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

src/arm64/builtins-arm64.cc

 // Copyright 2013 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_ARM64
 
 #include "src/arm64/frames-arm64.h"
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
@@ skipping 31 matching lines @@
   __ Ldr(result, ContextMemOperand(result,
                                    Context::INTERNAL_ARRAY_FUNCTION_INDEX));
 }
 
 
 void Builtins::Generate_Adaptor(MacroAssembler* masm,
                                 CFunctionId id,
                                 BuiltinExtraArguments extra_args) {
   // ----------- S t a t e -------------
   //  -- x0                 : number of arguments excluding receiver
-  //  -- x1                 : called function (only guaranteed when
-  //                          extra_args requires it)
+  //                          (only guaranteed when the called function
+  //                           is not marked as DontAdaptArguments)
+  //  -- x1                 : called function
   //  -- sp[0]              : last argument
   //  -- ...
-  //  -- sp[4 * (argc - 1)] : first argument (argc == x0)
+  //  -- sp[4 * (argc - 1)] : first argument
   //  -- sp[4 * argc]       : receiver
   // -----------------------------------
   __ AssertFunction(x1);
 
   // 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?
   __ Ldr(cp, FieldMemOperand(x1, JSFunction::kContextOffset));
 
   // Insert extra arguments.
   int num_extra_args = 0;
   if (extra_args == NEEDS_CALLED_FUNCTION) {
     num_extra_args = 1;
     __ Push(x1);
   } else {
     DCHECK(extra_args == NO_EXTRA_ARGUMENTS);
   }
 
   // JumpToExternalReference expects x0 to contain the number of arguments
-  // including the receiver and the extra arguments.
+  // including the receiver and the extra arguments.  But x0 is only valid
+  // if the called function is marked as DontAdaptArguments, otherwise we
+  // need to load the argument count from the SharedFunctionInfo.
+  __ Ldr(x2, FieldMemOperand(x1, JSFunction::kSharedFunctionInfoOffset));
+  __ Ldrsw(
+      x2, FieldMemOperand(x2, SharedFunctionInfo::kFormalParameterCountOffset));
+  __ Cmp(x2, SharedFunctionInfo::kDontAdaptArgumentsSentinel);
+  __ Csel(x0, x0, x2, eq);
   __ Add(x0, x0, num_extra_args + 1);
+
   __ JumpToExternalReference(ExternalReference(id, masm->isolate()));
 }
 
 
 void Builtins::Generate_InternalArrayCode(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- x0     : number of arguments
   //  -- lr     : return address
   //  -- sp[...]: constructor arguments
   // -----------------------------------
@@ skipping 1862 matching lines @@
   }
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM