fix -fcompare-debug OBJ_TYPE_REF dumps of linker plugin-less LTO builds

[Alexandre Oliva <aoliva at redhat dot com>]

There are two patches below.  Each one of them fixes the problem
described below by itself, and both would also fix it together.

The former preserves OBJ_TYPE_REF type info in all dumps that
should/would have it, even after TYPE_BINFO is reset to release its
memory.  To that end, it requires changes to the middle end, and a few
changes to front-ends that set TYPE_BINFO.

The latter creates a special case for -fcompare-debug to hide this
irrelevant compilation artifact, but it's a far more localized change,
with zero compile-time impact, and it paves the way to introduce other
compare-debug-specific IR dumping changes to exclude other artifacts
from leading to -fcompare-debug errors.

I've regstrapped each of them on x86_64-linux-gnu and i686-linux-gnu.

Ok to install the former?

Ok to install the latter?


-fcompare-debug OBJ_TYPE_REF: introduce TYPE_BINFO_EVER_SET et al

In LTO compilation of e.g. libstdc++-prettyprint/shared_ptr, we reset
TYPE_BINFO of certain types, to release memory, depending on whether
we are to generate debug info.

Alas, TYPE_BINFO is tested by OBJ_TYPE_REF dumpers, to decide whether
or not to dump its class.  This causes -fcompare-debug to fail,
because the two different rounds of compilation will have opposite
debug information generation requests, and thus will decide
differently whether to reset TYPE_BINFO long before the
-fcompare-debug dumps.

What really matters for the virtual_method_call_p test is whether
TYPE_BINFO is set, or was ever set, and this is the function that
decides whether to dump the type of the OBJ_TYPE_REF.  So, I introduce
memory in TYPE_BINFO of whether it was ever set, in a way that doesn't
take up more space, but slows down former uses of TYPE_BINFO a bit:
its (new) setter macro won't let it go back to NULL, and a (new) reset
macro will make it point back to the node itself, so that we know it's
neither NULL nor a TREE_BINFO, and won't stop any garbage from being
collected.

With this patch, the aforementioned libstdc++ test passes even with
-fcompare-debug.


I suppose there might be remaining uses of TYPE_BINFO that could
benefit from testing TYPE_BINFO_EVER_SET instead, but I haven't
investigated them all, and those I have only guarded uses of BINFO_*,
so they can't change.


for  gcc/ChangeLog

	* tree.h (TYPE_BINFO): Return NULL if it's not a TREE_BINFO
	object.
	(TYPE_BINFO_EVER_SET): Test that it's not NULL.
	(SET_TYPE_BINFO): Don't change it from non-NULL to NULL.
	(RESET_TYPE_BINFO): Set it to a non-TREE_BINFO, not NULL.
	* ipa-devirt.c (set_type_binfo): Use SET_TYPE_BINFO.
	* tree.c (free_lang_data_in_type): Use RESET_TYPE_BINFO.
	(virtual_method_call_p): Test TYPE_BINFO_EVER_SET.

for  gcc/cp/ChangeLog

	* class.c (fixup_type_variants): Use SET_TYPE_BINFO.
	* decl.c (xref_basetypes): Likewise.

for gcc/objc/ChangeLog

	* objc-act.c (objc_xref_basetypes): Use SET_TYPE_BINFO.
---
 gcc/cp/class.c      |    2 +-
 gcc/cp/decl.c       |    2 +-
 gcc/ipa-devirt.c    |    2 +-
 gcc/objc/objc-act.c |    4 ++--
 gcc/tree.c          |    4 ++--
 gcc/tree.h          |   24 +++++++++++++++++++++++-
 6 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 98e62c6ad450..4f92204ba504 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -1927,7 +1927,7 @@ fixup_type_variants (tree t)
 
       TYPE_POLYMORPHIC_P (variants) = TYPE_POLYMORPHIC_P (t);
 
-      TYPE_BINFO (variants) = TYPE_BINFO (t);
+      SET_TYPE_BINFO (variants, TYPE_BINFO (t));
 
