Bug swiftshader:15

Change-Id: I59bfec356b04ebc2ff7d8507d39ec8f18c57e42a
Reviewed-on: https://swiftshader-review.googlesource.com/7830Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8149Reviewed-by: Alexis Hétu <sugoi@google.com>