Addition evaluates before the ternary operator, which resulted in the wrong
sizes being computed.

Bug 28346104

Change-Id: Id28843132097a4fb1599eed19c05f479f16f1315
Reviewed-on: https://swiftshader-review.googlesource.com/5187Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>