       /* Copy whatever these are holding today.  */
       TYPE_VFIELD (variants) = TYPE_VFIELD (t);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 0ce8f2d34358..8cd39375cf3c 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -13695,7 +13695,7 @@ xref_basetypes (tree ref, tree base_list)
 
   binfo = make_tree_binfo (max_bases);
 
-  TYPE_BINFO (ref) = binfo;
+  SET_TYPE_BINFO (ref, binfo);
   BINFO_OFFSET (binfo) = size_zero_node;
   BINFO_TYPE (binfo) = ref;
 
diff --git a/gcc/ipa-devirt.c b/gcc/ipa-devirt.c
index f03c7f099f73..6120c362dc74 100644
--- a/gcc/ipa-devirt.c
+++ b/gcc/ipa-devirt.c
@@ -651,7 +651,7 @@ set_type_binfo (tree type, tree binfo)
 {
   for (; type; type = TYPE_NEXT_VARIANT (type))
     if (COMPLETE_TYPE_P (type))
-      TYPE_BINFO (type) = binfo;
+      SET_TYPE_BINFO (type, binfo);
     else
       gcc_assert (!TYPE_BINFO (type));
 }
diff --git a/gcc/objc/objc-act.c b/gcc/objc/objc-act.c
index 765192c82aaa..f017435dd681 100644
--- a/gcc/objc/objc-act.c
+++ b/gcc/objc/objc-act.c
@@ -2694,13 +2694,13 @@ objc_xref_basetypes (tree ref, tree basetype)
 {
   tree variant;
   tree binfo = make_tree_binfo (basetype ? 1 : 0);
-  TYPE_BINFO (ref) = binfo;
+  SET_TYPE_BINFO (ref, binfo);
   BINFO_OFFSET (binfo) = size_zero_node;
   BINFO_TYPE (binfo) = ref;
 
   gcc_assert (TYPE_MAIN_VARIANT (ref) == ref);
   for (variant = ref; variant; variant = TYPE_NEXT_VARIANT (variant))
-    TYPE_BINFO (variant) = binfo;
+    SET_TYPE_BINFO (variant, binfo);
 
   if (basetype)
     {
diff --git a/gcc/tree.c b/gcc/tree.c
index 28e157f5fd28..9634f0b72171 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -4966,7 +4966,7 @@ free_lang_data_in_type (tree type)
 	      && ((!BINFO_N_BASE_BINFOS (TYPE_BINFO (type))
 		   && !BINFO_VTABLE (TYPE_BINFO (type)))
 		  || debug_info_level != DINFO_LEVEL_NONE))
-	    TYPE_BINFO (type) = NULL;
+	    RESET_TYPE_BINFO (type);
 	}
     }
   else if (INTEGRAL_TYPE_P (type)
@@ -12006,7 +12006,7 @@ virtual_method_call_p (const_tree target)
   /* If we do not have BINFO associated, it means that type was built
      without devirtualization enabled.  Do not consider this a virtual
      call.  */
-  if (!TYPE_BINFO (obj_type_ref_class (target)))
+  if (!TYPE_BINFO_EVER_SET (obj_type_ref_class (target)))
     return false;
   return true;
 }
diff --git a/gcc/tree.h b/gcc/tree.h
index 277aa919780e..c2c130e00dbc 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -2120,7 +2120,29 @@ extern machine_mode vector_type_mode (const_tree);
 #define TYPE_MAX_VALUE_RAW(NODE) (TYPE_CHECK (NODE)->type_non_common.maxval)
 /* For record and union types, information about this type, as a base type
    for itself.  */
-#define TYPE_BINFO(NODE) (RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval)
+#define TYPE_BINFO(NODE) \
+  (RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval			\
+   && (TREE_CODE (RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval)	\
+       == TREE_BINFO)							\
+   ? RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval		\
+   : NULL_TREE)
+/* We want TYPE_BINFO to remember, with TYPE_BINFO_EVER_SET, whether
+   it was ever set, so don't allow it to be set to NULL_TREE once it
+   gets an actual value.  If it was ever set and it's to be cleared,
+   use RESET_TYPE_BINFO, to make it point to the type itself (or
+   anything, really, but pointing to the type itself doesn't stop
+   garbage collection).  */
+#define TYPE_BINFO_EVER_SET(NODE) \
+  (!!RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval)
+#define SET_TYPE_BINFO(NODE,BINFO) \
+  (!RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval || (BINFO)	\
+   ? (NODE)->type_non_common.maxval = (BINFO)				\
+   : (NODE)->type_non_common.maxval == (BINFO)				\
+   ? (BINFO) : (gcc_unreachable (), (BINFO)))
+#define RESET_TYPE_BINFO(NODE) \
+  (RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval			\
+   ? RECORD_OR_UNION_CHECK (NODE)->type_non_common.maxval = (NODE)	\
+   : NULL_TREE)
 
