: Adds DSP op for RoPE (#11264)

Summary: Pull Request resolved: #11264

Reviewed By: hsharma35

Differential Revision: D75605145

Author: nitish2112

backends/cadence/aot/ops_registrations.py

@@ -167,6 +167,13 @@
     "where_Scalar.out(Tensor condition, float self, float other, *, Tensor(a!) out) -> Tensor(a!)"
 )
 
+lib.define(
+    "rope(Tensor input, Tensor sin_tensor, Tensor cos_tensor, Tensor? pos) -> (Tensor out)"
+)
+lib.define(
+    "rope.out(Tensor input, Tensor sin_tensor, Tensor cos_tensor, Tensor? pos, *, Tensor(a!) out) -> Tensor(a!)"
+)
+
 # ------------------------------------ #
 #   Migrated from custom_ops.yaml      #
 # ------------------------------------ #
@@ -954,3 +961,28 @@ def where_Scalar_meta(
     other: float,
 ) -> torch.Tensor:
     return condition.new_empty(condition.size(), dtype=torch.float32)
+
+@register_fake("cadence::rope")
+def rope_meta(
+    input: torch.Tensor,
+    sin_tensor: torch.Tensor,
+    cos_tensor: torch.Tensor,
+    pos: Optional[torch.Tensor],
+) -> torch.Tensor:
+    input_shape = list(input.shape)
+    assert (
+        len(input_shape) in (4, 5) and input_shape[0] == 1
+    ), f"input shape {input_shape} must be (1, seq, h, hd) or (1, seq, h, hd / 2, 2)"
+    seq = input_shape[1]
+    h = input_shape[2]
+    hd = prod(input_shape) / (seq * h)
+    sin_shape = list(sin_tensor.shape)
+    cos_shape = list(cos_tensor.shape)
+    assert sin_shape == cos_shape, f"{sin_shape=} must be same as {cos_shape}"
+    assert (
+        len(sin_shape) == 2 and sin_shape[-1] == hd//2
+    ), f"{sin_shape=} must be [seq, hd/2]"
+    assert (
+        pos is None or len(pos.shape) == 1 and pos.shape[0] == seq
+    ), f"{pos.shape} must be [{seq}]"
+    return input.new_empty(input.shape, dtype=input.dtype)