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/bytecode/CodeBlock.cpp b/Source/JavaScriptCore/bytecode/CodeBlock.cpp
index fca6301..9e1386e 100644
--- a/Source/JavaScriptCore/bytecode/CodeBlock.cpp
+++ b/Source/JavaScriptCore/bytecode/CodeBlock.cpp
@@ -783,7 +783,16 @@
         }
         case op_copy_rest: {
             int r0 = (++it)->u.operand;
+            int r1 = (++it)->u.operand;
+            unsigned argumentOffset = (++it)->u.unsignedValue;
             printLocationAndOp(out, exec, location, it, "copy_rest");
+            out.printf("%s, %s, ", registerName(r0).data(), registerName(r1).data());
+            out.printf("ArgumentsOffset: %u", argumentOffset);
+            break;
+        }
+        case op_get_rest_length: {
+            int r0 = (++it)->u.operand;
+            printLocationAndOp(out, exec, location, it, "get_rest_length");
             out.printf("%s, ", registerName(r0).data());
             unsigned argumentOffset = (++it)->u.unsignedValue;
             out.printf("ArgumentsOffset: %u", argumentOffset);