 /* For types, used in a language-dependent way.  */
 #define TYPE_LANG_SLOT_1(NODE) \



introduce TDF_compare_debug, omit OBJ_TYPE_REF casts with it

for  gcc/ChangeLog

	* dumpfile.h (TDF_COMPARE_DEBUG): New.
	* final.c (rest_of_clean_state): Set it for the
	-fcompare-debug dump.
	* tree-pretty-print.c (dump_generic_node): Omit OBJ_TYPE_REF
	class when TDF_COMPARE_DEBUG is set.
---
 gcc/dumpfile.h          |    1 +
 gcc/final.c             |    2 +-
 gcc/tree-pretty-print.c |   10 +++++++++-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/gcc/dumpfile.h b/gcc/dumpfile.h
index 4d9f6b3656a6..1b4d7e7dab71 100644
--- a/gcc/dumpfile.h
+++ b/gcc/dumpfile.h
@@ -93,6 +93,7 @@ enum dump_kind
 #define MSG_NOTE		 (1 << 24)  /* general optimization info */
 #define MSG_ALL		(MSG_OPTIMIZED_LOCATIONS | MSG_MISSED_OPTIMIZATION \
 			 | MSG_NOTE)
+#define TDF_COMPARE_DEBUG (1 << 25)	/* Dumping for -fcompare-debug.  */
 
 
 /* Value of TDF_NONE is used just for bits filtered by TDF_KIND_MASK.  */
diff --git a/gcc/final.c b/gcc/final.c
index 039c37a31352..fe35a36dbbf2 100644
--- a/gcc/final.c
+++ b/gcc/final.c
@@ -4629,7 +4629,7 @@ rest_of_clean_state (void)
 	{
 	  flag_dump_noaddr = flag_dump_unnumbered = 1;
 	  if (flag_compare_debug_opt || flag_compare_debug)
-	    dump_flags |= TDF_NOUID;
+	    dump_flags |= TDF_NOUID | TDF_COMPARE_DEBUG;
 	  dump_function_header (final_output, current_function_decl,
 				dump_flags);
 	  final_insns_dump_p = true;
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index 61a28c6757fb..80d45f96d67c 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -2760,7 +2760,15 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
       pp_string (pp, "OBJ_TYPE_REF(");
       dump_generic_node (pp, OBJ_TYPE_REF_EXPR (node), spc, flags, false);
       pp_semicolon (pp);
-      if (!(flags & TDF_SLIM) && virtual_method_call_p (node))
+      /* We omit the class type for -fcompare-debug because we may
+	 drop TYPE_BINFO early depending on debug info, and then
+	 virtual_method_call_p would return false, whereas when
+	 TYPE_BINFO is preserved it may still return true and then
+	 we'd print the class type.  Compare tree and rtl dumps for
+	 libstdc++-prettyprinters/shared_ptr.cc with and without -g,
+	 for example, at occurrences of OBJ_TYPE_REF.  */
+      if (!(flags & (TDF_SLIM | TDF_COMPARE_DEBUG))
+	  && virtual_method_call_p (node))
 	{
 	  pp_string (pp, "(");
 	  dump_generic_node (pp, obj_type_ref_class (node), spc, flags, false);




-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer