DFG::Edge should have more bits for UseKind, and DFG::Allocator should be simpler
https://bugs.webkit.org/show_bug.cgi?id=110722

Reviewed by Oliver Hunt.
        
This rolls out the DFG::Allocator part of http://trac.webkit.org/changeset/143654,
and changes Edge to have more room for UseKinds and possibly other things.
        
This is performance-neutral on both 32-bit and 64-bit. It reduces the size of
DFG::Node on 64-bit (by virtue of getting rid of the 16-byte alignment of Node)
and increases it slightly on 32-bit (by 4 bytes total - 16-byte alignment led to
80 bytes, but the base size of Node plus the 12 bytes of new m_encodedWords in
Edge gets 84 bytes). But, it will mean that we don't have to increase Node by
another 16 bytes if we ever want to add more UseKinds or other things to Edge.

* dfg/DFGAllocator.h:
(DFG):
(Allocator):
(JSC::DFG::Allocator::Region::headerSize):
(JSC::DFG::Allocator::Region::numberOfThingsPerRegion):
(JSC::DFG::Allocator::Region::data):
(JSC::DFG::Allocator::Region::isInThisRegion):
(JSC::DFG::::Allocator):
(JSC::DFG::::~Allocator):
(JSC::DFG::::allocate):
(JSC::DFG::::free):
(JSC::DFG::::freeAll):
(JSC::DFG::::reset):
(JSC::DFG::::indexOf):
(JSC::DFG::::allocatorOf):
(JSC::DFG::::bumpAllocate):
(JSC::DFG::::freeListAllocate):
(JSC::DFG::::allocateSlow):
(JSC::DFG::::freeRegionsStartingAt):
(JSC::DFG::::startBumpingIn):
* dfg/DFGEdge.h:
(JSC::DFG::Edge::Edge):
(Edge):
(JSC::DFG::Edge::node):
(JSC::DFG::Edge::setNode):
(JSC::DFG::Edge::useKindUnchecked):
(JSC::DFG::Edge::setUseKind):
(JSC::DFG::Edge::operator==):
(JSC::DFG::Edge::operator!=):
(JSC::DFG::Edge::makeWord):
* dfg/DFGNodeAllocator.h:
(DFG):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143958 268f45cc-cd09-0410-ab3c-d52691b4dbfc