Remove undefined behavior from default constructor of PredicatedTileA…

…ccessIteratorParams. (NVIDIA#1258)

Currently, the default constructor of
`PredicatedTileAccessIteratorParams` will invoke undefined behavior in
its invocation of the `initialize` function. Specifically, it will
attempt to read from the uninitialized variables
`desc.element_size_bits` and `desc.advance_rank`. This commit changes
the default constructors of both `*Params` and `*Desc` to
zero-initialize all uninitialized members.

include/cutlass/transform/threadblock/predicated_tile_access_iterator_params.h

@@ -46,6 +46,7 @@
 
 #include "cutlass/cutlass.h"
 #include "cutlass/array.h"
+#include "cutlass/detail/helper_macros.hpp"
 #include "cutlass/layout/matrix.h"
 #include "cutlass/layout/pitch_linear.h"
 
@@ -60,8 +61,8 @@ namespace threadblock {
 /// Predicated tile access iterator descriptor object containing template dependent state
 struct PredicatedTileAccessIteratorDesc {
 
-  int element_size_bits;
-  int advance_rank;
+  int element_size_bits = -1;
+  int advance_rank = -1;
   layout::PitchLinearCoord threadblock_shape;
   layout::PitchLinearCoord threadmap_iterations;
   layout::PitchLinearCoord threadmap_delta;
@@ -71,7 +72,7 @@ struct PredicatedTileAccessIteratorDesc {
   //
 
   CUTLASS_HOST_DEVICE
-  PredicatedTileAccessIteratorDesc() { }
+  PredicatedTileAccessIteratorDesc() = default;
 
   CUTLASS_HOST_DEVICE
   PredicatedTileAccessIteratorDesc(
@@ -232,23 +233,25 @@ struct PredicatedTileAccessIteratorParams {
   // Data members
   //
   /// stride of pitch-linear layout (units of Element)
-  LongIndex stride_;
+  LongIndex stride_ = 0;
   /// amount (in byte) to increment pointer to move to next access along
   /// strided dimension
-  LongIndex inc_strided_;
+  LongIndex inc_strided_ = 0;
   /// amount (in byte) to increment pointer from last access to first access
   /// of next tile
-  LongIndex inc_next_;
+  LongIndex inc_next_ = 0;
   /// amount (in byte) to increment pointer from first access of current tile
   /// to first access of next tile
-  LongIndex inc_advance_;
+  LongIndex inc_advance_ = 0;
 
   //
   // Methods
   //
 
   CUTLASS_HOST_DEVICE
   Status initialize(LongIndex stride, PredicatedTileAccessIteratorDesc desc) {
+    CUTLASS_ASSERT(desc.element_size_bits > 0);
+    CUTLASS_ASSERT(desc.advance_rank == 0 || desc.advance_rank == 1);
 
     stride_ = stride;
 
@@ -277,9 +280,7 @@ struct PredicatedTileAccessIteratorParams {
   }
 
   CUTLASS_HOST_DEVICE
-  PredicatedTileAccessIteratorParams() {
-    initialize(LongIndex(0), PredicatedTileAccessIteratorDesc());
-  }
+  PredicatedTileAccessIteratorParams() = default;
 
   CUTLASS_HOST_DEVICE
   PredicatedTileAccessIteratorParams(Index stride, PredicatedTileAccessIteratorDesc desc) {