fix: Repair aten.where with Numpy + Broadcast

- Improve individual broadcasting logic for each of the three input
tensors
- Remove unnecessary pre-broadcasting step
- Update function typing documentation accordingly
- Add regression test case to catch similar behavior

Author: gs-olive

py/torch_tensorrt/dynamo/conversion/impl/condition/ops.py

@@ -11,7 +11,7 @@
     get_trt_tensor,
 )
 from torch_tensorrt.dynamo.conversion.impl.slice import expand
-from torch_tensorrt.fx.converters.converter_utils import broadcast, set_layer_name
+from torch_tensorrt.fx.converters.converter_utils import set_layer_name
 from torch_tensorrt.fx.types import TRTTensor
 
 
@@ -27,16 +27,6 @@ def where(
     if not (broadcastable(input, other)):
         assert "The two torch tensors should be broadcastable"
 
-    # get output shape
-    # purpose of this is to bring input and other rank same as
-    # output_shape to input it to the add_expand operation
-    # condition will have dimension of either input or other
-    input, other = broadcast(ctx.net, input, other, f"{name}_x", f"{name}_y")
-    if len(tuple(condition.shape)) != len(tuple(input.shape)):
-        condition, input = broadcast(
-            ctx.net, condition, input, f"{name}_condition", f"{name}_x"
-        )
-
     x_shape = list(input.shape)
     y_shape = list(other.shape)
     condition_shape = list(condition.shape)
@@ -71,7 +61,11 @@ def where(
                     if isinstance(input, torch.Tensor)
                     else np.expand_dims(input, axis=0)
                 )
-            input = input.expand(output_shape)
+            input = (
+                input.expand(output_shape)
+                if isinstance(input, torch.Tensor)
+                else np.broadcast_to(input, output_shape)
+            )
         x_val = get_trt_tensor(ctx, input, f"{name}_x")
     else:
         x_val = input
@@ -89,7 +83,11 @@ def where(
                     if isinstance(other, torch.Tensor)
                     else np.expand_dims(other, axis=0)
                 )
-            other = other.expand(output_shape)
+            other = (
+                other.expand(output_shape)
+                if isinstance(other, torch.Tensor)
+                else np.broadcast_to(other, output_shape)
+            )
         y_val = get_trt_tensor(ctx, other, f"{name}_y")
     else:
         y_val = other

tests/py/dynamo/conversion/test_where_aten.py

@@ -59,6 +59,23 @@ def forward(self, condition):
             (condition,),
         )
 
+    def test_const_input_with_broadcast(self):
+        class Where(nn.Module):
+            def __init__(self, *args, **kwargs) -> None:
+                super().__init__(*args, **kwargs)
+                self.inputY = torch.randn((1,))
+                self.inputX = torch.randn((1,))
+
+            def forward(self, condition):
+                return torch.ops.aten.where.self(condition, self.inputX, self.inputY)
+
+        input1 = torch.randn((5, 6, 7))
+        condition = input1 < 0
+        self.run_test(
+            Where(),
+            (condition,),
+        )
+
 
 if __name__ == "__main__":
     run_tests()