js/src/frontend/ValueUsage.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef frontend_ValueUsage_h
   8 #define frontend_ValueUsage_h
   9
  10 namespace js {
  11 namespace frontend {
  12
  13 // Used to control whether the expression result is used. This enables various
  14 // optimizations, for example it allows to emit JSOp::CallIgnoresRv for function
  15 // calls.
  16 enum class ValueUsage {
  17   // Assume the value of the current expression may be used. This is always
  18   // correct but prohibits optimizations like JSOp::CallIgnoresRv.
  19   WantValue,
  20
  21   // Pass this when emitting an expression if the expression's value is
  22   // definitely unused by later instructions. You must make sure the next
  23   // instruction is JSOp::Pop, a jump to a JSOp::Pop, or something similar.
  24   IgnoreValue
  25 };
  26
  27 } /* namespace frontend */
  28 } /* namespace js */
  29
  30 #endif /* frontend_ValueUsage_h */