BAN/LibC: Implement remainder

This is basically just fmod but with fprem1 instead of fprem

BAN/include/BAN/Math.h

@@ -172,7 +172,23 @@ namespace BAN::Math
 			"jne 1b;"
 			: "+t"(a)
 			: "u"(b)
-			: "ax"
+			: "ax", "cc"
+		);
+		return a;
+	}
+
+	template<floating_point T>
+	inline constexpr T remainder(T a, T b)
+	{
+		asm(
+			"1:"
+			"fprem1;"
+			"fnstsw %%ax;"
+			"testb $4, %%ah;"
+			"jne 1b;"
+			: "+t"(a)
+			: "u"(b)
+			: "ax", "cc"
 		);
 		return a;
 	}

userspace/libraries/LibC/math.cpp

@@ -256,7 +256,7 @@ FUNC_EXPR1(nearbyint, BAN::Math::rint(a))
 FUNC_EXPR2(nextafter, nextafter_impl(a, b))
 FUNC_EXPR2_TYPE(nexttoward, long double, nextafter_impl(a, b))
 FUNC_EXPR2(pow, ({ if (isnan(a)) return a; if (isnan(b)) return b; BAN::Math::pow(a, b); }))
-// remainder
+BAN_FUNC2(remainder)
 // remquo
 BAN_FUNC1(rint)
 FUNC_EXPR1(round, ({ if (!isfinite(a)) return a; BAN::Math::round(a); }))