[PATCH][RFC] Fix PRs 87362/87428

[Richard Biener <rguenther at suse dot de>]

Hi,

the following two patches both "fix" the immediate issue of gdb
asserting with

../../gdb/dwarf2read.c:9730: internal-error: void 
dw2_add_symbol_to_list(symbol*, pending**): Assertion `(*listhead) == NULL 
|| (SYMBOL_LANGUAGE ((*listhead)->symbol[0]) == SYMBOL_LANGUAGE (symbol))' 
failed.

on most LTO compiled objects now.  I tracked this down to us generating
bogus DWARF (as I read it), specifically an inline instance that is
output not as DW_TAG_inlined_subroutine but represented as
DW_TAG_lexical_block (but otherwise with same children and abstract
origin).  This is because we do have (quite a lot :/) inlined calls
with LOCATION_LOCUS (gimple_location (stmt)) == UNKNOWN_LOCATION
and thus inlined_function_outer_scope_p returning false on the
BLOCK the inliner generates.

A third yet untested alternative would be to store the combined
locus|BLOCK location in BLOCK_SOURCE_LOCATION and in
inlined_function_outer_scope_p check for literal UNKNOWN_LOCATION
instead of looking at LOCATION_LOCUS.  We'd have to properly
remap the locus in remap_block (which may be a chicken-and-egg issue)
to not run foul of what I fixed with r196542.  But somehow that
runs into issues with the new debug notes Alex added last year.
Similarly keying on BLOCK_ABSTRACT_ORIGIN rather than
BLOCK_SOURCE_LOCATION in inlined_function_outer_scope_p.

Any ideas?  The least fallout is probably produced by the
BUILTINS_LOCATION "hack" (but dwarf2out.c assumes that the
locations are sensible and thus will output some "interesting"
src-coords for the lexical block, <built-in>:0 respectively).

Thanks,
Richard.

2018-09-25  Richard Biener  <rguenther@suse.de>

	PR debug/87428
	PR debug/87362
	* tree-inline.c (expand_call_inline): When the location
	of the call is UNKNOWN_LOCATION drop debug info on the floor.

Index: gcc/tree-inline.c
===================================================================
--- gcc/tree-inline.c	(revision 264564)
+++ gcc/tree-inline.c	(working copy)
@@ -4525,7 +4525,8 @@ expand_call_inline (basic_block bb, gimp
      artificial decls inserted by the compiler itself.  We need to
      either link the inlined blocks into the caller block tree or
      not refer to them in any way to not break GC for locations.  */
-  if (gimple_block (stmt))
+  if (gimple_block (stmt)
+      && LOCATION_LOCUS (gimple_location (stmt)) != UNKNOWN_LOCATION)
     {
       id->block = make_node (BLOCK);
       BLOCK_ABSTRACT_ORIGIN (id->block) = fn;
@@ -4591,7 +4592,7 @@ expand_call_inline (basic_block bb, gimp
 
   if (DECL_INITIAL (fn))
     {
-      if (gimple_block (stmt))
+      if (id->block)
 	{
 	  tree *var;
 


2018-09-25  Richard Biener  <rguenther@suse.de>

	PR debug/87428
	PR debug/87362
	* tree-inline.c (expand_call_inline): When the location
	of the call is UNKNOWN_LOCATION use BUILTINS_LOCATION for
	the BLOCK_SOURCE_LOCATION of the inserted BLOCK to make
	inlined_function_outer_scope_p recognize it.

Index: gcc/tree-inline.c
===================================================================
--- gcc/tree-inline.c	(revision 264564)
+++ gcc/tree-inline.c	(working copy)
@@ -4527,10 +4527,12 @@ expand_call_inline (basic_block bb, gimp
      not refer to them in any way to not break GC for locations.  */
   if (gimple_block (stmt))
     {
+      location_t loc = LOCATION_LOCUS (gimple_location (stmt));
+      if (loc == UNKNOWN_LOCATION)
+	loc = BUILTINS_LOCATION;
       id->block = make_node (BLOCK);
       BLOCK_ABSTRACT_ORIGIN (id->block) = fn;
-      BLOCK_SOURCE_LOCATION (id->block) 
-	= LOCATION_LOCUS (gimple_location (stmt));
+      BLOCK_SOURCE_LOCATION (id->block) = loc;
       prepend_lexical_block (gimple_block (stmt), id->block);
     }