1 #ifndef __LINUX_COMPILER_H 2 #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead." 3 #endif 4 5 /* 6 * Common definitions for all gcc versions go here. 7 */ 8 9 10 /* Optimization barrier */ 11 /* The "volatile" is due to gcc bugs */ 12 #define barrier() __asm__ __volatile__("": : :"memory") 13 14 /* 15 * This macro obfuscates arithmetic on a variable address so that gcc 16 * shouldn't recognize the original var, and make assumptions about it. 17 * 18 * This is needed because the C standard makes it undefined to do 19 * pointer arithmetic on "objects" outside their boundaries and the 20 * gcc optimizers assume this is the case. In particular they 21 * assume such arithmetic does not wrap. 22 * 23 * A miscompilation has been observed because of this on PPC. 24 * To work around it we hide the relationship of the pointer and the object 25 * using this macro. 26 * 27 * Versions of the ppc64 compiler before 4.1 had a bug where use of 28 * RELOC_HIDE could trash r30. The bug can be worked around by changing 29 * the inline assembly constraint from =g to =r, in this particular 30 * case either is valid. 31 */ 32 #define RELOC_HIDE(ptr, off) \ 33 ({ unsigned long __ptr; \ 34 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \ 35 (typeof(ptr)) (__ptr + (off)); }) 36 37 /* &a[0] degrades to a pointer: a different type from an array */ 38 #define __must_be_array(a) \ 39 BUILD_BUG_ON_ZERO(__builtin_types_compatible_p(typeof(a), typeof(&a[0]))) 40 41 /* 42 * Force always-inline if the user requests it so via the .config, 43 * or if gcc is too old: 44 */ 45 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ 46 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) 47 # define inline inline __attribute__((always_inline)) 48 # define __inline__ __inline__ __attribute__((always_inline)) 49 # define __inline __inline __attribute__((always_inline)) 50 #endif 51 52 #define __deprecated __attribute__((deprecated)) 53 #ifndef __packed 54 # define __packed __attribute__((packed)) 55 #endif 56 #define __weak __attribute__((weak)) 57 58 /* 59 * it doesn't make sense on ARM (currently the only user of __naked) to trace 60 * naked functions because then mcount is called without stack and frame pointer 61 * being set up and there is no chance to restore the lr register to the value 62 * before mcount was called. 63 */ 64 #define __naked __attribute__((naked)) notrace 65 66 #define __noreturn __attribute__((noreturn)) 67 68 /* 69 * From the GCC manual: 70 * 71 * Many functions have no effects except the return value and their 72 * return value depends only on the parameters and/or global 73 * variables. Such a function can be subject to common subexpression 74 * elimination and loop optimization just as an arithmetic operator 75 * would be. 76 * [...] 77 */ 78 #ifndef __pure 79 # define __pure __attribute__((pure)) 80 #endif 81 #ifndef __aligned 82 # define __aligned(x) __attribute__((aligned(x))) 83 #endif 84 #define __printf(a,b) __attribute__((format(printf,a,b))) 85 #define noinline __attribute__((noinline)) 86 #define __attribute_const__ __attribute__((__const__)) 87 #define __maybe_unused __attribute__((unused)) 88 #define __always_unused __attribute__((unused)) 89 90 #define __gcc_header(x) #x 91 #define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h) 92 #define gcc_header(x) _gcc_header(x) 93 #include gcc_header(__GNUC__) 94