Bug swiftshader:15

Change-Id: I9ed683b6d122183c4313d2bf609fd7c14bf5e387
Reviewed-on: https://swiftshader-review.googlesource.com/7958Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8163Reviewed-by: Alexis Hétu <sugoi@google.com>