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

src/mips/builtins-mips.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_MIPS
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
 #include "src/runtime/runtime.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 -------------
   //  -- a0                 : number of arguments excluding receiver
-  //  -- a1                 : called function (only guaranteed when
-  //  --                      extra_args requires it)
+  //                          (only guaranteed when the called function
+  //                           is not marked as DontAdaptArguments)
+  //  -- a1                 : called function
   //  -- sp[0]              : last argument
   //  -- ...
   //  -- sp[4 * (argc - 1)] : first argument
   //  -- sp[4 * agrc]       : receiver
   // -----------------------------------
   __ AssertFunction(a1);
 
   // 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?
   __ lw(cp, FieldMemOperand(a1, JSFunction::kContextOffset));
 
   // Insert extra arguments.
   int num_extra_args = 0;
   if (extra_args == NEEDS_CALLED_FUNCTION) {
     num_extra_args = 1;
     __ push(a1);
   } else {
     DCHECK(extra_args == NO_EXTRA_ARGUMENTS);
   }
 
   // JumpToExternalReference expects a0 to contain the number of arguments
-  // including the receiver and the extra arguments.
+  // including the receiver and the extra arguments.  But a0 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;
+  __ lw(a2, FieldMemOperand(a1, JSFunction::kSharedFunctionInfoOffset));
+  __ lw(a2,
+        FieldMemOperand(a2, SharedFunctionInfo::kFormalParameterCountOffset));
+  __ SmiUntag(a2);
+  __ Branch(&argc, ne, a2,
+            Operand(SharedFunctionInfo::kDontAdaptArgumentsSentinel));
+  __ Addu(a0, a2, num_extra_args + 1);
+  __ jmp(&done_argc);
+  __ bind(&argc);
   __ Addu(a0, a0, num_extra_args + 1);
+  __ bind(&done_argc);
+
   __ JumpToExternalReference(ExternalReference(id, masm->isolate()));
 }
 
 
 // Load the built-in InternalArray function from the current context.
 static void GenerateLoadInternalArrayFunction(MacroAssembler* masm,
                                               Register result) {
   // Load the native context.
 
   __ lw(result,
@@ skipping 1827 matching lines @@
   }
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS