common/Compiler: reorganize code

- split compiler builtins and code that can be considered as architeture intrinsics - group compiler-specific code
DaemonEngine · May 16, 2024 · 6bcac3e · 6bcac3e
1 parent 8c642f1
commit 6bcac3e
Showing 1 changed file with 69 additions and 59 deletions.
diff --git a/src/common/Compiler.h b/src/common/Compiler.h
@@ -33,14 +33,49 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef COMMON_COMPILER_H_
 #define COMMON_COMPILER_H_
 
+// Code making use of compiler builtins which can be considered as architecture intrinsics.
+
 // CountTrailingZeroes returns the number of trailing zeroes of the argument in binary.
 // The result is unspecified if the input is 0.
 int CountTrailingZeroes(unsigned int x);
 int CountTrailingZeroes(unsigned long x);
 int CountTrailingZeroes(unsigned long long x);
 
+#if defined( __GNUC__ )
+	inline int CountTrailingZeroes(unsigned int x)
+		{ return __builtin_ctz(x); }
+	inline int CountTrailingZeroes(unsigned long x)
+		{ return __builtin_ctzl(x); }
+	inline int CountTrailingZeroes(unsigned long long x)
+		{ return __builtin_ctzll(x); }
+#elif defined( _MSC_VER )
+	inline int CountTrailingZeroes(unsigned int x)
+		{ unsigned long ans; _BitScanForward(&ans, x); return ans; }
+	inline int CountTrailingZeroes(unsigned long x)
+		{ unsigned long ans; _BitScanForward(&ans, x); return ans; }
+	#ifdef _WIN64
+	inline int CountTrailingZeroes(unsigned long long x)
+		{ unsigned long ans; _BitScanForward64(&ans, x); return ans; }
+	#else
+	inline int CountTrailingZeroes(unsigned long long x)
+	{
+		unsigned long ans;
+		bool nonzero =  _BitScanForward(&ans, static_cast<unsigned long>(x));
+		if (!nonzero) { _BitScanForward(&ans, x >> 32); }
+		return ans;
+	}
+	#endif
+#else
+	inline int CountTrailingZeroes(unsigned int x)
+		{ int i = 0; while (i < 32 && !(x & 1)) { ++i; x >>= 1; } return i; }
+	inline int CountTrailingZeroes(unsigned long x)
+		{ int i = 0; while (i < 64 && !(x & 1)) { ++i; x >>= 1; } return i; }
+	inline int CountTrailingZeroes(unsigned long long x)
+		{ int i = 0; while (i < 64 && !(x & 1)) { ++i; x >>= 1; } return i; }
+#endif
+
 // GCC and Clang
-#ifdef __GNUC__
+#if defined( __GNUC__ )
 
 // Emit a nice warning when a function is used
 #define DEPRECATED __attribute__((__deprecated__))
@@ -94,6 +129,19 @@ int CountTrailingZeroes(unsigned long long x);
 	#define BREAKPOINT()
 #endif
 
+/* Compiler can be fooled when calling ASSERT_UNREACHABLE() macro at end of non-void function.
+In this case, compiler is complaining because control reaches end of non-void function,
+even if the execution flow is expected to be taken down by assert before.
+
+That's why we use these compiler specific unreachable builtin on modern compilers,
+ASSERT_UNREACHABLE() macro makes use of this UNREACHABLE() macro, preventing useless warnings.
+Unsupported compilers will raise "control reaches end of non-void function" warnings but
+that's not a big issue and that's likely to never happen (these compilers would be too old and
+would lack too much features to compile Daemon anyway).
+
+See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0627r0.pdf */
+#define UNREACHABLE() __builtin_unreachable()
+
 #if defined(__SANITIZE_ADDRESS__) // Detects GCC and MSVC AddressSanitizer
 #   define USING_ADDRESS_SANITIZER
 #   define USING_SANITIZER
@@ -119,9 +167,14 @@ int CountTrailingZeroes(unsigned long long x);
 #   define ATTRIBUTE_NO_SANITIZE_ADDRESS
 #endif
 
-inline int CountTrailingZeroes(unsigned int x) { return __builtin_ctz(x); }
-inline int CountTrailingZeroes(unsigned long x) { return __builtin_ctzl(x); }
-inline int CountTrailingZeroes(unsigned long long x) { return __builtin_ctzll(x); }
+// The new -Wimplicit-fallthrough warning...
+#if defined(__clang__) && __clang_major__ >= 6
+#   define DAEMON_FALLTHROUGH [[clang::fallthrough]]
+#elif __GNUC__ >= 7
+#   define DAEMON_FALLTHROUGH [[gnu::fallthrough]]
+#else
+#   define DAEMON_FALLTHROUGH
+#endif
 
