bmalloc: allocate small and medium objects using the same bump pointer class

bmalloc: allocate small and medium objects using the same bump pointer class
https://bugs.webkit.org/show_bug.cgi?id=136843

Reviewed by Gavin Barraclough.

4% speedup on MallocBench.

Now that medium-sized objects have dedicated per-size allocators, they
don't need to use an arbitrary bump pointer allocator. This means that
every allocator knows how many objects it will allocate from the start,
and we don't need a post-processing step to adjust refcounts based on
real allocation count.

* bmalloc.xcodeproj/project.pbxproj: Renamed SmallAllocator to BumpAllocator
since it's used for small and medium objects now.

* bmalloc/Allocator.cpp:
(bmalloc::Allocator::Allocator): Updated to use new interface.
(bmalloc::Allocator::scavenge): To "retire" an allocator, we just need
to make sure that we finish allocating all the objects in it.

(bmalloc::Allocator::allocateMedium):
(bmalloc::Allocator::allocateSlowCase):
(bmalloc::Allocator::retire): Deleted.
(bmalloc::Allocator::processSmallAllocatorLog): Deleted.
(bmalloc::Allocator::processMediumAllocatorLog): Deleted.
* bmalloc/Allocator.h:
(bmalloc::Allocator::allocateFastCase): Removed abstractions and data
used to post-process an allocator based on how many objects it allocated.

* bmalloc/BumpAllocator.h: Copied from Source/bmalloc/bmalloc/SmallAllocator.h.
(bmalloc::BumpAllocator::BumpAllocator):
(bmalloc::BumpAllocator::init):
(bmalloc::BumpAllocator::line):
(bmalloc::BumpAllocator::validate):
(bmalloc::BumpAllocator::allocate):
(bmalloc::BumpAllocator::refill):
(bmalloc::BumpAllocator::clear): Updated these functions to be agnostic
about the kinds of lines they allocate into. In some cases, the line
type must be provided as a template parameter by the caller.

(bmalloc::SmallAllocator::SmallAllocator): Deleted.
(bmalloc::SmallAllocator::line): Deleted.
(bmalloc::SmallAllocator::allocate): Deleted.
(bmalloc::SmallAllocator::objectCount): Deleted.
(bmalloc::SmallAllocator::derefCount): Deleted.
(bmalloc::SmallAllocator::refill): Deleted.
(bmalloc::SmallAllocator::clear): Deleted.

* bmalloc/ObjectType.h:
(bmalloc::isMedium):

* bmalloc/SmallAllocator.h:
(bmalloc::SmallAllocator::isNull): Deleted.
(bmalloc::SmallAllocator::canAllocate): Deleted.
(bmalloc::SmallAllocator::SmallAllocator): Deleted.
(bmalloc::SmallAllocator::line): Deleted.
(bmalloc::SmallAllocator::allocate): Deleted.
(bmalloc::SmallAllocator::objectCount): Deleted.
(bmalloc::SmallAllocator::derefCount): Deleted.
(bmalloc::SmallAllocator::refill): Deleted.
(bmalloc::SmallAllocator::clear): Deleted.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@173645 268f45cc-cd09-0410-ab3c-d52691b4dbfc