* Add new prevector benchmarks.
This prepares for a series of two additional commits which optimize
prevector performance.
* Reduce redundant code of prevector and speed it up
In prevector.h, the code which like item_ptr(size()) apears in the loop.
Both item_ptr() and size() judge whether values are held directly or
indirectly, but in most cases it is sufficient to make that judgement
once outside the loop.
This PR adds 2 private function fill() which has the loop to initialize
by specified value (or iterator of the other prevector's element),
but don't call item_ptr() in their loop.
Other functions(assign(), constructor, operator=(), insert())
that has similar loop, call fill() instead of original loop.
Also, resize() was changed like fill(), but it calls the default
constructor for that element each time.
* Use memset() to optimize prevector::resize()
Further optimize prevector::resize() (which is called by a number of
other prevector methods) to use memset to initialize memory when the
prevector contains trivial types.
* fix bench/prevector.cpp
- PREVECTOR_TEST()
PREVECTOR_TEST macro should to call both
PrevectorXX<nontrivial_t>(state) and PrevectorXX<trivial_t>(state)
by specific "name" which given by parameter instead of calling
PrevectorResize<>() regardless of "name".
This patch changes "PrevectorResize<" of this macro to
"Prevector ## name<".
This is a backport of Core PR12549 and PR13598
Depends on D1844