Support whole-number float exponents in ReplacePowWithMulPass (#18851)

Summary:
Pull Request resolved: #18851

Extend `ReplacePowWithMulPass` to accept float exponents that are whole numbers
(e.g., 2.0, 3.0, 4.0) in addition to integer exponents. Previously the pass only
matched `int` typed exponents, causing it to miss valid optimization opportunities
when the exponent was a float with no fractional part.

Changes:
- Broaden the type check from `isinstance(_, int)` to `isinstance(_, (int, float))`
- Add a guard to reject non-whole-number floats (e.g., 1.5, 0.5)
- Convert validated float exponents to `int` before proceeding
- Update docstring to document the new behavior

Reviewed By: hsharma35, mcremon-meta

Differential Revision: D100695654

Author: Hamidreza Khazaei

backends/cadence/aot/replace_ops.py

@@ -2266,19 +2266,25 @@ def _get_split_sizes(self, node: torch.fx.Node) -> Optional[list[tuple[int, ...]
 class ReplacePowWithMulPass(RemoveOrReplacePassInterface):
     """
     Replace the pow op with successive mul ops when the exponent is an
-    integer between 2 and 4 (inclusive).
+    integer between 2 and 4 (inclusive). Float exponents that are whole
+    numbers (e.g., 2.0, 3.0, 4.0) are also accepted.
     """
 
     @property
     def targets(self) -> list[EdgeOpOverload]:
         return [exir_ops.edge.aten.pow.Tensor_Scalar]
 
     def maybe_remove_or_replace(self, node: torch.fx.Node) -> bool:
-        # Check if we have at least 2 args and the exponent is an int
-        if len(node.args) < 2 or not isinstance(node.args[1], int):
+        # Check if we have at least 2 args and the exponent is an int or float
+        if len(node.args) < 2 or not isinstance(node.args[1], (int, float)):
             return False
 
-        exponent = cast(int, node.args[1])
+        exponent_val = node.args[1]
+        if isinstance(exponent_val, float):
+            if not exponent_val.is_integer():
+                return False
+            exponent_val = int(exponent_val)
+        exponent = cast(int, exponent_val)
 
         # Only replace if exponent is between 2 and 4 (inclusive)
         if exponent < 2 or exponent > 4:

backends/cadence/aot/tests/test_replace_ops_passes.py

@@ -1926,8 +1926,8 @@ def test_replace_split_with_sizes_with_slice(self) -> None:
             2,
         )
 
-    @expand([[2], [3], [4]])
-    def test_replace_pow_with_mul(self, exponent: int) -> None:
+    @expand([[2], [3], [4], [2.0], [3.0], [4.0]])
+    def test_replace_pow_with_mul(self, exponent: int | float) -> None:
         x_input = torch.randn(2, 1, 64)
         x = x_input
         original_gm = single_op_builder(
@@ -1956,13 +1956,15 @@ def test_replace_pow_with_mul(self, exponent: int) -> None:
                 graph_after_passes,
                 exir_ops.edge.aten.mul.Tensor,
             ),
-            exponent - 1,
+            int(exponent) - 1,
         )
 
     @expand(
         [
             [1],
             [1.5],
+            [5.0],
+            [0.5],
         ]
     )
     def test_replace_pow_with_mul_not_applied(self, exponent: float) -> None: