Bug swiftshader:15

Change-Id: I3b20ba10e71c7813c35b16ae6c7382bfe4e0ae00
Reviewed-on: https://swiftshader-review.googlesource.com/7851Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8150Reviewed-by: Alexis Hétu <sugoi@google.com>