implement op_get_rest_length so that we can allocate the rest array with the right size from the start
https://bugs.webkit.org/show_bug.cgi?id=151467

Reviewed by Geoffrey Garen and Mark Lam.

This patch implements op_get_rest_length which returns the length
that the rest parameter array will be. We're implementing this because
it might be a constant value in the presence of inlining in the DFG.
We will take advantage of this optimization opportunity in a future patch:
https://bugs.webkit.org/show_bug.cgi?id=151454
to emit better code for op_copy_rest.

op_get_rest_length has two operands: 
1) a destination
2) A constant indicating the number of parameters to skip when copying the rest array.

op_get_rest_length lowers to a JSConstant node when we're inlined
and not a varargs call (in this case, we statically know the arguments
length). When that condition isn't met, we lower op_get_rest_length to 
GetRestArray. GetRestArray produces its result as an int32.

* bytecode/BytecodeList.json:
* bytecode/BytecodeUseDef.h:
(JSC::computeUsesForBytecodeOffset):
(JSC::computeDefsForBytecodeOffset):
* bytecode/CodeBlock.cpp:
(JSC::CodeBlock::dumpBytecode):
* bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::emitNewArray):
(JSC::BytecodeGenerator::emitNewArrayWithSize):
(JSC::BytecodeGenerator::emitNewFunction):
(JSC::BytecodeGenerator::emitExpectedFunctionSnippet):
(JSC::BytecodeGenerator::emitRestParameter):
* bytecompiler/BytecodeGenerator.h:
* bytecompiler/NodesCodegen.cpp:
(JSC::RestParameterNode::emit):
* dfg/DFGAbstractInterpreterInlines.h:
(JSC::DFG::AbstractInterpreter<AbstractStateType>::executeEffects):
* dfg/DFGByteCodeParser.cpp:
(JSC::DFG::ByteCodeParser::parseBlock):
* dfg/DFGCapabilities.cpp:
(JSC::DFG::capabilityLevel):
* dfg/DFGClobberize.h:
(JSC::DFG::clobberize):
* dfg/DFGDoesGC.cpp:
(JSC::DFG::doesGC):
* dfg/DFGFixupPhase.cpp:
(JSC::DFG::FixupPhase::fixupNode):
* dfg/DFGMayExit.cpp:
(JSC::DFG::mayExit):
* dfg/DFGNode.h:
(JSC::DFG::Node::numberOfArgumentsToSkip):
* dfg/DFGNodeType.h:
* dfg/DFGOperations.cpp:
* dfg/DFGOperations.h:
* dfg/DFGPredictionPropagationPhase.cpp:
(JSC::DFG::PredictionPropagationPhase::propagate):
* dfg/DFGSafeToExecute.h:
(JSC::DFG::safeToExecute):
* dfg/DFGSpeculativeJIT.cpp:
(JSC::DFG::SpeculativeJIT::compileCopyRest):
(JSC::DFG::SpeculativeJIT::compileGetRestLength):
(JSC::DFG::SpeculativeJIT::compileNotifyWrite):
* dfg/DFGSpeculativeJIT.h:
(JSC::DFG::SpeculativeJIT::callOperation):
* dfg/DFGSpeculativeJIT32_64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* dfg/DFGSpeculativeJIT64.cpp:
(JSC::DFG::SpeculativeJIT::compile):
* ftl/FTLCapabilities.cpp:
(JSC::FTL::canCompile):
* ftl/FTLLowerDFGToLLVM.cpp:
(JSC::FTL::DFG::LowerDFGToLLVM::compileNode):
(JSC::FTL::DFG::LowerDFGToLLVM::compileCopyRest):
(JSC::FTL::DFG::LowerDFGToLLVM::compileGetRestLength):
(JSC::FTL::DFG::LowerDFGToLLVM::compileNewObject):
* jit/JIT.cpp:
(JSC::JIT::privateCompileMainPass):
* jit/JIT.h:
* jit/JITOpcodes.cpp:
(JSC::JIT::emit_op_copy_rest):
(JSC::JIT::emit_op_get_rest_length):
* llint/LowLevelInterpreter.asm:
* llint/LowLevelInterpreter32_64.asm:
* llint/LowLevelInterpreter64.asm:
* runtime/CommonSlowPaths.cpp:
(JSC::SLOW_PATH_DECL):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@192814 268f45cc-cd09-0410-ab3c-d52691b4dbfc
diff --git a/Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp b/Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp
index 4a7e2e7..242738e 100644
--- a/Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp
+++ b/Source/JavaScriptCore/bytecompiler/NodesCodegen.cpp
@@ -3483,7 +3483,8 @@
         return;
     }
 
-    RefPtr<RegisterID> restParameterArray = generator.emitRestParameter(generator.newTemporary(), m_numParametersToSkip);
+    RefPtr<RegisterID> restParameterArray = generator.newTemporary();
+    generator.emitRestParameter(restParameterArray.get(), m_numParametersToSkip);
     generator.emitProfileType(restParameterArray.get(), var, m_divotStart, m_divotEnd);
     RefPtr<RegisterID> scope = generator.emitResolveScope(nullptr, var);
     generator.emitExpressionInfo(m_divotEnd, m_divotStart, m_divotEnd);