[Interpreter] Allocate registers used as call arguments on-demand.

src/interpreter/bytecode-register-allocator.h

 // Copyright 2015 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.
 
 #ifndef V8_INTERPRETER_BYTECODE_REGISTER_ALLOCATOR_H_
 #define V8_INTERPRETER_BYTECODE_REGISTER_ALLOCATOR_H_
 
 #include "src/interpreter/bytecode-register.h"
 #include "src/interpreter/bytecodes.h"
 #include "src/zone/zone-containers.h"
@@ skipping 34 matching lines @@
   RegisterList NewRegisterList(int count) {
     RegisterList reg_list(next_register_index_, count);
     next_register_index_ += count;
     max_register_count_ = std::max(next_register_index_, max_register_count_);
     if (observer_) {
       observer_->RegisterListAllocateEvent(reg_list);
     }
     return reg_list;
   }
 
+  // Returns a growable register list.
+  RegisterList NewGrowableRegisterList() {
+    RegisterList reg_list(next_register_index_, 0);
+    return reg_list;
+  }
+
+  // Appends a new register to |reg_list| increasing it's count by one and
+  // returning the register added.
+  //
+  // Note: no other new registers must be currently allocated since the register
+  // list was originally allocated.
+  Register GrowRegisterList(RegisterList* reg_list) {
+    Register reg(NewRegister());
+    reg_list->IncrementRegisterCount();
+    // If the following CHECK fails then a register was allocated (and not
+    // freed) between the creation of the RegisterList and this call to add a
+    // Register.
+    CHECK_EQ(reg.index(), reg_list->last_register().index());
+    return reg;
+  }
+
   // Release all registers above |register_index|.
   void ReleaseRegisters(int register_index) {
     if (observer_) {
       observer_->RegisterListFreeEvent(
           RegisterList(register_index, next_register_index_ - register_index));
     }
     next_register_index_ = register_index;
   }
 
   // Returns true if the register |reg| is a live register.
@@ skipping 13 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(BytecodeRegisterAllocator);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 
 #endif  // V8_INTERPRETER_BYTECODE_REGISTER_ALLOCATOR_H_