Did you find the answer to the original question? It sounds pitiful that Vivado should not provide ieee.math.real for compile time calculations as state-of-the-art tools use to. However, even if math_real.vhd is not shipped with the compiler, it's just a text file that can be added to your project.
In situations like this, wouldnt it have been much easier and quicker just to create a small design example and test for yourself? I suspected the Vivado answer you posted was related to synthesis of stuff like registers using the real data type, not constants or setup. Otherwise it would have been out of step with many other synthesisor and Im sure someone would have picked it up.
You assume that I simply stumbled upon the post in #3 and decided to ask here - I'm not that lazy...
I'm in the process of migrating a design from Altera to Xilinx and in one of my source files "math.real" is included.
As you probably know - Vivado does live parsing tests on any file you add to the project (without actually compiling it). The line marked with "math.real" is highlighted as error in the Vivado text editor.
I'm using verstion 2017.2 - Is it possible that you're using something newer ?