This operation converts a big.Int to float64,
reporting the accuracy of the result, with
a fast path in hardware.
Fixes#56984
Change-Id: I86d0fb0e105a06a4009986f2f5fd87a4d446f6f9
Reviewed-on: https://go-review.googlesource.com/c/go/+/453115
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Alan Donovan <adonovan@google.com>
