a4d3be308c
The xsum library allows fast exact summation of double-precision values using small and large superaccumulators the description of the methods can be found at "Fast Exact Summation Using Small and Large Superaccumulators", by Radford M. Neal, available at https://arxiv.org/abs/1505.05571. This commit imports relevant parts of the code from the xsum lib in order to implement the Math.sumPrecise proposal (https://tc39.es/proposal-math-sum/) Differential Revision: https://phabricator.services.mozilla.com/D230053