[PATCH 3/3] Cache the result of find_file_and_directory

[Tom Tromey]

This changes the DWARF reader to cache the result of
find_file_and_directory.  This is not especially important now, but it
will help the new DWARF indexer.
---
 gdb/dwarf2/file-and-dir.h | 38 +++++++++++++++++++-------------------
 gdb/dwarf2/read.c         | 18 +++++++++++-------
 gdb/dwarf2/read.h         |  6 ++++++
 3 files changed, 36 insertions(+), 26 deletions(-)

diff --git a/gdb/dwarf2/file-and-dir.h b/gdb/dwarf2/file-and-dir.h
index 64d5a08bf0c..b64d304964a 100644
--- a/gdb/dwarf2/file-and-dir.h
+++ b/gdb/dwarf2/file-and-dir.h
@@ -35,23 +35,23 @@
 
 struct file_and_directory
 {
-  file_and_directory (const char *name_, const char *dir_)
-    : name (name_),
-      comp_dir (dir_)
+  file_and_directory (const char *name, const char *dir)
+    : m_name (name),
+      m_comp_dir (dir)
   {
   }
 
   /* Return true if the file name is unknown.  */
   bool is_unknown () const
   {
-    return name == nullptr;
+    return m_name == nullptr;
   }
 
   /* Set the compilation directory.  */
   void set_comp_dir (std::string &&dir)
   {
-    comp_dir_storage = std::move (dir);
-    comp_dir = nullptr;
+    m_comp_dir_storage = std::move (dir);
+    m_comp_dir = nullptr;
   }
 
   /* Fetch the compilation directory.  This may return NULL in some
@@ -60,48 +60,48 @@ struct file_and_directory
      you should call intern_comp_dir.  */
   const char *get_comp_dir () const
   {
-    if (!comp_dir_storage.empty ())
-      return comp_dir_storage.c_str ();
-    return comp_dir;
+    if (!m_comp_dir_storage.empty ())
+      return m_comp_dir_storage.c_str ();
+    return m_comp_dir;
   }
 
   /* If necessary, intern the compilation directory using OBJFILE's
      string cache.  Returns the compilation directory.  */
   const char *intern_comp_dir (struct objfile *objfile)
   {
-    if (!comp_dir_storage.empty ())
+    if (!m_comp_dir_storage.empty ())
       {
-	comp_dir = objfile->intern (comp_dir_storage);
-	comp_dir_storage.clear ();
+	m_comp_dir = objfile->intern (m_comp_dir_storage);
+	m_comp_dir_storage.clear ();
       }
-    return comp_dir;
+    return m_comp_dir;
   }
 
   /* Fetch the filename.  This never returns NULL.  */
   const char *get_name () const
   {
-    return name == nullptr ? "<unknown>" : name;
+    return m_name == nullptr ? "<unknown>" : m_name;
   }
 
   /* Set the filename.  */
-  void set_name (const char *name_)
+  void set_name (const char *name)
   {
-    name = name_;
+    m_name = name;
   }
 
 private:
 
   /* The filename.  This is never NULL.  */
-  const char *name;
+  const char *m_name;
 
   /* The compilation directory.  NULL if not known.  If we needed to
      compute a new string, it will be stored in the comp_dir_storage
      member, and this will be NULL.  Otherwise, points directly to the
      DW_AT_comp_dir string attribute.  */
-  const char *comp_dir;
+  const char *m_comp_dir;
 
   /* The compilation directory, if it needed to be allocated.  */
-  std::string comp_dir_storage;
+  std::string m_comp_dir_storage;
 };
 
 #endif /* GDB_DWARF2_FILE_AND_DIR_H */
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 5802fc0ef04..ff5758eb0a4 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -1537,8 +1537,8 @@ dwarf2_per_cu_data_deleter::operator() (dwarf2_per_cu_data *data)
     delete data;
 }
 
-static file_and_directory find_file_and_directory (struct die_info *die,
-						   struct dwarf2_cu *cu);
+static file_and_directory &find_file_and_directory
+     (struct die_info *die, struct dwarf2_cu *cu);
 
 static const char *compute_include_file_name
      (const struct line_header *lh,
@@ -3005,7 +3005,7 @@ dw2_get_file_names_reader (const struct die_reader_specs *reader,
       lh = dwarf_decode_line_header (line_offset, cu);
     }
 
-  file_and_directory fnd = find_file_and_directory (comp_unit_die, cu);
+  file_and_directory &fnd = find_file_and_directory (comp_unit_die, cu);
 
   int offset = 0;
   if (fnd.is_unknown ())
@@ -6988,7 +6988,7 @@ process_psymtab_comp_unit_reader (const struct die_reader_specs *reader,
   /* Allocate a new partial symbol table structure.  */
   gdb::unique_xmalloc_ptr<char> debug_filename;
   static const char artificial[] = "<artificial>";
-  file_and_directory fnd = find_file_and_directory (comp_unit_die, cu);
+  file_and_directory &fnd = find_file_and_directory (comp_unit_die, cu);
   if (strcmp (fnd.get_name (), artificial) == 0)
     {
       debug_filename.reset (concat (artificial, "@",
@@ -10474,9 +10474,12 @@ producer_is_gcc_lt_4_3 (struct dwarf2_cu *cu)
   return cu->producer_is_gcc_lt_4_3;
 }
 
-static file_and_directory
+static file_and_directory &
 find_file_and_directory (struct die_info *die, struct dwarf2_cu *cu)
 {
+  if (cu->per_cu->fnd != nullptr)
+    return *cu->per_cu->fnd;
+
   /* Find the filename.  Do not use dwarf2_name here, since the filename
      is not a source language identifier.  */
   file_and_directory res (dwarf2_string_attr (die, DW_AT_name, cu),
@@ -10488,7 +10491,8 @@ find_file_and_directory (struct die_info *die, struct dwarf2_cu *cu)
       && IS_ABSOLUTE_PATH (res.get_name ()))
     res.set_comp_dir (ldirname (res.get_name ()));
 
-  return res;
+  cu->per_cu->fnd.reset (new file_and_directory (std::move (res)));
+  return *cu->per_cu->fnd;
 }
 
 /* Handle DW_AT_stmt_list for a compilation unit.
@@ -10616,7 +10620,7 @@ read_file_scope (struct die_info *die, struct dwarf2_cu *cu)
     lowpc = highpc;
   lowpc = gdbarch_adjust_dwarf2_addr (gdbarch, lowpc + baseaddr);
 
-  file_and_directory fnd = find_file_and_directory (die, cu);
+  file_and_directory &fnd = find_file_and_directory (die, cu);
 
   cu->start_symtab (fnd.get_name (), fnd.intern_comp_dir (objfile), lowpc);
 
diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index 0afcda1c3b0..2f849d5f9a1 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -180,6 +180,12 @@ struct dwarf2_per_cu_data
      should be private, but we can't make it private at the moment.  */
   mutable comp_unit_head m_header {};
 
+  /* The file and directory for this CU.  This is cached so that we
+     don't need to re-examine the DWO in some situations.  This may be
+     nullptr, depending on the CU; for example a partial unit won't
+     have one.  */
+  std::unique_ptr<file_and_directory> fnd;
+
   /* When dwarf2_per_bfd::using_index is true, the 'quick' field
      is active.  Otherwise, the 'psymtab' field is active.  */
   union
-- 
2.31.1