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) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 39 40 /* 41 * Force always-inline if the user requests it so via the .config, 42 * or if gcc is too old: 43 */ 44 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ 45 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) 46 # define inline inline __attribute__((always_inline)) 47 # define __inline__ __inline__ __attribute__((always_inline)) 48 # define __inline __inline __attribute__((always_inline)) 49 #endif 50 51 #define __deprecated __attribute__((deprecated)) 52 #define __packed __attribute__((packed)) 53 #define __weak __attribute__((weak)) 54 55 /* 56 * it doesn't make sense on ARM (currently the only user of __naked) to trace 57 * naked functions because then mcount is called without stack and frame pointer 58 * being set up and there is no chance to restore the lr register to the value 59 * before mcount was called. 60 * 61 * The asm() bodies of naked functions often depend on standard calling conventions, 62 * therefore they must be noinline and noclone. GCC 4.[56] currently fail to enforce 63 * this, so we must do so ourselves. See GCC PR44290. 64 */ 65 #define __naked __attribute__((naked)) noinline __noclone notrace 66 67 #define __noreturn __attribute__((noreturn)) 68 69 /* 70 * From the GCC manual: 71 * 72 * Many functions have no effects except the return value and their 73 * return value depends only on the parameters and/or global 74 * variables. Such a function can be subject to common subexpression 75 * elimination and loop optimization just as an arithmetic operator 76 * would be. 77 * [...] 78 */ 79 #define __pure __attribute__((pure)) 80 #define __aligned(x) __attribute__((aligned(x))) 81 #define __printf(a,b) __attribute__((format(printf,a,b))) 82 #define noinline __attribute__((noinline)) 83 #define __attribute_const__ __attribute__((__const__)) 84 #define __maybe_unused __attribute__((unused)) 85 #define __always_unused __attribute__((unused)) 86 87 #define __gcc_header(x) #x 88 #define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h) 89 #define gcc_header(x) _gcc_header(x) 90 #include gcc_header(__GNUC__) 91 92 #if !defined(__noclone) 93 #define __noclone /* not needed */ 94 #endif 95 96 /* 97 * A trick to suppress uninitialized variable warning without generating any 98 * code 99 */ 100 #define uninitialized_var(x) x = x 101 102 #define __always_inline inline __attribute__((always_inline)) 103