[turbofan] Introduce JSCallForwardVarargs operator.

src/builtins/arm64/builtins-arm64.cc

Index: src/builtins/arm64/builtins-arm64.cc
diff --git a/src/builtins/arm64/builtins-arm64.cc b/src/builtins/arm64/builtins-arm64.cc
index 0cd1ec0a7d60ebf07ebdfa715da39df0e532f808..224c66800da4df8174930154b415fcbabec979c4 100644
--- a/src/builtins/arm64/builtins-arm64.cc
+++ b/src/builtins/arm64/builtins-arm64.cc
@@ -2333,6 +2333,72 @@ void Builtins::Generate_Apply(MacroAssembler* masm) {
   }
 }
 
+// static
+void Builtins::Generate_CallForwardVarargs(MacroAssembler* masm,
+                                           Handle<Code> code) {
+  // ----------- S t a t e -------------
+  //  -- x1    : the target to call (can be any Object)
+  //  -- x2    : start index (to support rest parameters)
+  //  -- lr    : return address.
+  //  -- sp[0] : thisArgument
+  // -----------------------------------
+
+  // Check if we have an arguments adaptor frame below the function frame.
+  Label arguments_adaptor, arguments_done;
+  __ Ldr(x3, MemOperand(fp, StandardFrameConstants::kCallerFPOffset));
+  __ Ldr(x4, MemOperand(x3, CommonFrameConstants::kContextOrFrameTypeOffset));
+  __ Cmp(x4, Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
+  __ B(eq, &arguments_adaptor);
+  {
+    __ Ldr(x0, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+    __ Ldr(x0, FieldMemOperand(x0, JSFunction::kSharedFunctionInfoOffset));
+    __ Ldrsw(x0, FieldMemOperand(
+                     x0, SharedFunctionInfo::kFormalParameterCountOffset));
+    __ Mov(x3, fp);
+  }
+  __ B(&arguments_done);
+  __ Bind(&arguments_adaptor);
+  {
+    // Just load the length from ArgumentsAdaptorFrame.
+    __ Ldrsw(x0, UntagSmiMemOperand(
+                     x3, ArgumentsAdaptorFrameConstants::kLengthOffset));
+  }
+  __ Bind(&arguments_done);
+
+  Label stack_empty, stack_done, stack_overflow;
+  __ Subs(x0, x0, x2);
+  __ B(le, &stack_empty);
+  {
+    // Check for stack overflow.
+    Generate_StackOverflowCheck(masm, x0, x2, &stack_overflow);
+
+    // Forward the arguments from the caller frame.
+    {
+      Label loop;
+      __ Add(x3, x3, kPointerSize);
+      __ Mov(x2, x0);
+      __ bind(&loop);
+      {
+        __ Ldr(x4, MemOperand(x3, x2, LSL, kPointerSizeLog2));
+        __ Push(x4);
+        __ Subs(x2, x2, 1);
+        __ B(ne, &loop);
+      }
+    }
+  }
+  __ B(&stack_done);
+  __ Bind(&stack_overflow);
+  __ TailCallRuntime(Runtime::kThrowStackOverflow);
+  __ Bind(&stack_empty);
+  {
+    // We just pass the receiver, which is already on the stack.
+    __ Mov(x0, 0);
+  }
+  __ Bind(&stack_done);
+
+  __ Jump(code, RelocInfo::CODE_TARGET);
+}
+
 namespace {
 
 // Drops top JavaScript frame and an arguments adaptor frame below it (if