Add error messages for int64 non-available ops (#80)

* Add error messages for int64 non-available ops

* Move warning to common code

Author: abhudev

aten/src/ATen/native/mps/operations/Activation.mm

@@ -416,6 +416,7 @@ Tensor relu_mps(const Tensor& self) {
   using namespace mps;
   using CachedGraph = MPSUnaryCachedGraph;
   TORCH_CHECK(output.is_mps());
+  TORCH_CHECK(self.scalar_type() != ScalarType::Long, "MPS does not support sigmoid op with int64 input")
 
   if(output.numel() == 0) {
     return;

aten/src/ATen/native/mps/operations/UnaryOps.mm

@@ -195,6 +195,7 @@ void unary_op(const Tensor& self, const Tensor& output, std::string op_name, Una
 
 TORCH_IMPL_FUNC(log1p_out_mps) (const Tensor& self, const Tensor& output)
 {
+    TORCH_CHECK(self.scalar_type() != ScalarType::Long, "MPS does not support log1p op with int64 input")
     using namespace mps;
     if (!output.is_same_size(self)) {
       output.resize_(self.sizes());