/*
* compiler.h
*
+ * Compiler-specific definitions. Currently, only GCC and clang are supported.
+ *
* The author dedicates this file to the public domain.
* You can do whatever you want with this file.
*/
#ifndef _WIMLIB_COMPILER_H
#define _WIMLIB_COMPILER_H
-#ifdef __GNUC__
-# include "wimlib/compiler-gcc.h"
-#else
-# error "Unrecognized compiler. Please add a header file for your compiler."
-#endif
+/* Is the compiler GCC of the specified version or later? This always returns
+ * false for clang, since clang is "frozen" at GNUC 4.2. The __has_*
+ * feature-test macros should be used to detect clang functionality instead. */
+#define GCC_PREREQ(major, minor) \
+ (!defined(__clang__) && !defined(__INTEL_COMPILER) && \
+ (__GNUC__ > major || \
+ (__GNUC__ == major && __GNUC_MINOR__ >= minor)))
-#ifndef WIMLIBAPI
-# define WIMLIBAPI
+/* Feature-test macros defined by recent versions of clang. */
+#ifndef __has_attribute
+# define __has_attribute(attribute) 0
#endif
-
-#ifndef _packed_attribute
-# error "missing required definition of _packed_attribute"
+#ifndef __has_feature
+# define __has_feature(feature) 0
#endif
-
-#ifndef _aligned_attribute
-# error "missing required definition of _aligned_attribute"
+#ifndef __has_builtin
+# define __has_builtin(builtin) 0
#endif
-#ifndef _may_alias_attribute
-# error "missing required definition of _may_alias_attribute"
+/* Declare that the annotated function should be exported from the shared
+ * library (or DLL). */
+#ifdef __WIN32__
+# define WIMLIBAPI __declspec(dllexport)
+#else
+# define WIMLIBAPI __attribute__((visibility("default")))
#endif
-#ifndef likely
-# define likely(expr) (expr)
-#endif
+/* Declare that the annotated function should be inlined. Currently, we force
+ * the compiler to honor this because we use 'inline' in highly tuned code, e.g.
+ * compression codecs. */
+#define inline inline __attribute__((always_inline))
-#ifndef unlikely
-# define unlikely(expr) (expr)
-#endif
+/* Declare that the annotated function should *not* be inlined. */
+#define noinline __attribute__((noinline))
-#ifndef prefetch
-# define prefetch(addr)
-#endif
+/* Functionally the same as 'noinline', but documents that the reason for not
+ * inlining is to prevent the annotated function from being inlined into a
+ * recursive function, thereby increasing its stack usage. */
+#define noinline_for_stack noinline
+
+/* Hint that the expression is usually true. */
+#define likely(expr) __builtin_expect(!!(expr), 1)
+
+/* Hint that the expression is usually false. */
+#define unlikely(expr) __builtin_expect(!!(expr), 0)
+
+/* Prefetch into L1 cache for read. */
+#define prefetchr(addr) __builtin_prefetch((addr), 0)
+
+/* Prefetch into L1 cache for write. */
+#define prefetchw(addr) __builtin_prefetch((addr), 1)
+
+/* Declare that the members of the annotated struct are tightly packed, and the
+ * struct itself may be misaligned. */
+#define _packed_attribute __attribute__((packed))
+
+/* Declare that the annotated variable, or variables of the annotated type, are
+ * to be aligned on n-byte boundaries. */
+#define _aligned_attribute(n) __attribute__((aligned(n)))
-#ifndef _cold_attribute
+/* Declare that pointers to the annotated type may alias other pointers. */
+#define _may_alias_attribute __attribute__((may_alias))
+
+/* Hint that the annotated function is rarely called. */
+#if GCC_PREREQ(4, 4) || __has_attribute(cold)
+# define _cold_attribute __attribute__((cold))
+#else
# define _cold_attribute
#endif
-#ifndef _malloc_attribute
-# define _malloc_attribute
-#endif
+/* Hint that the annotated function is malloc-like: any non-null pointer it
+ * returns will not alias any pointer previously in use by the program. */
+#define _malloc_attribute __attribute__((malloc))
+
+/* TODO: _format_attribute is currently ignored. */
+#define _format_attribute(type, format_str, format_start)
-#ifndef _format_attribute
