[PATCH] Fix LTO early-debug ICE wrt abstract origin node streaming

[Richard Biener <rguenther@suse.de>]

The following fixes

Program received signal SIGSEGV, Segmentation fault.
0x0000000000af8edd in lto_get_decl_name_mapping (decl_data=0x0, 
    name=0x7ffff68dcbd0 "bar")
    at /space/rguenther/src/svn/trunk/gcc/lto-section-in.c:349
349       htab_t renaming_hash_table = decl_data->renaming_hash_table;
(gdb) bt
#0  0x0000000000af8edd in lto_get_decl_name_mapping (decl_data=0x0, 
    name=0x7ffff68dcbd0 "bar")
    at /space/rguenther/src/svn/trunk/gcc/lto-section-in.c:349
#1  0x0000000000af41b9 in copy_function_or_variable (node=0x7ffff6abfb80)
    at /space/rguenther/src/svn/trunk/gcc/lto-streamer-out.c:2233
#2  0x0000000000af4701 in lto_output ()
    at /space/rguenther/src/svn/trunk/gcc/lto-streamer-out.c:2328
#3  0x0000000000b6d909 in write_lto ()
    at /space/rguenther/src/svn/trunk/gcc/passes.c:2411
#4  0x0000000000b6e062 in ipa_write_optimization_summaries 
(encoder=0x2100ab0)
    at /space/rguenther/src/svn/trunk/gcc/passes.c:2615

I see quite often because I now stream DECL_ABSTRACT_ORIGIN from
the early compile.  Often the abstract origins have their bodies
removed as unreachable but LTRANS boundary compute happily
re-creates the cgraph nodes and tries to stream the bodies.  Which
obviously fails.

Below are two possible fixes (and in fact I believe that with
early LTO debug we do _not_ need to put abstract origins into the
LTRANS boundary at all - the abstract instance is available from
the early debug via the abstract origin decl).

Any preference?  I'm LTO bootstrapping the first one because it
looks bogus to use get_create here (did we add this for dwarf2out
ICEs with LTO?)

Maybe we want the cgraph_node::remove hunk as well and assert
in cgraph_node::create that we are not creating cgraph nodes
for DECL_ABSTRACT_P decls...

Thanks,
Richard.

2015-08-28  Richard Biener  <rguenther@suse.de>

	* lto-cgraph.c (compute_ltrans_boundary): Only put abstract
	origin nodes into the ltrans boundary if their body is still
	available.

Index: trunk/gcc/lto-cgraph.c
===================================================================
--- trunk.orig/gcc/lto-cgraph.c	2015-08-13 13:14:09.116378573 +0200
+++ trunk/gcc/lto-cgraph.c	2015-08-28 10:24:05.130397851 +0200
@@ -899,9 +899,12 @@ compute_ltrans_boundary (lto_symtab_enco
       if (DECL_ABSTRACT_ORIGIN (node->decl))
 	{
 	  struct cgraph_node *origin_node
-	  = cgraph_node::get_create (DECL_ABSTRACT_ORIGIN (node->decl));
-	  origin_node->used_as_abstract_origin = true;
-	  add_node_to (encoder, origin_node, true);
+	    = cgraph_node::get (DECL_ABSTRACT_ORIGIN (node->decl));
+	  if (origin_node)
+	    {
+	      origin_node->used_as_abstract_origin = true;
+	      add_node_to (encoder, origin_node, true);
+	    }
 	}
     }
   for (lsei = lsei_start_variable_in_partition (in_encoder);


2015-08-28  Richard Biener  <rguenther@suse.de>

	* cgraph.c (cgraph_node::remove): If the node was used as
	abstract origin mark the decl as abstract.
	* lto-cgraph.c (compute_ltrans_boundary): Do not put abstract
	nodes in the ltrans boundary.

Index: trunk/gcc/cgraph.c
===================================================================
--- trunk.orig/gcc/cgraph.c	2015-08-13 13:13:56.942263721 +0200
+++ trunk/gcc/cgraph.c	2015-08-28 10:03:06.841844184 +0200
@@ -1840,6 +1840,9 @@ cgraph_node::remove (void)
       lto_file_data = NULL;
     }
 
+  if (used_as_abstract_origin)
+    DECL_ABSTRACT_P (decl) = 1;
+
   decl = NULL;
   if (call_site_hash)
     {
Index: trunk/gcc/lto-cgraph.c
===================================================================
--- trunk.orig/gcc/lto-cgraph.c	2015-08-13 13:14:09.116378573 +0200
+++ trunk/gcc/lto-cgraph.c	2015-08-28 10:12:13.944867635 +0200
@@ -896,10 +896,12 @@ compute_ltrans_boundary (lto_symtab_enco
       lto_set_symtab_encoder_in_partition (encoder, node);
       create_references (encoder, node);
       /* For proper debug info, we need to ship the origins, too.  */
-      if (DECL_ABSTRACT_ORIGIN (node->decl))
+      if (DECL_ABSTRACT_ORIGIN (node->decl)
+	  /* ???  But we might have removed it!  */
+	  && ! DECL_ABSTRACT_P (DECL_ABSTRACT_ORIGIN (node->decl)))
 	{
 	  struct cgraph_node *origin_node
-	  = cgraph_node::get_create (DECL_ABSTRACT_ORIGIN (node->decl));
+	    = cgraph_node::get (DECL_ABSTRACT_ORIGIN (node->decl));
 	  origin_node->used_as_abstract_origin = true;
 	  add_node_to (encoder, origin_node, true);
 	}