PERF: Avoid np.divmod in maybe_sequence_to_range

pandas/_libs/lib.pyi

@@ -231,3 +231,7 @@ def is_range_indexer(
     left: np.ndarray,
     n: int,  # np.ndarray[np.int64, ndim=1]
 ) -> bool: ...
+def is_range(
+    sequence: np.ndarray,
+    diff: int,  # np.ndarray[np.int64, ndim=1]
+) -> bool: ...

pandas/_libs/lib.pyx

@@ -678,6 +678,26 @@ def is_range_indexer(ndarray[int6432_t, ndim=1] left, Py_ssize_t n) -> bool:
     return True
 
 
+@cython.wraparound(False)
+@cython.boundscheck(False)
+def is_range(ndarray[int6432_t, ndim=1] sequence, int64_t diff) -> bool:
+    """
+    Check if sequence is equivalent to a range with the specified diff.
+    """
+    cdef:
+        Py_ssize_t i, n = len(sequence)
+
+    if diff == 0:
+        return False
+
+    for i in range(n):
+
+        if sequence[i] != sequence[0] + i * diff:
+            return False
+
+    return True
+
+
 ctypedef fused ndarr_object:
     ndarray[object, ndim=1]
     ndarray[object, ndim=2]

pandas/core/indexes/range.py

@@ -476,14 +476,9 @@ def _shallow_copy(self, values, name: Hashable = no_default):
             # GH 46675 & 43885: If values is equally spaced, return a
             # more memory-compact RangeIndex instead of Index with 64-bit dtype
             diff = values[1] - values[0]
-            if not missing.isna(diff) and diff != 0:
-                maybe_range_indexer, remainder = np.divmod(values - values[0], diff)
-                if (
-                    lib.is_range_indexer(maybe_range_indexer, len(maybe_range_indexer))
-                    and not remainder.any()
-                ):
-                    new_range = range(values[0], values[-1] + diff, diff)
-                    return type(self)._simple_new(new_range, name=name)
+            if not missing.isna(diff) and lib.is_range(values, diff):
+                new_range = range(values[0], values[-1] + diff, diff)
+                return type(self)._simple_new(new_range, name=name)
         return self._constructor._simple_new(values, name=name)
 
     def _view(self) -> Self: