[3/10] introduce psymtab users

[Tom Tromey <tromey at redhat dot com>]

Adding support for imported PUs means modifying both symtabs and
psymtabs to understand the inclusions.

This patch adds some basic infrastructure to psymtabs.  It adds a
"users" field which the psymtab readers can set.  Then, it changes the
psymtab code to handle included psymtabs properly.

There are a few cases to consider.  I did this by auditing all the code
in psymtab.c.

When doing lookups using the file name, we can just ignore PUs.

When doing a lookup by name or by PC, it is ok to find a PU.  However,
we have a rule that we can only expand a full CU, so we modify
psymtab_to_symtab to find a user (any will do) of the PU.

Then, finally, there is some hair in expand_symtabs_matching_via_partial
to search PUs while searching CUs.

This patch has no immediate effect, because no psymtab readers are
updated yet.

Tom

>From 9d29b92217dd4e363d88f7cbc357d4cf9d28e51b Mon Sep 17 00:00:00 2001
From: Tom Tromey <tromey@redhat.com>
Date: Wed, 18 Apr 2012 14:49:36 -0600
Subject: [PATCH 03/10] introduce psymtab users notion

	* psymtab.c (partial_map_expand_apply): Add assertion.
	(partial_map_symtabs_matching_filename): Skip included psymtabs.
	(psymtab_to_symtab): Find unshared psymtab.
	(dump_psymtab): Print including psymtabs.
	(PST_NOT_SEARCHED, PST_SEARCHED_AND_FOUND)
	(PST_SEARCHED_AND_NOT_FOUND): New constants.
	(recursively_search_psymtabs): New function.
	(expand_symtabs_matching_via_partial): Use it.
	* psympriv.h (struct partial_symtab) <users, searched_flag>: New
	fields.
---
 gdb/psympriv.h |   29 +++++++++
 gdb/psymtab.c  |  177 +++++++++++++++++++++++++++++++++++++++++--------------
 2 files changed, 161 insertions(+), 45 deletions(-)

diff --git a/gdb/psympriv.h b/gdb/psympriv.h
index df7b874..5515d6c 100644
--- a/gdb/psympriv.h
+++ b/gdb/psympriv.h
@@ -111,6 +111,31 @@ struct partial_symtab
 
   int number_of_dependencies;
 
+  /* If NULL, this is an ordinary partial symbol table.
+
+     If non-NULL, this holds a NULL-terminated vector of includers of
+     this partial symbol table, and this partial symbol table is a
+     shared one.
+
+     A shared psymtab is one that is referenced by multiple other
+     psymtabs, and which conceptually has its contents directly
+     included in those.
+
+     Shared psymtabs have special semantics.  When a search finds a
+     symbol in a shared table, we instead return one of the non-shared
+     tables that include this one.
+
+     A shared psymtabs can be referred to by other shared ones.
+
+     The psymtabs that refer to a shared psymtab will list the shared
+     psymtab in their 'dependencies' array.
+
+     In DWARF terms, a shared psymtab is a DW_TAG_partial_unit; but
+     of course using a name based on that would be too confusing, so
+     "shared" was chosen instead.  */
+
+  struct partial_symtab **users;
+
   /* Global symbol list.  This list will be sorted after readin to
      improve access.  Binary search will be the usual method of
      finding a symbol within it.  globals_offset is an integer offset
@@ -142,6 +167,10 @@ struct partial_symtab
 
   unsigned char psymtabs_addrmap_supported;
 
+  /* A flag that is temporarily used when searching psymtabs.  */
+
+  unsigned char searched_flag;
+
   /* Pointer to symtab eventually allocated for this source file, 0 if
      !readin or if we haven't looked for the symtab after it was readin.  */
 
diff --git a/gdb/psymtab.c b/gdb/psymtab.c
index 9620de8..9e64275 100644
--- a/gdb/psymtab.c
+++ b/gdb/psymtab.c
@@ -135,6 +135,10 @@ partial_map_expand_apply (struct objfile *objfile,
 {
   struct symtab *last_made = objfile->symtabs;
 
+  /* Shared psymtabs should never be seen here.  Instead they should
+     be handled properly by the caller.  */
+  gdb_assert (pst->users == NULL);
+
   /* Don't visit already-expanded psymtabs.  */
   if (pst->readin)
     return 0;
@@ -165,6 +169,11 @@ partial_map_symtabs_matching_filename (struct objfile *objfile,
 
   ALL_OBJFILE_PSYMTABS_REQUIRED (objfile, pst)
   {
+    /* We can skip shared psymtabs here, because any file name will be
+       attached to the unshared psymtab.  */
+    if (pst->users != NULL)
+      continue;
+
     if (FILENAME_CMP (name, pst->filename) == 0
 	|| (!is_abs && compare_filenames_for_search (pst->filename,
 						     name, name_len)))
@@ -760,6 +769,11 @@ lookup_partial_symbol (struct partial_symtab *pst, const char *name,
 static struct symtab *
 psymtab_to_symtab (struct partial_symtab *pst)
 {
+  /* If it is a shared psymtab, find an unshared psymtab that includes
+     it.  Any such psymtab will do.  */
+  while (pst->users != NULL)
+    pst = pst->users[0];
+
   /* If it's been looked up before, return it.  */
   if (pst->symtab)
     return pst->symtab;
@@ -1000,6 +1014,16 @@ dump_psymtab (struct objfile *objfile, struct partial_symtab *psymtab,
       fprintf_filtered (outfile, " %s\n",
 			psymtab->dependencies[i]->filename);
     }
+  if (psymtab->users != NULL)
+    {
+      fprintf_filtered (outfile, "  Shared partial symtab with users:\n");
+      for (i = 0; psymtab->users[i] != NULL; ++i)
+	{
+	  fprintf_filtered (outfile, "    ");
+	  gdb_print_host_address (psymtab->users[i], outfile);
+	  fprintf_filtered (outfile, "\n");
+	}
+    }
   if (psymtab->n_global_syms > 0)
     {
       print_partial_symbols (gdbarch,
@@ -1236,6 +1260,102 @@ map_matching_symbols_psymtab (const char *name, domain_enum namespace,
     }
 }	    
 
+/* A convenience enum to give names to some constants used in
+   recursively_search_psymtabs.  */
+
+enum
+  {
+    PST_NOT_SEARCHED,
+    PST_SEARCHED_AND_FOUND,
+    PST_SEARCHED_AND_NOT_FOUND
+  };
+
+/* A helper for expand_symtabs_matching_via_partial that handles
+   searching included psymtabs.  */
+
+static int
+recursively_search_psymtabs (struct partial_symtab *ps,
+			     struct objfile *objfile,
+			     enum search_domain kind,
+			     int (*name_matcher) (const char *, void *),
+			     void *data)
+{
+  struct partial_symbol **psym;
+  struct partial_symbol **bound, **gbound, **sbound;
+  int keep_going = 1;
+  int result = PST_SEARCHED_AND_NOT_FOUND;
+  int i;
+
+  if (ps->searched_flag != PST_NOT_SEARCHED)
+    return ps->searched_flag == PST_SEARCHED_AND_FOUND;
+
+  /* Recurse into shared psymtabs first, because they may have already
+     been searched, and this could save some time.  */
+  for (i = 0; i < ps->number_of_dependencies; ++i)
+    {
+      int r;
+
+      /* Skip non-shared dependencies, these are handled elsewhere.  */
+      if (ps->dependencies[i]->users == NULL)
+	continue;
+
+      r = recursively_search_psymtabs (ps->dependencies[i],
+				       objfile, kind, name_matcher, data);
+      if (r != 0)
+	{
+	  ps->searched_flag = PST_SEARCHED_AND_FOUND;
+	  return 1;
+	}
+    }
+
+  gbound = (objfile->global_psymbols.list
+	    + ps->globals_offset + ps->n_global_syms);
+  sbound = (objfile->static_psymbols.list
+	    + ps->statics_offset + ps->n_static_syms);
+  bound = gbound;
+
+  /* Go through all of the symbols stored in a partial
+     symtab in one loop.  */
+  psym = objfile->global_psymbols.list + ps->globals_offset;
+  while (keep_going)
+    {
+      if (psym >= bound)
+	{
+	  if (bound == gbound && ps->n_static_syms != 0)
+	    {
+	      psym = objfile->static_psymbols.list + ps->statics_offset;
+	      bound = sbound;
+	    }
+	  else
+	    keep_going = 0;
+	  continue;
+	}
+      else
+	{
+	  QUIT;
+
+	  if ((kind == ALL_DOMAIN
+	       || (kind == VARIABLES_DOMAIN
+		   && SYMBOL_CLASS (*psym) != LOC_TYPEDEF
+		   && SYMBOL_CLASS (*psym) != LOC_BLOCK)
+	       || (kind == FUNCTIONS_DOMAIN
+		   && SYMBOL_CLASS (*psym) == LOC_BLOCK)
+	       || (kind == TYPES_DOMAIN
+		   && SYMBOL_CLASS (*psym) == LOC_TYPEDEF))
+	      && (*name_matcher) (SYMBOL_SEARCH_NAME (*psym), data))
+	    {
+	      /* Found a match, so notify our caller.  */
+	      result = PST_SEARCHED_AND_FOUND;
+	      keep_going = 0;
+	    }
+	}
+      psym++;
+    }
+
+  ps->searched_flag = result;
+  return result == PST_SEARCHED_AND_FOUND;
+}
+
 static void
 expand_symtabs_matching_via_partial
   (struct objfile *objfile,
@@ -1246,60 +1366,27 @@ expand_symtabs_matching_via_partial
 {
   struct partial_symtab *ps;
 
