Bug swiftshader:15

Change-Id: Iaa626705220e4bd9b3c744c7623f8b204022b716
Reviewed-on: https://swiftshader-review.googlesource.com/7397Tested-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>