[calls] Consistent call protocol for calls.

src/x64/lithium-codegen-x64.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_X64
 
 #include "src/base/bits.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/cpu-profiler.h"
@@ skipping 3393 matching lines @@
   bool can_invoke_directly =
       dont_adapt_arguments || formal_parameter_count == arity;
 
   Register function_reg = rdi;
   LPointerMap* pointers = instr->pointer_map();
 
   if (can_invoke_directly) {
     // Change context.
     __ movp(rsi, FieldOperand(function_reg, JSFunction::kContextOffset));
 
-    // Set rax to arguments count if adaption is not needed. Assumes that rax
-    // is available to write to at this point.
-    if (dont_adapt_arguments) {
-      __ Set(rax, arity);
-    }
+    // Always initialize rax to the number of actual arguments.
+    __ Set(rax, arity);
 
     // Invoke function.
     if (function.is_identical_to(info()->closure())) {
       __ CallSelf();
     } else {
       __ Call(FieldOperand(function_reg, JSFunction::kCodeEntryOffset));
     }
 
     // Set up deoptimization.
     RecordSafepointWithLazyDeopt(instr, RECORD_SIMPLE_SAFEPOINT, 0);
@@ skipping 42 matching lines @@
     }
     generator.AfterCall();
   }
 }
 
 
 void LCodeGen::DoCallJSFunction(LCallJSFunction* instr) {
   DCHECK(ToRegister(instr->function()).is(rdi));
   DCHECK(ToRegister(instr->result()).is(rax));
 
-  if (instr->hydrogen()->pass_argument_count()) {
-    __ Set(rax, instr->arity());
-  }
+  __ Set(rax, instr->arity());
 
   // Change context.
   __ movp(rsi, FieldOperand(rdi, JSFunction::kContextOffset));
 
   LPointerMap* pointers = instr->pointer_map();
   SafepointGenerator generator(this, pointers, Safepoint::kLazyDeopt);
 
   bool is_self_call = false;
   if (instr->hydrogen()->function()->IsConstant()) {
     Handle<JSFunction> jsfun = Handle<JSFunction>::null();
@@ skipping 2452 matching lines @@
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64