DFG JIT, Branch on integer can always be a 32-bit compare.

DFG JIT, Branch on integer can always be a 32-bit compare.
https://bugs.webkit.org/show_bug.cgi?id=69174

Reviewed by Sam Weinig.

if (shouldSpeculateInteger(node.child1()) && !isStrictInt32(node.child1())),
the JSVALUE64 JIT will currently compare all 64bits in the register, but in
these cases the DataFormat is always a JS boxed integer. In these cases we
can just compare the low 32bits anyway - no need to check the tag.
This allows the code to be unified with the JSVALUE32_64 JIT.

* dfg/DFGSpeculativeJIT32_64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* dfg/DFGSpeculativeJIT64.cpp:
(JSC::DFG::SpeculativeJIT::compile):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@96436 268f45cc-cd09-0410-ab3c-d52691b4dbfc