Add SoftMax and GELU activation functions to DMLX (#573)

Libraries/DirectMLX.h

@@ -959,6 +959,13 @@ namespace dml
         {
             return FusedActivation(DML_OPERATOR_ACTIVATION_CELU, alpha);
         }
+
+#if DML_TARGET_VERSION >= 0x5100
+        static FusedActivation Gelu()
+        {
+            return FusedActivation(DML_OPERATOR_ACTIVATION_GELU);
+        }
+#endif // DML_TARGET_VERSION >= 0x5100
     };
 
     // Implementation detail helper for determining if a list of expressions share the same GraphBuilder.
@@ -1855,6 +1862,18 @@ namespace dml
         DMLX_ACTIVATION_IMPL(ACTIVATION_SOFTMAX);
     }
 
+#if DML_TARGET_VERSION >= 0x5100
+    inline Expression ActivationSoftmax(Expression input, Span<const uint32_t> axes)
+    {
+        DMLX_ACTIVATION_IMPL_2(ACTIVATION_SOFTMAX1, AxisCount, static_cast<uint32_t>(axes.size()), Axes, axes.data());
+    }
+
+    inline Expression ActivationGelu(Expression input)
+    {
+        DMLX_ACTIVATION_IMPL(ACTIVATION_GELU);
+    }
+#endif
+
     inline Expression ActivationSoftplus(Expression input, float steepness = 1.0f)
     {
         DMLX_ACTIVATION_IMPL_1(ACTIVATION_SOFTPLUS, Steepness, steepness);