[builtins] Make sure argument count is always valid for C++ builtins.

src/x64/builtins-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
 
 namespace v8 {
 namespace internal {
 
 
 #define __ ACCESS_MASM(masm)
 
 
 void Builtins::Generate_Adaptor(MacroAssembler* masm,
                                 CFunctionId id,
                                 BuiltinExtraArguments extra_args) {
   // ----------- S t a t e -------------
   //  -- rax                 : number of arguments excluding receiver
-  //  -- rdi                 : called function (only guaranteed when
-  //                           extra_args requires it)
+  //                           (only guaranteed when the called function
+  //                            is not marked as DontAdaptArguments)
+  //  -- rdi                 : called function
   //  -- rsp[0]              : return address
   //  -- rsp[8]              : last argument
   //  -- ...
-  //  -- rsp[8 * argc]       : first argument (argc == rax)
+  //  -- rsp[8 * argc]       : first argument
   //  -- rsp[8 * (argc + 1)] : receiver
   // -----------------------------------
   __ AssertFunction(rdi);
 
   // Make sure we operate in the context of the called function (for example
   // ConstructStubs implemented in C++ will be run in the context of the caller
   // instead of the callee, due to the way that [[Construct]] is defined for
   // ordinary functions).
   // TODO(bmeurer): Can we make this more robust?
   __ movp(rsi, FieldOperand(rdi, JSFunction::kContextOffset));
 
   // Insert extra arguments.
   int num_extra_args = 0;
   if (extra_args == NEEDS_CALLED_FUNCTION) {
     num_extra_args = 1;
     __ PopReturnAddressTo(kScratchRegister);
     __ Push(rdi);
     __ PushReturnAddressFrom(kScratchRegister);
   } else {
     DCHECK(extra_args == NO_EXTRA_ARGUMENTS);
   }
 
   // JumpToExternalReference expects rax to contain the number of arguments
-  // including the receiver and the extra arguments.
+  // including the receiver and the extra arguments.  But rax is only valid
+  // if the called function is marked as DontAdaptArguments, otherwise we
+  // need to load the argument count from the SharedFunctionInfo.
+  Label argc, done_argc;
+  __ movp(rdx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
+  __ LoadSharedFunctionInfoSpecialField(
+      rbx, rdx, SharedFunctionInfo::kFormalParameterCountOffset);
+  __ cmpp(rbx, Immediate(SharedFunctionInfo::kDontAdaptArgumentsSentinel));
+  __ j(equal, &argc, Label::kNear);
+  __ leap(rax, Operand(rbx, num_extra_args + 1));
+  __ jmp(&done_argc, Label::kNear);
+  __ bind(&argc);
   __ addp(rax, Immediate(num_extra_args + 1));
+  __ bind(&done_argc);
+
   __ JumpToExternalReference(ExternalReference(id, masm->isolate()), 1);
 }
 
 
 static void CallRuntimePassFunction(
     MacroAssembler* masm, Runtime::FunctionId function_id) {
   FrameScope scope(masm, StackFrame::INTERNAL);
   // Push a copy of the function onto the stack.
   __ Push(rdi);
   // Function is also the parameter to the runtime call.
@@ skipping 1854 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64