Make FastNewFunctionContextStub take slots parameter

src/full-codegen/x64/full-codegen-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/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 156 matching lines @@
       __ Push(info->scope()->GetScopeInfo(info->isolate()));
       __ CallRuntime(Runtime::kNewScriptContext);
       PrepareForBailoutForId(BailoutId::ScriptContext(),
                              BailoutState::TOS_REGISTER);
       // The new target value is not used, clobbering is safe.
       DCHECK_NULL(info->scope()->new_target_var());
     } else {
       if (info->scope()->new_target_var() != nullptr) {
         __ Push(rdx);  // Preserve new target.
       }
-      if (slots <= FastNewFunctionContextStub::kMaximumSlots) {
-        FastNewFunctionContextStub stub(isolate(), slots);
-        __ CallStub(&stub);
-        // Result of FastNewFunctionContextStub is always in new space.
-        need_write_barrier = false;
-      } else {
-        __ Push(rdi);
-        __ CallRuntime(Runtime::kNewFunctionContext);
-      }
+      FastNewFunctionContextStub stub(isolate());
+      __ Set(FastNewFunctionContextDescriptor::SlotsRegister(), slots);
+      __ CallStub(&stub);
+      // Result of FastNewFunctionContextStub is always in new space.
+      need_write_barrier = false;
       if (info->scope()->new_target_var() != nullptr) {
         __ Pop(rdx);  // Restore new target.
       }
     }
     function_in_register = false;
     // Context is returned in rax.  It replaces the context passed to us.
     // It's saved in the stack and kept live in rsi.
     __ movp(rsi, rax);
     __ movp(Operand(rbp, StandardFrameConstants::kContextOffset), rax);
 
@@ skipping 3466 matching lines @@
   DCHECK_EQ(
       isolate->builtins()->OnStackReplacement()->entry(),
       Assembler::target_address_at(call_target_address, unoptimized_code));
   return ON_STACK_REPLACEMENT;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64