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+/*
+
+Copyright (C) 2012 Max Brister <max@2bass.com>
+
+This file is part of Octave.
+
+Octave is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the
+Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+Octave is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with Octave; see the file COPYING.  If not, see
+<http://www.gnu.org/licenses/>.
+
+*/
+
+// Some utility classes and functions used throughout jit
+
+#if !defined (octave_jit_util_h)
+#define octave_jit_util_h 1
+
+#ifdef HAVE_LLVM
+
+#include <stdexcept>
+
+// we don't want to include llvm headers here, as they require
+// __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS be defined in the entire
+// compilation unit
+namespace llvm
+{
+  class Value;
+  class Module;
+  class FunctionPassManager;
+  class PassManager;
+  class ExecutionEngine;
+  class Function;
+  class BasicBlock;
+  class LLVMContext;
+  class Type;
+  class StructType;
+  class Twine;
+  class GlobalVariable;
+  class TerminatorInst;
+  class PHINode;
+
+  class ConstantFolder;
+
+  template <bool preserveNames>
+  class IRBuilderDefaultInserter;
+
+  template <bool preserveNames, typename T, typename Inserter>
+  class IRBuilder;
+
+typedef IRBuilder<true, ConstantFolder, IRBuilderDefaultInserter<true> >
+IRBuilderD;
+}
+
+class octave_base_value;
+class octave_builtin;
+class octave_value;
+class tree;
+class tree_expression;
+
+// thrown when we should give up on JIT and interpret
+class jit_fail_exception : public std::runtime_error
+{
+public:
+  jit_fail_exception (void) : std::runtime_error ("unknown"), mknown (false) {}
+  jit_fail_exception (const std::string& reason) : std::runtime_error (reason),
+                                                   mknown (true)
+  {}
+
+  bool known (void) const { return mknown; }
+private:
+  bool mknown;
+};
+
+// llvm doesn't provide this, and it's really useful for debugging
+std::ostream& operator<< (std::ostream& os, const llvm::Value& v);
+
+template <typename HOLDER_T, typename SUB_T>
+class jit_internal_node;
+
+// jit_internal_list and jit_internal_node implement generic embedded doubly
+// linked lists. List items extend from jit_internal_list, and can be placed
+// in nodes of type jit_internal_node. We use CRTP twice.
+template <typename LIST_T, typename NODE_T>
+class
+jit_internal_list
+{
+  friend class jit_internal_node<LIST_T, NODE_T>;
+public:
+  jit_internal_list (void) : use_head (0), use_tail (0), muse_count (0) {}
+
+  virtual ~jit_internal_list (void)
+  {
+    while (use_head)
+      use_head->stash_value (0);
+  }
+
+  NODE_T *first_use (void) const { return use_head; }
+
+  size_t use_count (void) const { return muse_count; }
+private:
+  NODE_T *use_head;
+  NODE_T *use_tail;
+  size_t muse_count;
+};
+
+// a node for internal linked lists
+template <typename LIST_T, typename NODE_T>
+class
+jit_internal_node
+{
+public:
+  typedef jit_internal_list<LIST_T, NODE_T> jit_ilist;
+
+  jit_internal_node (void) : mvalue (0), mnext (0), mprev (0) {}
+
+  ~jit_internal_node (void) { remove (); }
+
+  LIST_T *value (void) const { return mvalue; }
+
+  void stash_value (LIST_T *avalue)
+  {
+    remove ();
+
+    mvalue = avalue;
+
+    if (mvalue)
+      {
+        jit_ilist *ilist = mvalue;
+        NODE_T *sthis = static_cast<NODE_T *> (this);
+        if (ilist->use_head)
+          {
+            ilist->use_tail->mnext = sthis;
+            mprev = ilist->use_tail;
+          }
+        else
+          ilist->use_head = sthis;
+
+        ilist->use_tail = sthis;
+        ++ilist->muse_count;
+      }
+  }
+
+  NODE_T *next (void) const { return mnext; }
+
+  NODE_T *prev (void) const { return mprev; }
+private:
+  void remove ()
+  {
+    if (mvalue)
+      {
+        jit_ilist *ilist = mvalue;
+        if (mprev)
+          mprev->mnext = mnext;
+        else
+          // we are the use_head
+          ilist->use_head = mnext;
+
+        if (mnext)
+          mnext->mprev = mprev;
+        else
+          // we are the use tail
+          ilist->use_tail = mprev;
+
+        mnext = mprev = 0;
+        --ilist->muse_count;
+        mvalue = 0;
+      }
+  }
+
+  LIST_T *mvalue;
+  NODE_T *mnext;
+  NODE_T *mprev;
+};
+
+// Use like: isa<jit_phi> (value)
+// basically just a short cut type typing dyanmic_cast.
+template <typename T, typename U>
+bool isa (U *value)
+{
+  return dynamic_cast<T *> (value);
+}
+
+#define JIT_ASSIGN_ARG(i) the_args[i] = arg ## i;
+#define JIT_EXPAND(ret, fname, type, isconst, N)                        \
+  ret fname (JIT_PARAM_ARGS OCT_MAKE_DECL_LIST (type, arg, N)) isconst  \
+  {                                                                     \
+    std::vector<type> the_args (N);                                     \
+    OCT_ITERATE_MACRO (JIT_ASSIGN_ARG, N);                              \
+    return fname (JIT_PARAMS the_args);                                 \
+  }
+
+#endif
+#endif