Bug swiftshader:15

Change-Id: I5177113ad50ff2e1aa99f772d9254f7894ce5a61
Reviewed-on: https://swiftshader-review.googlesource.com/7870Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8152Reviewed-by: Alexis Hétu <sugoi@google.com>