+  /* Clear the search flags.  */
   ALL_OBJFILE_PSYMTABS_REQUIRED (objfile, ps)
     {
-      struct partial_symbol **psym;
-      struct partial_symbol **bound, **gbound, **sbound;
-      int keep_going = 1;
+      ps->searched_flag = PST_NOT_SEARCHED;
+    }
 
+  ALL_OBJFILE_PSYMTABS_REQUIRED (objfile, ps)
+    {
       if (ps->readin)
 	continue;
 
-      if (file_matcher && ! (*file_matcher) (ps->filename, data))
+      /* We skip shared psymtabs because file-matching doesn't apply
+	 to them; but we search them later in the loop.  */
+      if (ps->users != NULL)
 	continue;
 
-      gbound = objfile->global_psymbols.list
-	+ ps->globals_offset + ps->n_global_syms;
-      sbound = objfile->static_psymbols.list
-	+ ps->statics_offset + ps->n_static_syms;
-      bound = gbound;
+      if (file_matcher && ! (*file_matcher) (ps->filename, data))
+	continue;
 
-      /* Go through all of the symbols stored in a partial
-	 symtab in one loop.  */
-      psym = objfile->global_psymbols.list + ps->globals_offset;
-      while (keep_going)
-	{
-	  if (psym >= bound)
-	    {
-	      if (bound == gbound && ps->n_static_syms != 0)
-		{
-		  psym = objfile->static_psymbols.list + ps->statics_offset;
-		  bound = sbound;
-		}
-	      else
-		keep_going = 0;
-	      continue;
-	    }
-	  else
-	    {
-	      QUIT;
-
-	      if ((kind == ALL_DOMAIN
-		   || (kind == VARIABLES_DOMAIN
-		       && SYMBOL_CLASS (*psym) != LOC_TYPEDEF
-		       && SYMBOL_CLASS (*psym) != LOC_BLOCK)
-		   || (kind == FUNCTIONS_DOMAIN
-		       && SYMBOL_CLASS (*psym) == LOC_BLOCK)
-		   || (kind == TYPES_DOMAIN
-		       && SYMBOL_CLASS (*psym) == LOC_TYPEDEF))
-		  && (*name_matcher) (SYMBOL_SEARCH_NAME (*psym), data))
-		{
-		  psymtab_to_symtab (ps);
-		  keep_going = 0;
-		}
-	    }
-	  psym++;
-	}
+      if (recursively_search_psymtabs (ps, objfile, kind, name_matcher, data))
+	psymtab_to_symtab (ps);
     }
 }
 
-- 
1.7.7.6