reverted changes (#46254)

paddle/fluid/operators/mkldnn/concat_mkldnn_op.cc

@@ -77,25 +77,8 @@ class ConcatMKLDNNHandler
     }
 
     auto dst_dims = phi::vectorize<int64_t>(output->dims());
-
-    dnnl::memory::desc dst_md;
-
-    // if concat is being used as a stack op(all source memories dims on
-    // concat_axis are equal to 1), then it may choose a non-optimal memory
-    // format tag for destination, because concat primitive is chosing it based
-    // on source memory descriptors and f.e.200x1x10 can be described as both
-    // abc and bac and both would be using exact same physical layout, but in
-    // that scenario bac will be chosen for destination no matter which
-    // formats are being set in inputs. In that scenario we are enforcing using
-    // a dense format, because it is the most common one and should be the best
-    // in terms of the performance
-    const auto src0_tz = srcs_md[0].dims();
-    if (std::find(src0_tz.begin(), src0_tz.end(), 1) != src0_tz.end()) {
-      dst_md = memory::desc(
-          dst_dims, dt, platform::GetPlainMKLDNNFormat(dst_dims.size()));
-    } else {
-      dst_md = memory::desc(dst_dims, dt, MKLDNNMemoryFormat::any);
-    }
+    dnnl::memory::desc dst_md =
+        memory::desc(dst_dims, dt, MKLDNNMemoryFormat::any);
 
     this->AcquireForwardPrimitiveDescriptor(dst_md, concat_axis, srcs_md);
   }