Merge pull request #17434 from mppf/astr-unordered_map
Update astr mechanism to use C++11 unordered_map
Now that the compiler sources require C++11, we can use
std::unordered_map. This PR adjusts the hashtable we use to unique
astr) to use
std::unordered_map and, while there, better
factor/optimize a few related functions.
In my experiments, this PR reduces Hello World compile times by about
0.1s. But, besides that, it migrates one use of the custom
Map to a
standard C++ type. We would like, over time, to migrate all uses of the
Map and then remove it.
Reviewed by @leekillough - thanks!
[x] full local testing