 // Microsoft Visual C++
 #elif defined( _MSC_VER )
@@ -162,23 +215,9 @@ inline int CountTrailingZeroes(unsigned long long x) { return __builtin_ctzll(x)
 #define DLLEXPORT __declspec(dllexport)
 #define DLLIMPORT __declspec(dllimport)
 #define BREAKPOINT() __debugbreak()
+#define UNREACHABLE() __assume(0)
 #define ATTRIBUTE_NO_SANITIZE_ADDRESS
-
-inline int CountTrailingZeroes(unsigned int x) { unsigned long ans; _BitScanForward(&ans, x); return ans; }
-inline int CountTrailingZeroes(unsigned long x) { unsigned long ans; _BitScanForward(&ans, x); return ans; }
-#ifdef _WIN64
-inline int CountTrailingZeroes(unsigned long long x) { unsigned long ans; _BitScanForward64(&ans, x); return ans; }
-#else
-inline int CountTrailingZeroes(unsigned long long x)
-{
-    unsigned long ans;
-    bool nonzero =  _BitScanForward(&ans, static_cast<unsigned long>(x));
-    if (!nonzero) {
-        _BitScanForward(&ans, x >> 32);
-    }
-    return ans;
-}
-#endif
+#define DAEMON_FALLTHROUGH
 
 // Other compilers, unsupported
 #else
@@ -196,21 +235,12 @@ inline int CountTrailingZeroes(unsigned long long x)
 #define DLLEXPORT
 #define DLLIMPORT
 #define BREAKPOINT()
-
+#define UNREACHABLE()
 #define ATTRIBUTE_NO_SANITIZE_ADDRESS
-
-inline int CountTrailingZeroes(unsigned int x) { int i = 0; while (i < 32 && !(x & 1)) { ++i; x >>= 1; } return i; }
-inline int CountTrailingZeroes(unsigned long x) { int i = 0; while (i < 64 && !(x & 1)) { ++i; x >>= 1; } return i; }
-inline int CountTrailingZeroes(unsigned long long x) { int i = 0; while (i < 64 && !(x & 1)) { ++i; x >>= 1; } return i; }
+#define DAEMON_FALLTHROUGH
 #endif
 
-#if defined(__MINGW32__) && defined(__i386__)
-// On x86, GCC expects 16-byte stack alignment (used for SSE instructions), but MSVC only uses 4-byte alignment.
-// Therefore the stack needs to be adjusted whenever MSVC code calls into GCC code.
-#   define ALIGN_STACK_FOR_MINGW __attribute__((force_align_arg_pointer))
-#else
-#   define ALIGN_STACK_FOR_MINGW
-#endif
+// Keywords specific to C++ versions
 
 // noexcept keyword, this should be used on all move constructors and move
 // assignments so that containers move objects instead of copying them.
@@ -248,36 +278,16 @@ inline int CountTrailingZeroes(unsigned long long x) { int i = 0; while (i < 64
 #   define CONSTEXPR_FUNCTION_RELAXED
 #endif
 
-// The new -Wimplicit-fallthrough warning...
-#if defined(__clang__) && __clang_major__ >= 6
-#   define DAEMON_FALLTHROUGH [[clang::fallthrough]]
-#elif __GNUC__ >= 7
-#   define DAEMON_FALLTHROUGH [[gnu::fallthrough]]
+// Compiler specificities we can't disable.
+
+#if defined(__MINGW32__) && defined(__i386__)
+// On x86, GCC expects 16-byte stack alignment (used for SSE instructions), but MSVC only uses 4-byte alignment.
+// Therefore the stack needs to be adjusted whenever MSVC code calls into GCC code.
+#   define ALIGN_STACK_FOR_MINGW __attribute__((force_align_arg_pointer))
 #else
-#   define DAEMON_FALLTHROUGH
+#   define ALIGN_STACK_FOR_MINGW
 #endif
 
-/* Compiler can be fooled when calling ASSERT_UNREACHABLE() macro at end of non-void function.
- * In this case, compiler is complaining because control reaches end of non-void function,
- * even if the execution flow is expected to be taken down by assert before.
- *
- * That's why we use these compiler specific unreachable builtin on modern compilers,
- * ASSERT_UNREACHABLE() macro makes use of this UNREACHABLE() macro, preventing useless warnings.
- * Unsupported compilers will raise "control reaches end of non-void function" warnings but
- * that's not a big issue and that's likely to never happen (these compilers would be too old and
- * would lack too much features to compile Daemon anyway).
- *
- * See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0627r0.pdf
-*/
-#if defined(_MSC_VER) //UNREACHABLE
-	#define UNREACHABLE() __assume(0)
-// All of gcc, clang and icc define __GNUC__
-#elif defined(__GNUC__)
-	#define UNREACHABLE() __builtin_unreachable()
-#else // UNREACHABLE
-	#define UNREACHABLE()
-#endif // UNREACHABLE
-
 /* Use a C++11 braced initializer on MSVC instead of a bracket initializer
 when zeroing a struct. This works around a bug in how MSVC generates implicit
 default constructors. -- Amanieu