[PATCH] Fix -fdebug-types-section ICE, PR91887

[Richard Biener]

The following makes sure we correctly identify a parm DIE created
early in a formal parameter pack during late annotation.

Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.

OK?

Thanks,
Richard.

2019-10-16  Richard Biener  <rguenther@suse.de>

	PR debug/91887
	* dwarf2out.c (gen_formal_parameter_die): Also try to match
	context_die against a DW_TAG_GNU_formal_parameter_pack parent.

	* g++.dg/debug/dwarf2/pr91887.C: New testcase.

Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c	(revision 277053)
+++ gcc/dwarf2out.c	(working copy)
@@ -22284,19 +22284,18 @@ gen_formal_parameter_die (tree node, tre
       /* If the contexts differ, we may not be talking about the same
 	 thing.
 	 ???  When in LTO the DIE parent is the "abstract" copy and the
-	 context_die is the specification "copy".  But this whole block
-	 should eventually be no longer needed.  */
-      if (parm_die && parm_die->die_parent != context_die && !in_lto_p)
+	 context_die is the specification "copy".  */
+      if (parm_die
+	  && parm_die->die_parent != context_die
+	  && (parm_die->die_parent->die_tag != DW_TAG_GNU_formal_parameter_pack
+	      || parm_die->die_parent->die_parent != context_die)
+	  && !in_lto_p)
 	{
-	  if (!DECL_ABSTRACT_P (node))
-	    {
-	      /* This can happen when creating an inlined instance, in
-		 which case we need to create a new DIE that will get
-		 annotated with DW_AT_abstract_origin.  */
-	      parm_die = NULL;
-	    }
-	  else
-	    gcc_unreachable ();
+	  gcc_assert (!DECL_ABSTRACT_P (node));
+	  /* This can happen when creating a concrete instance, in
+	     which case we need to create a new DIE that will get
+	     annotated with DW_AT_abstract_origin.  */
+	  parm_die = NULL;
 	}
 
       if (parm_die && parm_die->die_parent == NULL)
Index: gcc/testsuite/g++.dg/debug/dwarf2/pr91887.C
===================================================================
--- gcc/testsuite/g++.dg/debug/dwarf2/pr91887.C	(nonexistent)
+++ gcc/testsuite/g++.dg/debug/dwarf2/pr91887.C	(working copy)
@@ -0,0 +1,12 @@
+// { dg-do compile }
+// { dg-require-effective-target c++11 }
+// { dg-options "-g -fdebug-types-section" }
+class A {
+public:
+  A();
+  template <typename U> A(U);
+};
+template <class> struct B { typedef A type; };
+template <class R, typename... Args>
+int Bind(R(Args...), typename B<Args>::type...) { return 0; }
+void KeepBufferRefs(A, A) { A a, b(Bind(KeepBufferRefs, a, b)); }