Bug swiftshader:15

Change-Id: I4fa5356109e35ac13f9f8d5a97e9059262901051
Reviewed-on: https://swiftshader-review.googlesource.com/7950Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8156Reviewed-by: Alexis Hétu <sugoi@google.com>