Bug swiftshader:15

Change-Id: I1391f656bce9b5cb09c4034df977ae4757e58843
Reviewed-on: https://swiftshader-review.googlesource.com/7955Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8160Reviewed-by: Alexis Hétu <sugoi@google.com>