CSE DataViewGet* DFG nodes

CSE DataViewGet* DFG nodes
https://bugs.webkit.org/show_bug.cgi?id=188768

Reviewed by Yusuke Suzuki.

JSTests:

* microbenchmarks/dataview-cse.js: Added.
(assert):
(test):
* stress/dataview-get-cse.js: Added.
(assert):
(test1.foo):
(test1):
(test2.foo):
(test2):
(test3.foo):
(test3):
(test4.foo):
(test4):
(test5.foo):
(test5):
(test6.foo):
(test6):

Source/JavaScriptCore:

This patch makes it so that we CSE DataViewGet* accesses. To do this,
I needed to add a third descriptor to HeapLocation to represent the
isLittleEndian child. This patch is neutral on compile time benchmarks,
and is a 50% speedup on a trivial CSE microbenchmark that I added.

* dfg/DFGClobberize.h:
(JSC::DFG::clobberize):
* dfg/DFGFixupPhase.cpp:
(JSC::DFG::FixupPhase::fixupNode):
* dfg/DFGHeapLocation.cpp:
(WTF::printInternal):
* dfg/DFGHeapLocation.h:
(JSC::DFG::HeapLocation::HeapLocation):
(JSC::DFG::HeapLocation::hash const):
(JSC::DFG::HeapLocation::operator== const):
(JSC::DFG::indexedPropertyLocForResultType):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@235515 268f45cc-cd09-0410-ab3c-d52691b4dbfc