Standalone sweep once softmax kernel w/ ckProfiler (#295)

* use 'sweep once' softmax kernel where applicable

* threadwise copy's dst buffer can specify invalid element value

* add int8 in/out float compute softmax support

give a bit of leeway for int absolute tolerance as there's a single data point of all test cases showing off-by-1 error

* format

* softmax inherits DeviceNormalization

* softmax profiler stub

* tighten up reference softmax interface

* example prints tensor dimension

* add fp32 to softmax profiler

* rename header

* hook with ckProfiler

* format

* resolve merge conflict

* resolve merge conflicts

* update normalization profiler help string

* resolve conflict

* typo

* remove residual

* softmax profiler: address feedback

* test for mixed precision input/output

* fully qualify ck::math::isnan

* add comment for device normalization interface

* revise wording

* constness for alpha/beta scaler pointer

include/ck/tensor_operation/gpu/thread/threadwise_tensor_slice_transfer.hpp

@@ -236,9 +236,14 @@ template <typename SrcData,
           index_t SrcScalarPerVector,
           index_t SrcScalarStrideInVector,
           bool SrcResetCoordinateAfterRun,
+          bool InvalidElementAsNaN                                        = false,
           typename enable_if<DstDesc::IsKnownAtCompileTime(), bool>::type = false>
 struct ThreadwiseTensorSliceTransfer_v2
 {
+    static_assert((InvalidElementAsNaN && !std::is_integral<DstData>::value) ||
+                      (!InvalidElementAsNaN),
+                  "Filling invalid element as NaN is only for floating point types");
+
     static constexpr index_t nDim = SliceLengths::Size();
 
     using Index = MultiIndex<nDim>;
@@ -318,8 +323,18 @@ struct ThreadwiseTensorSliceTransfer_v2
                     dst_desc.CalculateOffset(to_multi_index(dst_slice_origin_idx) + src_data_idx +
                                              i * src_scalar_step_in_vector);
 
-                dst_buf(Number<dst_offset>{}) =
-                    type_convert<DstData>(src_vector.template AsType<SrcData>()[i]);
+                if constexpr(InvalidElementAsNaN)
+                {
+                    dst_buf(Number<dst_offset>{}) =
+                        is_src_valid
+                            ? type_convert<DstData>(src_vector.template AsType<SrcData>()[i])
+                            : NumericLimits<DstData>::QuietNaN();
+                }
+                else
+                {
+                    dst_buf(Number<dst_offset>{}) =
+                        type_convert<DstData>(src_vector.template AsType<SrcData>()[i]);
+                }
             });
 
             if constexpr(idx_1d.value != num_access - 1)