Add gcc specific optimization for fma

include/ccmath/math/basic/fma.hpp

@@ -8,10 +8,10 @@
 
 #pragma once
 
-#include "ccmath/internal/predef/unlikely.hpp"
+// #include "ccmath/internal/predef/unlikely.hpp"
+#include <type_traits>
 #include "ccmath/math/compare/isinf.hpp"
 #include "ccmath/math/compare/isnan.hpp"
-#include <type_traits>
 
 namespace ccm
 {
@@ -27,6 +27,13 @@ namespace ccm
 	template <typename T, std::enable_if_t<!std::is_integral_v<T>, bool> = true>
 	constexpr T fma(T x, T y, T z) noexcept
 	{
+		// Check for GCC 6.1 or later
+#if defined(__GNUC__) && (__GNUC__ > 6 || (__GNUC__ == 6 && __GNUC_MINOR__ >= 1)) && !defined(__clang__)
+		if constexpr (std::is_same_v<T, float>) { return __builtin_fmaf(x, y, z); }
+		else if constexpr (std::is_same_v<T, double>) { return __builtin_fma(x, y, z); }
+		else if constexpr (std::is_same_v<T, long double>) { return __builtin_fmal(x, y, z); }
+		else { __builtin_fma(x, y, z); }
+#else
 		// Handle infinity
 		if (CCM_UNLIKELY((x == static_cast<T>(0) && ccm::isinf(y)) || (y == T{0} && ccm::isinf(x)))) { return std::numeric_limits<T>::quiet_NaN(); }
 		if (CCM_UNLIKELY(x * y == std::numeric_limits<T>::infinity() && z == -std::numeric_limits<T>::infinity()))
@@ -41,8 +48,9 @@ namespace ccm
 			return std::numeric_limits<T>::quiet_NaN();
 		}
 
-		// We have to hope the compiler optimizes this. Currently there is no builtin fma that works with static_assert.
+		// We have to hope the compiler optimizes this. Currently, there is no builtin fma that works with static_assert.
 		return (x * y) + z;
+#endif
 	}
 
 	template <typename T, std::enable_if_t<std::is_integral_v<T>, bool> = true>