Fixes bug swiftshader:72.

Change-Id: I4fcc6c47ec8561150c88fea200aeb6baf9534c00
Reviewed-on: https://swiftshader-review.googlesource.com/10511Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Ben Vanik <benvanik@google.com>