https://bugs.webkit.org/show_bug.cgi?id=120916

Reviewed by Oliver Hunt.
        
This adds support for Call/Construct by just calling out to C code that uses
the JSC::call/JSC::construct runtime functions for making calls. This is slow
and terrible, but it dramatically extends FTL coverage.
        
Supporting calls in a meaningful way meant also supporting
GlobalVarWatchpoint.
        
The extension of coverage helped to find a bunch of bugs:
        
- ObjectOrOtherUse was claimed to be supported in the FTL but speculate()
  didn't support it. That means that any node with an ObjectOrOtherUse edge
  that got DCE'd would cause the FTL to ICE.
        
- There was a bad fall-through compileCompareStrictEq() that led to ICE.
        
- The OSR exit reconstruction code was assuming it could do fast checks on
  node->child1() before even determining the type of node; that crashes if
  the node is HasVarArgs. Fixed by checking HasVarArgs first.
        
- The OSR exit compiler was using the wrong peekOffset for CArgumentGetter.
  The default is 1, which assumes that you didn't push anything onto the
  stack after getting called. The OSR exit thunks push FP, so the offset
  should be 2.
        
This passes stress tests and is probably huge performance regression if you
--useExperimentalFTL=true. The regression will be fixed in
https://bugs.webkit.org/show_bug.cgi?id=113621.

* dfg/DFGOperations.cpp:
* dfg/DFGOperations.h:
* ftl/FTLCapabilities.cpp:
(JSC::FTL::canCompile):
* ftl/FTLIntrinsicRepository.h:
* ftl/FTLLowerDFGToLLVM.cpp:
(JSC::FTL::LowerDFGToLLVM::compileNode):
(JSC::FTL::LowerDFGToLLVM::compileGlobalVarWatchpoint):
(JSC::FTL::LowerDFGToLLVM::compileCompareStrictEq):
(JSC::FTL::LowerDFGToLLVM::compileCallOrConstruct):
(JSC::FTL::LowerDFGToLLVM::speculate):
(JSC::FTL::LowerDFGToLLVM::speculateObjectOrOther):
(JSC::FTL::LowerDFGToLLVM::addExitArgumentForNode):
* ftl/FTLOSRExitCompiler.cpp:
(JSC::FTL::compileStub):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@155243 268f45cc-cd09-0410-ab3c-d52691b4dbfc