Bug swiftshader:15

Change-Id: I27f7c2b9d87841a1eae0d9bc92fbe79b28c65982
Reviewed-on: https://swiftshader-review.googlesource.com/7773Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8146Reviewed-by: Alexis Hétu <sugoi@google.com>