Bug swiftshader:15

Change-Id: I785e31724e802a3ed1bca75186e012ccc7cb336e
Reviewed-on: https://swiftshader-review.googlesource.com/7850Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8151Reviewed-by: Alexis Hétu <sugoi@google.com>