ID 417390 - Render time is increased when using an item shader inside of a material mask.

Problem summary
Render time is increased when using an item shader inside of a material mask.

The render time is also increased if Apply to Sub-Group is enabled. The render time is further increased if the material mask is placed above the base shader.

Customer reported version
modo.13.2v1

Customer reported platform
windows10

Steps to reproduce

1) Download and open the attached scene file.

2) Go to the Shader Tree and select the 'shader item inside...' group.

3) Press the F9 key to render the scene. Test this on each of the scenarios below:

• 'shader item inside' material mask disabled.
• 'shader item inside' material mask enabled and Apply to Sub-Group disabled.
• 'shader item inside' material mask enabled and Apply to Sub-Group enabled below the Base Shader item.
  
• 'shader item inside' material mask enabled and Apply to Sub-Group enabled above the Base Shader item.

4) Notice that the render times differ greatly.

Expected behaviour
The renders should take around the same time to complete.

Actual behaviour
Render times is greatly increased.

Workaround
Unknown.

Reproduced by support

This bug has been reproduced in:
13.2v1 - Windows 10 - Centos 7 - OSX 10.13

13.1v1 - Windows 10

13.0v1 - Windows 10

12.2v2 - Windows 10

12.1v2 - Windows 10

12.0v1 - Windows 10

11.2v3 - Windows 10

11.1v1 - Windows 10

11.0v3 - Windows 10

10.2v4 - Windows 10 - Centos 7 - OSX 10.13

Earliest version tested

10.2v4 - This issue appears to be in all versions of the product.