Thread-local storage and Performance

[dsimcha]

Has D's builtin TLS been optimized in the past 6 months to year?  I had
benchmarked it awhile back when optimizing some code that I wrote and
discovered it was significantly slower than regular globals (the kind that are
now __gshared).  Now, at least on Windows, it seems that there is no
discernible difference and if anything, TLS is slightly faster than __gshared.
 What's changed?