Make binary bin search reusable. (#6058)

* Move binary search row to hist util.
* Remove dead code.

src/data/ellpack_page.cuh

@@ -13,34 +13,6 @@
 #include <thrust/binary_search.h>
 
 namespace xgboost {
-
-// Find a gidx value for a given feature otherwise return -1 if not found
-__forceinline__ __device__ int BinarySearchRow(
-    bst_uint begin, bst_uint end,
-    common::CompressedIterator<uint32_t> data,
-    int const fidx_begin, int const fidx_end) {
-  bst_uint previous_middle = UINT32_MAX;
-  while (end != begin) {
-    auto middle = begin + (end - begin) / 2;
-    if (middle == previous_middle) {
-      break;
-    }
-    previous_middle = middle;
-
-    auto gidx = data[middle];
-
-    if (gidx >= fidx_begin && gidx < fidx_end) {
-      return gidx;
-    } else if (gidx < fidx_begin) {
-      begin = middle;
-    } else {
-      end = middle;
-    }
-  }
-  // Value is missing
-  return -1;
-}
-
 /** \brief Struct for accessing and manipulating an ellpack matrix on the
  * device. Does not own underlying memory and may be trivially copied into
  * kernels.*/
@@ -83,11 +55,11 @@ struct EllpackDeviceAccessor {
     if (is_dense) {
       gidx = gidx_iter[row_begin + fidx];
     } else {
-      gidx = BinarySearchRow(row_begin,
-                             row_end,
-                             gidx_iter,
-                             feature_segments[fidx],
-                             feature_segments[fidx + 1]);
+      gidx = common::BinarySearchBin(row_begin,
+                                     row_end,
+                                     gidx_iter,
+                                     feature_segments[fidx],
+                                     feature_segments[fidx + 1]);
     }
     return gidx;
   }