-# define _format_attribute(type, format_str, format_start)
+/* Hint that the annotated function is intentionally not used. This might be
+ * the case if the function contains only static assertions. */
+#define _unused_attribute __attribute__((unused))
+
+/* Endianness definitions. Either CPU_IS_BIG_ENDIAN or CPU_IS_LITTLE_ENDIAN is
+ * set to 1. The other is set to 0. Note that newer gcc supports
+ * __BYTE_ORDER__ for easily determining the endianness; older gcc doesn't. In
+ * the latter case we fall back to a configure-time check. */
+#ifdef __BYTE_ORDER__
+# define CPU_IS_BIG_ENDIAN (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+#elif defined(HAVE_CONFIG_H)
+# include "config.h"
+# ifdef WORDS_BIGENDIAN
+# define CPU_IS_BIG_ENDIAN 1
+# else
+# define CPU_IS_BIG_ENDIAN 0
+# endif
#endif
+#define CPU_IS_LITTLE_ENDIAN (!CPU_IS_BIG_ENDIAN)
-#ifndef noinline
-# define noinline
+/* UNALIGNED_ACCESS_IS_FAST should be defined to 1 if unaligned memory accesses
+ * can be performed efficiently on the target platform. */
+#if defined(__x86_64__) || defined(__i386__) || defined(__ARM_FEATURE_UNALIGNED)
+# define UNALIGNED_ACCESS_IS_FAST 1
+#else
+# define UNALIGNED_ACCESS_IS_FAST 0
#endif
-#ifndef CPU_IS_BIG_ENDIAN
-# error "missing required endianness definition"
+/* Get the type of the specified expression. */
+#define typeof __typeof__
+
+/* Get the minimum of two variables, without multiple evaluation. */
+#ifndef min
+# define min(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
+ (_a < _b) ? _a : _b; })
#endif
-#define CPU_IS_LITTLE_ENDIAN (!CPU_IS_BIG_ENDIAN)
+/* Get the maximum of two variables, without multiple evaluation. */
+#ifndef max
+# define max(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); \
+ (_a > _b) ? _a : _b; })
+#endif
-#ifndef UNALIGNED_ACCESS_SPEED
-# define UNALIGNED_ACCESS_SPEED 0
+/* Swap the values of two variables, without multiple evaluation. */
+#ifndef swap
+# define swap(a, b) ({ typeof(a) _a = (a); (a) = (b); (b) = _a; })
#endif
-#define UNALIGNED_ACCESS_IS_ALLOWED (UNALIGNED_ACCESS_SPEED >= 1)
-#define UNALIGNED_ACCESS_IS_FAST (UNALIGNED_ACCESS_SPEED >= 2)
-#define UNALIGNED_ACCESS_IS_VERY_FAST (UNALIGNED_ACCESS_SPEED >= 3)
+/* (Optional) Efficiently swap the bytes of a 16-bit integer. */
+#if GCC_PREREQ(4, 8) || __has_builtin(__builtin_bswap16)
+# define compiler_bswap16 __builtin_bswap16
+#endif
-#ifndef typeof
-# error "missing required definition of typeof"
+/* (Optional) Efficiently swap the bytes of a 32-bit integer. */
+#if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap32)
+# define compiler_bswap32 __builtin_bswap32
#endif
-#if !defined(min) || !defined(max) || !defined(swap)
-# error "missing required definitions of min(), max(), and swap() macros"
+/* (Optional) Efficiently swap the bytes of a 64-bit integer. */
+#if GCC_PREREQ(4, 3) || __has_builtin(__builtin_bswap64)
+# define compiler_bswap64 __builtin_bswap64
#endif
+/* (Optional) Find Last Set bit and Find First Set bit macros. */
+#define compiler_fls32(n) (31 - __builtin_clz(n))
+#define compiler_fls64(n) (63 - __builtin_clzll(n))
+#define compiler_ffs32(n) __builtin_ctz(n)
+#define compiler_ffs64(n) __builtin_ctzll(n)
+
+/* Optional definitions for checking with 'sparse'. */
#ifdef __CHECKER__
# define _bitwise_attr __attribute__((bitwise))
# define _force_attr __attribute__((force))
# define _force_attr
#endif
-#ifndef BUILD_BUG_ON
-# define BUILD_BUG_ON(expr) ((void)sizeof(char[1 - 2*!!(expr)]))
+/* STATIC_ASSERT() - verify the truth of an expression at compilation time. */
+#if __STDC_VERSION__ >= 201112L
+# define STATIC_ASSERT(expr) _Static_assert((expr), "")
+#else
+# define STATIC_ASSERT(expr) ((void)sizeof(char[1 - 2 * !(expr)]))
#endif
+#define CONCAT_IMPL(s1, s2) s1##s2
+
+/* CONCAT() - concatenate two tokens at preprocessing time. */
+#define CONCAT(s1, s2) CONCAT_IMPL(s1, s2)
+
#endif /* _WIMLIB_COMPILER_H */
git://wimlib.net / wimlib / blobdiff