re PR debug/81307 (g++.dg/debug/debug9.C -gstabs FAILs)

	PR debug/81307
	* dbxout.c (lastlineno): New variable.
	(dbx_debug_hooks): Use dbxout_switch_text_section as
	switch_text_section debug hook.
	(dbxout_function_end): Switch to current_function_section
	rather than function_section.  If crtl->has_bb_partition,
	output just one N_FUN, depending on in_cold_section_p.
	(dbxout_source_line): Remember last lineno in lastlineno.
	(dbxout_switch_text_section): New function.
	(dbxout_function_decl): Adjust dbxout_block caller.
	(dbx_block_with_cold_children): New function.
	(dbxout_block): Return true if any LBRAC/RBRAC have been
	emitted.  Use dbx_block_with_cold_children at depth == 0
	in second partition.  Add PARENT_BLOCKNUM argument, pass
	it optionally adjusted to children.  Output LBRAC/RBRAC
	around recursive call only if the block is in the current
	partition, if not and anything was output, emit empty
	range LBRAC/RBRAC.
	* final.c (final_scan_insn): Compute cold_function_name
	before calling switch_text_section debug hook.  Call
	that hook even if dwarf2out_do_frame if not emitting
	dwarf debug info.

	* g++.dg/debug/debug9.C: Remove -fno-reorder-blocks-and-partition
	workaround.

From-SVN: r255161

gcc/ChangeLog

 2017-11-27  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/81307
+	* dbxout.c (lastlineno): New variable.
+	(dbx_debug_hooks): Use dbxout_switch_text_section as
+	switch_text_section debug hook.
+	(dbxout_function_end): Switch to current_function_section
+	rather than function_section.  If crtl->has_bb_partition,
+	output just one N_FUN, depending on in_cold_section_p.
+	(dbxout_source_line): Remember last lineno in lastlineno.
+	(dbxout_switch_text_section): New function.
+	(dbxout_function_decl): Adjust dbxout_block caller.
+	(dbx_block_with_cold_children): New function.
+	(dbxout_block): Return true if any LBRAC/RBRAC have been
+	emitted.  Use dbx_block_with_cold_children at depth == 0
+	in second partition.  Add PARENT_BLOCKNUM argument, pass
+	it optionally adjusted to children.  Output LBRAC/RBRAC
+	around recursive call only if the block is in the current
+	partition, if not and anything was output, emit empty
+	range LBRAC/RBRAC.
+	* final.c (final_scan_insn): Compute cold_function_name
+	before calling switch_text_section debug hook.  Call
+	that hook even if dwarf2out_do_frame if not emitting
+	dwarf debug info.
+
 	PR target/83100
 	* varasm.c (bss_initializer_p): Return true for DECL_COMMON
 	TREE_READONLY decls.

gcc/dbxout.c

@@ -244,6 +244,10 @@ static GTY(()) int source_label_number = 1;
 
 static GTY(()) const char *lastfile;
 
+/* Last line number mentioned in a NOTE insn.  */
+
+static GTY(()) unsigned int lastlineno;
+
 /* Used by PCH machinery to detect if 'lastfile' should be reset to
    base_input_file.  */
 static GTY(()) int lastfile_is_base;
@@ -334,6 +338,7 @@ static void debug_free_queue (void);
 
 static void dbxout_source_line (unsigned int, unsigned int, const char *,
 				int, bool);
+static void dbxout_switch_text_section (void);
 static void dbxout_begin_prologue (unsigned int, unsigned int, const char *);
 static void dbxout_source_file (const char *);
 static void dbxout_function_end (tree);
@@ -380,7 +385,7 @@ const struct gcc_debug_hooks dbx_debug_hooks =
   dbxout_handle_pch,		         /* handle_pch */
   debug_nothing_rtx_insn,	         /* var_location */
   debug_nothing_tree,			 /* size_function */
-  debug_nothing_void,                    /* switch_text_section */
+  dbxout_switch_text_section,            /* switch_text_section */
   debug_nothing_tree_tree,		 /* set_name */
   0,                                     /* start_end_main_source_file */
   TYPE_SYMTAB_IS_ADDRESS                 /* tree_type_symtab_field */
@@ -902,7 +907,7 @@ dbxout_function_end (tree decl ATTRIBUTE_UNUSED)
 
   /* The Lscope label must be emitted even if we aren't doing anything
      else; dbxout_block needs it.  */
-  switch_to_section (function_section (current_function_decl));
+  switch_to_section (current_function_section ());
 
   /* Convert Lscope into the appropriate format for local labels in case
      the system doesn't insert underscores in front of user generated
@@ -923,11 +928,12 @@ dbxout_function_end (tree decl ATTRIBUTE_UNUSED)
   if (crtl->has_bb_partition)
     {
       dbxout_begin_empty_stabs (N_FUN);
-      dbxout_stab_value_label_diff (crtl->subsections.hot_section_end_label,
-				    crtl->subsections.hot_section_label);
-      dbxout_begin_empty_stabs (N_FUN);
-      dbxout_stab_value_label_diff (crtl->subsections.cold_section_end_label,
-				    crtl->subsections.cold_section_label);
+      if (in_cold_section_p)
+	dbxout_stab_value_label_diff (crtl->subsections.cold_section_end_label,
+				      crtl->subsections.cold_section_label);
+      else
+	dbxout_stab_value_label_diff (crtl->subsections.hot_section_end_label,
+				      crtl->subsections.hot_section_label);
     }
   else
     {
@@ -1215,7 +1221,7 @@ dbxout_handle_pch (unsigned at_end)
 
 #if defined (DBX_DEBUGGING_INFO)
 
-static void dbxout_block (tree, int, tree);
+static bool dbxout_block (tree, int, tree, int);
 
 /* Output debugging info to FILE to switch to sourcefile FILENAME.  */
 
@@ -1289,6 +1295,60 @@ dbxout_source_line (unsigned int lineno, unsigned int column ATTRIBUTE_UNUSED,
   else
     dbxout_stabd (N_SLINE, lineno);
 #endif
+  lastlineno = lineno;
+}
+
+/* Unfortunately, at least when emitting relative addresses, STABS
+   has no way to express multiple partitions.  Represent a function
+   as two functions in this case.  */
+
+static void
+dbxout_switch_text_section (void)
+{
+  /* The N_FUN tag at the end of the function is a GNU extension,
+     which may be undesirable, and is unnecessary if we do not have
+     named sections.  */
+  in_cold_section_p = !in_cold_section_p;
+  switch_to_section (current_function_section ());
+  dbxout_block (DECL_INITIAL (current_function_decl), 0,
+		DECL_ARGUMENTS (current_function_decl), -1);
+  dbxout_function_end (current_function_decl);
+  in_cold_section_p = !in_cold_section_p;
+
+  switch_to_section (current_function_section ());
+
+  tree context = decl_function_context (current_function_decl);
+  extern tree cold_function_name;
+
+  dbxout_begin_complex_stabs ();
+  stabstr_I (cold_function_name);
+  stabstr_S (":f");
+
+  tree type = TREE_TYPE (current_function_decl);
+  if (TREE_TYPE (type))
+    dbxout_type (TREE_TYPE (type), 0);
+  else
+    dbxout_type (void_type_node, 0);
+
+  if (context != 0)
+    {
+      stabstr_C (',');
+      stabstr_I (cold_function_name);
+      stabstr_C (',');
+      stabstr_I (DECL_NAME (context));
+    }
+
+  dbxout_finish_complex_stabs (current_function_decl, N_FUN, 0,
+			       crtl->subsections.cold_section_label, 0);
+
+  /* pre-increment the scope counter */
+  scope_labelno++;
+
+  dbxout_source_line (lastlineno, 0, lastfile, 0, true);
+  /* Output function begin block at function scope, referenced
+     by dbxout_block, dbxout_source_line and dbxout_function_end.  */
+  emit_pending_bincls_if_required ();
+  targetm.asm_out.internal_label (asm_out_file, "LFBB", scope_labelno);
 }
 
 /* Describe the beginning of an internal block within a function.  */
@@ -1322,7 +1382,7 @@ dbxout_function_decl (tree decl)
 #ifndef DBX_FUNCTION_FIRST
   dbxout_begin_function (decl);
 #endif
-  dbxout_block (DECL_INITIAL (decl), 0, DECL_ARGUMENTS (decl));
+  dbxout_block (DECL_INITIAL (decl), 0, DECL_ARGUMENTS (decl), -1);
   dbxout_function_end (decl);
 }
 
@@ -3664,6 +3724,26 @@ dbx_output_rbrac (const char *label,
     dbxout_stab_value_label (label);
 }
 
+/* Return true is at least one block among BLOCK, its children or siblings
+   which has TREE_USED, TREE_ASM_WRITTEN and BLOCK_IN_COLD_SECTION_P
+   set.  If there is none, clear TREE_USED bit on such blocks.  */
+
+static bool
+dbx_block_with_cold_children (tree block)
+{
+  bool ret = false;
+  for (; block; block = BLOCK_CHAIN (block))
+    if (TREE_USED (block) && TREE_ASM_WRITTEN (block))
+      {
+	bool children = dbx_block_with_cold_children (BLOCK_SUBBLOCKS (block));
+	if (BLOCK_IN_COLD_SECTION_P (block) || children)
+	  ret = true;
+	else
+	  TREE_USED (block) = false;
+      }
+  return ret;
+}
+
 /* Output everything about a symbol block (a BLOCK node
    that represents a scope level),
    including recursive output of contained blocks.
@@ -3679,22 +3759,31 @@ dbx_output_rbrac (const char *label,
    except for the outermost block.
 
    Actually, BLOCK may be several blocks chained together.
-   We handle them all in sequence.  */
+   We handle them all in sequence.
 
-static void
-dbxout_block (tree block, int depth, tree args)
+   Return true if we emitted any LBRAC/RBRAC.  */
+
+static bool
+dbxout_block (tree block, int depth, tree args, int parent_blocknum)
 {
+  bool ret = false;
   char begin_label[20];
   /* Reference current function start using LFBB.  */
   ASM_GENERATE_INTERNAL_LABEL (begin_label, "LFBB", scope_labelno);
 
-  while (block)
+  /* If called for the second partition, ignore blocks that don't have
+     any children in the second partition.  */
+  if (crtl->has_bb_partition && in_cold_section_p && depth == 0)
+    dbx_block_with_cold_children (block);
+
+  for (; block; block = BLOCK_CHAIN (block))
     {
       /* Ignore blocks never expanded or otherwise marked as real.  */
       if (TREE_USED (block) && TREE_ASM_WRITTEN (block))
 	{
 	  int did_output;
 	  int blocknum = BLOCK_NUMBER (block);
+	  int this_parent = parent_blocknum;
 
 	  /* In dbx format, the syms of a block come before the N_LBRAC.
 	     If nothing is output, we don't need the N_LBRAC, either.  */
@@ -3708,11 +3797,13 @@ dbxout_block (tree block, int depth, tree args)
 	     the block.  Use the block's tree-walk order to generate
 	     the assembler symbols LBBn and LBEn
 	     that final will define around the code in this block.  */
-	  if (did_output)
+	  if (did_output
+	      && BLOCK_IN_COLD_SECTION_P (block) == in_cold_section_p)
 	    {
 	      char buf[20];
 	      const char *scope_start;
 
