Switch text encoder to manual cast.

Use fp16 text encoder weights for CPU inference to lower memory usage.

comfy/ops.py

@@ -29,6 +29,39 @@ def conv_nd(dims, *args, **kwargs):
     else:
         raise ValueError(f"unsupported dimensions: {dims}")
 
+def cast_bias_weight(s, input):
+    bias = None
+    if s.bias is not None:
+        bias = s.bias.to(device=input.device, dtype=input.dtype)
+    weight = s.weight.to(device=input.device, dtype=input.dtype)
+    return weight, bias
+
+class manual_cast:
+    class Linear(Linear):
+        def forward(self, input):
+            weight, bias = cast_bias_weight(self, input)
+            return torch.nn.functional.linear(input, weight, bias)
+
+    class Conv2d(Conv2d):
+        def forward(self, input):
+            weight, bias = cast_bias_weight(self, input)
+            return self._conv_forward(input, weight, bias)
+
+    class Conv3d(Conv3d):
+        def forward(self, input):
+            weight, bias = cast_bias_weight(self, input)
+            return self._conv_forward(input, weight, bias)
+
+    class GroupNorm(GroupNorm):
+        def forward(self, input):
+            weight, bias = cast_bias_weight(self, input)
+            return torch.nn.functional.group_norm(input, self.num_groups, weight, bias, self.eps)
+
+    class LayerNorm(LayerNorm):
+        def forward(self, input):
+            weight, bias = cast_bias_weight(self, input)
+            return torch.nn.functional.layer_norm(input, self.normalized_shape, weight, bias, self.eps)
+
 @contextmanager
 def use_comfy_ops(device=None, dtype=None): # Kind of an ugly hack but I can't think of a better way
     old_torch_nn_linear = torch.nn.Linear