Cleanup on the new Math APIs (dotnet/coreclr#20993)

* Updating the cached HAVE_COMPATIBLE_ILOGB0_EXITCODE and HAVE_COMPATIBLE_ILOGBNAN_EXITCODE to 1

* Fixing MaxMagnitude and MinMagnitude to correctly handle the case when ax and ay are equal

Signed-off-by: dotnet-bot <dotnet-bot@microsoft.com>

Author: tannergooding

src/System.Private.CoreLib/shared/System/Math.cs

@@ -658,15 +658,18 @@ public static double MaxMagnitude(double x, double y)
             }
 
             // We do this comparison first and separately to handle the -0.0 to +0.0 comparision
-            // * Doing (x < y) first could get transformed into (y >= x) by the JIT which would
+            // * Doing (ax < ay) first could get transformed into (ay >= ax) by the JIT which would
             //   then return an incorrect value
 
-            if (x == y)
+            double ax = Abs(x);
+            double ay = Abs(y);
+
+            if (ax == ay)
             {
                 return double.IsNegative(x) ? y : x;
             }
 
-            return (Abs(x) < Abs(y)) ? y : x;
+            return (ax < ay) ? y : x;
         }
 
         [NonVersionable]
@@ -803,15 +806,18 @@ public static double MinMagnitude(double x, double y)
             }
 
             // We do this comparison first and separately to handle the -0.0 to +0.0 comparision
-            // * Doing (x < y) first could get transformed into (y >= x) by the JIT which would
+            // * Doing (ax < ay) first could get transformed into (ay >= ax) by the JIT which would
             //   then return an incorrect value
 
-            if (x == y)
+            double ax = Abs(x);
+            double ay = Abs(y);
+
+            if (ax == ay)
             {
                 return double.IsNegative(x) ? x : y;
             }
 
-            return (Abs(x) < Abs(y)) ? x : y;
+            return (ax < ay) ? x : y;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]

src/System.Private.CoreLib/shared/System/MathF.cs

@@ -206,15 +206,18 @@ public static float MaxMagnitude(float x, float y)
             }
 
             // We do this comparison first and separately to handle the -0.0 to +0.0 comparision
-            // * Doing (x < y) first could get transformed into (y >= x) by the JIT which would
+            // * Doing (ax < ay) first could get transformed into (ay >= ax) by the JIT which would
             //   then return an incorrect value
 
-            if (x == y)
+            float ax = Abs(x);
+            float ay = Abs(y);
+
+            if (ax == ay)
             {
                 return float.IsNegative(x) ? y : x;
             }
 
-            return (Abs(x) < Abs(y)) ? y : x;
+            return (ax < ay) ? y : x;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -241,15 +244,18 @@ public static float MinMagnitude(float x, float y)
             }
 
             // We do this comparison first and separately to handle the -0.0 to +0.0 comparision
-            // * Doing (x < y) first could get transformed into (y >= x) by the JIT which would
+            // * Doing (ax < ay) first could get transformed into (ay >= ax) by the JIT which would
             //   then return an incorrect value
 
-            if (x == y)
+            float ax = Abs(x);
+            float ay = Abs(y);
+
+            if (ax == ay)
             {
                 return float.IsNegative(x) ? x : y;
             }
 
-            return (Abs(x) < Abs(y)) ? x : y;
+            return (ax < ay) ? x : y;
         }
 
         [Intrinsic]