+	      ret = true;
 	      if (depth == 0)
 		/* The outermost block doesn't get LBB labels; use
 		   the LFBB local symbol emitted by dbxout_begin_prologue.  */
@@ -3721,16 +3812,21 @@ dbxout_block (tree block, int depth, tree args)
 		{
 		  ASM_GENERATE_INTERNAL_LABEL (buf, "LBB", blocknum);
 		  scope_start = buf;
+		  this_parent = blocknum;
 		}
 
 	      dbx_output_lbrac (scope_start, begin_label);
 	    }
 
 	  /* Output the subblocks.  */
-	  dbxout_block (BLOCK_SUBBLOCKS (block), depth + 1, NULL_TREE);
+	  bool children
+	    = dbxout_block (BLOCK_SUBBLOCKS (block), depth + 1, NULL_TREE,
+			    this_parent);
+	  ret |= children;
 
 	  /* Refer to the marker for the end of the block.  */
-	  if (did_output)
+	  if (did_output
+	      && BLOCK_IN_COLD_SECTION_P (block) == in_cold_section_p)
 	    {
 	      char buf[100];
 	      if (depth == 0)
@@ -3743,9 +3839,29 @@ dbxout_block (tree block, int depth, tree args)
 
 	      dbx_output_rbrac (buf, begin_label);
 	    }
+	  else if (did_output && !children)
+	    {
+	      /* If we emitted any vars and didn't output any LBRAC/RBRAC,
+		 either at this level or any lower level, we need to emit
+		 an empty LBRAC/RBRAC pair now.  */
+	      char buf[20];
+	      const char *scope_start;
+
+	      ret = true;
+	      if (parent_blocknum == -1)
+		scope_start = begin_label;
+	      else
+		{
+		  ASM_GENERATE_INTERNAL_LABEL (buf, "LBB", parent_blocknum);
+		  scope_start = buf;
+		}
+
+	      dbx_output_lbrac (scope_start, begin_label);
+	      dbx_output_rbrac (scope_start, begin_label);
+	    }
 	}
-      block = BLOCK_CHAIN (block);
     }
+  return ret;
 }
 
 /* Output the information about a function and its arguments and result.

gcc/final.c

@@ -2210,8 +2210,17 @@ final_scan_insn (rtx_insn *insn, FILE *file, int optimize_p ATTRIBUTE_UNUSED,
 	case NOTE_INSN_SWITCH_TEXT_SECTIONS:
 	  in_cold_section_p = !in_cold_section_p;
 
+	  if (in_cold_section_p)
+	    cold_function_name
+	      = clone_function_name (current_function_decl, "cold");
+
 	  if (dwarf2out_do_frame ())
-	    dwarf2out_switch_text_section ();
+	    {
+	      dwarf2out_switch_text_section ();
+	      if (!dwarf2_debug_info_emitted_p (current_function_decl)
+		  && !DECL_IGNORED_P (current_function_decl))
+		debug_hooks->switch_text_section ();
+	    }
 	  else if (!DECL_IGNORED_P (current_function_decl))
 	    debug_hooks->switch_text_section ();
 
@@ -2223,8 +2232,6 @@ final_scan_insn (rtx_insn *insn, FILE *file, int optimize_p ATTRIBUTE_UNUSED,
 	     suffixing "cold" to the original function's name.  */
 	  if (in_cold_section_p)
 	    {
-	      cold_function_name
-		= clone_function_name (current_function_decl, "cold");
 #ifdef ASM_DECLARE_COLD_FUNCTION_NAME
 	      ASM_DECLARE_COLD_FUNCTION_NAME (asm_out_file,
 					      IDENTIFIER_POINTER

gcc/testsuite/ChangeLog

 2017-11-27  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/81307
+	* g++.dg/debug/debug9.C: Remove -fno-reorder-blocks-and-partition
+	workaround.
+
 	PR target/83100
 	* gcc.dg/pr83100-1.c: New test.
 	* gcc.dg/pr83100-2.c: New test.

gcc/testsuite/g++.dg/debug/debug9.C

 /* { dg-do assemble } */
-/* Partitioning causes hot/cold section emission and breaks stabs
-   debugging.  */
-/* { dg-additional-options "-fno-reorder-blocks-and-partition" } */
-
-
 /* This testcase requires entries in the debug_range section in DWARF which
    refer to a vague linkage function.  */