Bug swiftshader:15

Change-Id: I2116fa6ad368c801e921becd89259b02b4ca68ce
Reviewed-on: https://swiftshader-review.googlesource.com/8251Reviewed-by: Nicolas Capens <capn@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <capn@google.com>