Bug swiftshader:15

Change-Id: Ib22831ce669c68a790664839d18ea05668e90992
Reviewed-on: https://swiftshader-review.googlesource.com/7971Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8166Reviewed-by: Alexis Hétu <sugoi@google.com>