Partial revert of rest parameter desugaring.

src/arm64/code-stubs-arm64.cc

Index: src/arm64/code-stubs-arm64.cc
diff --git a/src/arm64/code-stubs-arm64.cc b/src/arm64/code-stubs-arm64.cc
index 9967847c62c38c01fb838687edafb6c962835c8c..b31fcaaaf2f0bb35faa80308871346c39602e545 100644
--- a/src/arm64/code-stubs-arm64.cc
+++ b/src/arm64/code-stubs-arm64.cc
@@ -2134,6 +2134,55 @@ void ArgumentsAccessStub::GenerateNewStrict(MacroAssembler* masm) {
 }
 
 
+void RestParamAccessStub::GenerateNew(MacroAssembler* masm) {
+  // Stack layout on entry.
+  //  jssp[0]:  language mode (tagged)
+  //  jssp[8]:  index of rest parameter (tagged)
+  //  jssp[16]: number of parameters (tagged)
+  //  jssp[24]: address of receiver argument
+  //
+  // Returns pointer to result object in x0.
+
+  // Get the stub arguments from the frame, and make an untagged copy of the
+  // parameter count.
+  Register language_mode_smi = x1;
+  Register rest_index_smi = x2;
+  Register param_count_smi = x3;
+  Register params = x4;
+  Register param_count = x13;
+  __ Pop(language_mode_smi, rest_index_smi, param_count_smi, params);
+  __ SmiUntag(param_count, param_count_smi);
+
+  // Test if arguments adaptor needed.
+  Register caller_fp = x11;
+  Register caller_ctx = x12;
+  Label runtime;
+  __ Ldr(caller_fp, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  __ Ldr(caller_ctx,
+         MemOperand(caller_fp, StandardFrameConstants::kContextOffset));
+  __ Cmp(caller_ctx, Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
+  __ B(ne, &runtime);
+
+  //   x1   language_mode_smi  language mode
+  //   x2   rest_index_smi     index of rest parameter
+  //   x3   param_count_smi    number of parameters passed to function (smi)
+  //   x4   params             pointer to parameters
+  //   x11  caller_fp          caller's frame pointer
+  //   x13  param_count        number of parameters passed to function
+
+  // Patch the argument length and parameters pointer.
+  __ Ldr(param_count_smi,
+         MemOperand(caller_fp, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  __ SmiUntag(param_count, param_count_smi);
+  __ Add(x10, caller_fp, Operand(param_count, LSL, kPointerSizeLog2));
+  __ Add(params, x10, StandardFrameConstants::kCallerSPOffset);
+
+  __ Bind(&runtime);
+  __ Push(params, param_count_smi, rest_index_smi, language_mode_smi);
+  __ TailCallRuntime(Runtime::kNewRestParam, 4, 1);
+}
+
+
 void RegExpExecStub::Generate(MacroAssembler* masm) {
 #ifdef V8_INTERPRETED_REGEXP
   __ TailCallRuntime(Runtime::kRegExpExec, 4, 1);