Bug swiftshader:15

Change-Id: Ie20d881be8710d2c8e8e996ae670f7f40481f13c
Reviewed-on: https://swiftshader-review.googlesource.com/7990Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8167Reviewed-by: Alexis Hétu <sugoi@google.com>