Extend utilities for checking a scalar value (#2587)

Extend the `is_singleton_value` utility to check for singleton values
that may be either 0D or 1D tensors.

---------

Signed-off-by: Ganesan Ramalingam <grama@microsoft.com>

Author: gramalingam

onnxscript/rewriter/_ir_utils.py

@@ -78,23 +78,34 @@ def get_numpy_value(val: ir.Value | None) -> np.ndarray | None:
     return None
 
 
-def get_singleton_value(val: ir.Value | None, rank: int | None = None):
+def get_singleton_value(val: ir.Value | None, rank: int | Sequence[int] | None = None):
     """Returns element of a single element tensor constant value, and None otherwise.
 
-    If rank is specified, it checks that the value has the given rank.
+    If an int rank is specified, it checks that the value has the given rank.
+    If the rank is a sequence of ints, it checks that the value has one of the given ranks.
+
+    Thus, `rank=0` checks for a scalar, `rank=1` checks for a 1D tensor, and
+    `rank=(0,1)` checks for either a scalar or a 1D tensor.
     """
     np_val = get_numpy_value(val)
     if np_val is not None and np_val.size == 1:
-        if rank is None or (np_val.ndim == rank):
-            return np_val.item()
+        value = np_val.item()
+        if (rank is None) or (isinstance(rank, int) and (np_val.ndim == rank)):
+            return value
+        if isinstance(rank, Sequence) and (np_val.ndim in rank):
+            return value
     return None
 
 
 def is_singleton_value(
-    val: ir.Value | None, expected: float | int | Callable, *, rtol: float | None = None
+    val: ir.Value | None,
+    expected: float | int | Callable,
+    *,
+    rtol: float | None = None,
+    rank: int | Sequence[int] | None = None,
 ) -> bool:
     """Returns True if the value is a single element tensor with given value, and False otherwise."""
-    scalar = get_singleton_value(val)
+    scalar = get_singleton_value(val, rank=rank)
     if scalar is None:
         return False
     if callable(expected):

onnxscript/rewriter/rules/fusion/_rotary_embedding.py

@@ -43,19 +43,9 @@ def pattern(self, op, x, freqs, start1, end1, start2, end2, one1, one2):
     def check(self, op, x, start1, end1, start2, end2, one1, one2, **_) -> pattern.MatchResult:  # type: ignore[name-defined]
         check_result = pattern.MatchResult()
 
-        def is_one(val):
-            """Check if val is a 0/1 dimensional tensor with a single element equal to 1."""
-            np_val = _ir_utils.get_numpy_value(val)
-            return (
-                np_val is not None
-                and np_val.size == 1
-                and np_val.ndim <= 1
-                and np_val.item() == 1
-            )
-
-        if not is_one(one1):
+        if not _ir_utils.is_singleton_value(one1, 1):
             return check_result.fail("Unsqueeze axes is not [1]", one1)
-        if not is_one(one2):
+        if not _ir_utils.is_singleton_value(one2, 1):
             return check_result.fail("Unsqueeze axes is not [1]", one2)
 
         # x needs to be a 4D tensor with known last dimension size (== head_size) and known second dimension (num_heads)