forked from OSchip/llvm-project
fde79b40c2
unordered_set::emplace and unordered_map::emplace construct a node, then try to insert it. If insertion fails, the node gets deleted. To avoid this unnecessary malloc traffic, check to see if the argument to emplace has the appropriate key_type. If so, we can use that key directly and delay the malloc until we're sure we're inserting something new. Test updates by Eric Fiselier, who rewrote the old allocation tests to include the new cases. There are two orthogonal future directions: 1. Apply the same optimization to set and map. 2. Extend the optimization to when the argument is not key_type, but can be converted to it without side effects. Ideally, we could do this whenever key_type is trivially destructible and the argument is trivially convertible to key_type, but in practise the relevant type traits "blow up sometimes". At least, we should catch a few simple cases (such as when both are primitive types). llvm-svn: 263746 |
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