--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/file-prefix-map.c	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,132 @@
+/* Implementation of file prefix remapping support (-f*-prefix-map options).
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+   This program 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, or (at your option) any
+   later version.
+
+   This program 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 this program; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "diagnostic.h"
+#include "file-prefix-map.h"
+
+/* Structure recording the mapping from source file and directory names at
+   compile time to those to be embedded in the compilation result (debug
+   information, the __FILE__ macro expansion, etc).  */
+struct file_prefix_map
+{
+  const char *old_prefix;
+  const char *new_prefix;
+  size_t old_len;
+  size_t new_len;
+  struct file_prefix_map *next;
+};
+
+/* Record a file prefix mapping in the specified map.  ARG is the argument to
+   -f*-prefix-map and must be of the form OLD=NEW.  OPT is the option name
+   for diagnostics.  */
+static void
+add_prefix_map (file_prefix_map *&maps, const char *arg, const char *opt)
+{
+  file_prefix_map *map;
+  const char *p;
+
+  /* Note: looking for the last '='. The thinking is we can control the paths
+     inside our projects but not where the users build them.  */
+  p = strrchr (arg, '=');
+  if (!p)
+    {
+      error ("invalid argument %qs to %qs", arg, opt);
+      return;
+    }
+  map = XNEW (file_prefix_map);
+  map->old_prefix = xstrndup (arg, p - arg);
+  map->old_len = p - arg;
+  p++;
+  map->new_prefix = xstrdup (p);
+  map->new_len = strlen (p);
+  map->next = maps;
+  maps = map;
+}
+
+/* Perform user-specified mapping of filename prefixes.  Return the
+   GC-allocated new name corresponding to FILENAME or FILENAME if no
+   remapping was performed.  */
+
+static const char *
+remap_filename (file_prefix_map *maps, const char *filename)
+{
+  file_prefix_map *map;
+  char *s;
+  const char *name;
+  size_t name_len;
+
+  for (map = maps; map; map = map->next)
+    if (filename_ncmp (filename, map->old_prefix, map->old_len) == 0)
+      break;
+  if (!map)
+    return filename;
+  name = filename + map->old_len;
+  name_len = strlen (name) + 1;
+
+  s = (char *) ggc_alloc_atomic (name_len + map->new_len);
+  memcpy (s, map->new_prefix, map->new_len);
+  memcpy (s + map->new_len, name, name_len);
+  return s;
+}
+
+/* NOTE: if adding another -f*-prefix-map option then don't forget to
+   ignore it in DW_AT_producer (dwarf2out.c).  */
+
+/* Linked lists of file_prefix_map structures.  */
+static file_prefix_map *macro_prefix_maps; /* -fmacro-prefix-map  */
+static file_prefix_map *debug_prefix_maps; /* -fdebug-prefix-map  */
+
+/* Record a file prefix mapping for -fmacro-prefix-map.  */
+void
+add_macro_prefix_map (const char *arg)
+{
+  add_prefix_map (macro_prefix_maps, arg, "-fmacro-prefix-map");
+}
+
+/* Record a file prefix mapping for -fdebug-prefix-map.  */
+void
+add_debug_prefix_map (const char *arg)
+{
+  add_prefix_map (debug_prefix_maps, arg, "-fdebug-prefix-map");
+}
+
+/* Record a file prefix mapping for all -f*-prefix-map.  */
+void
+add_file_prefix_map (const char *arg)
+{
+  add_prefix_map (macro_prefix_maps, arg, "-ffile-prefix-map");
+  add_prefix_map (debug_prefix_maps, arg, "-ffile-prefix-map");
+}
+
+/* Remap using -fmacro-prefix-map.  Return the GC-allocated new name
+   corresponding to FILENAME or FILENAME if no remapping was performed.  */
+const char *
+remap_macro_filename (const char *filename)
+{
+  return remap_filename (macro_prefix_maps, filename);
+}
+
+/* Remap using -fdebug-prefix-map.  Return the GC-allocated new name
+   corresponding to FILENAME or FILENAME if no remapping was performed.  */
+const char *
+remap_debug_filename (const char *filename)
+{
+  return remap_filename (debug_prefix_maps, filename);
+}