrier(): while gcc behavior gets along with a normal
20 * barrier(), llvm needs an explicit input variable to be assumed
21 * clobbered. The issue is as follows: while the inline asm might
22 * access any memory it wants, the compiler could have fit all of
23 * @ptr into memory registers instead, and since @ptr never escaped
24 * from that, it proofed that the inline asm wasn't touching any of
25 * it. This version works well with both compilers, i.e. we're telling
26 * the compiler that the inline asm absolutely may see the contents
27 * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
29 #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
32 * This macro obfuscates arithmetic on a variable address so that gcc
33 * shouldn't recognize the original var, and make assumptions about it.
35 * This is needed because the C standard makes it undefined to do
36 * pointer arithmetic on "objects" outside their boundaries and the
37 * gcc optimizers assume this is the case. In particular they
38 * assume such arithmetic does not wrap.
40 * A miscompilation has been observed because of this on PPC.
41 * To work around it we hide the relationship of the pointer and the object
44 * Versions of the ppc64 compiler before 4.1 had a bug where use of
45 * RELOC_HIDE could trash r30. The bug can be worked around by changing
46 * the inline assembly constraint from =g to =r, in this particular
47 * case either is valid.
49 #define RELOC_HIDE(ptr, off) \
51 unsigned long __ptr; \
52 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
53 (typeof(ptr)) (__ptr + (off)); \
56 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
57 #define OPTIMIZER_HIDE_VAR(var) \
58 __asm__ ("" : "=r" (var) : "0" (var))
61 #define __must_be_array(a) 0
63 /* &a[0] degrades to a pointer: a different type from an array */
64 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
68 * Force always-inline if the user requests it so via the .config,
69 * or if gcc is too old:
71 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
72 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
73 #define inline inline __attribute__((always_inline)) notrace
74 #define __inline__ __inline__ __attribute__((always_inline)) notrace
75 #define __inline __inline __attribute__((always_inline)) notrace
77 /* A lot of inline functions can cause havoc with function tracing */
78 #define inline inline notrace
79 #define __inline__ __inline__ notrace
80 #define __inline __inline notrace
83 #define __always_inline inline __attribute__((always_inline))
84 #define noinline __attribute__((noinline))
86 #define __deprecated __attribute__((deprecated))
87 #define __packed __attribute__((packed))
88 #define __weak __attribute__((weak))
89 #define __alias(symbol) __attribute__((alias(#symbol)))
92 * it doesn't make sense on ARM (currently the only user of __naked)
93 * to trace naked functions because then mcount is called without
94 * stack and frame pointer being set up and there is no chance to
95 * restore the lr register to the value before mcount was called.
97 * The asm() bodies of naked functions often depend on standard calling
98 * conventions, therefore they must be noinline and noclone.
100 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
103 #define __naked __attribute__((naked)) noinline __noclone notrace
105 #define __noreturn __attribute__((noreturn))
108 * From the GCC manual:
110 * Many functions have no effects except the return value and their
111 * return value depends only on the parameters and/or global
112 * variables. Such a function can be subject to common subexpression
113 * elimination and loop optimization just as an arithmetic operator
117 #define __pure __attribute__((pure))
118 #define __aligned(x) __attribute__((aligned(x)))
119 #define __printf(a, b) __attribute__((format(printf, a, b)))
120 #define __scanf(a, b) __attribute__((format(scanf, a, b)))
121 #define __attribute_const__ __attribute__((__const__))
122 #define __maybe_unused __attribute__((unused))
123 #define __always_unused __attribute__((unused))
125 #define __gcc_header(x) #x
126 #define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h)
127 #define gcc_header(x) _gcc_header(x)
128 #include gcc_header(__GNUC__)
130 #if !defined(__noclone)
131 #define __noclone /* not needed */
135 * A trick to suppress uninitialized variable warning without generating any
138 #define uninitialized_var(x) x = x