re PR middle-end/71002 (-fstrict-aliasing breaks Boost's short string optimization implementation)

2016-06-29  Richard Biener  <rguenther@suse.de>

	PR middle-end/71002
	* alias.c (component_uses_parent_alias_set_from): Handle
	type punning through union accesses by using the union alias set.
	* gimple.c (gimple_get_alias_set): Remove union type punning case.

	c-family/
	* c-common.c (c_common_get_alias_set): Remove union type punning case.
	
	fortran/
	* f95-lang.c (LANG_HOOKS_GET_ALIAS_SET): Remove (un-)define.
	(gfc_get_alias_set): Remove.

	* g++.dg/torture/pr71002.C: Adjust testcase.

From-SVN: r237839

gcc/ChangeLog

+2016-06-29  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/71002
+	* alias.c (component_uses_parent_alias_set_from): Handle
+	type punning through union accesses by using the union alias set.
+	* gimple.c (gimple_get_alias_set): Remove union type punning case.
+
 2016-07-29  Richard Biener  <rguenther@suse.de>
 
 	* match.pd ((T)(T2)x -> (T)x): Remove restriction on final

gcc/alias.c

@@ -619,6 +619,14 @@ component_uses_parent_alias_set_from (const_tree t)
 	case COMPONENT_REF:
 	  if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
 	    found = t;
+	  /* Permit type-punning when accessing a union, provided the access
+	     is directly through the union.  For example, this code does not
+	     permit taking the address of a union member and then storing
+	     through it.  Even the type-punning allowed here is a GCC
+	     extension, albeit a common and useful one; the C standard says
+	     that such accesses have implementation-defined behavior.  */
+	  else if (TREE_CODE (TREE_TYPE (TREE_OPERAND (t, 0))) == UNION_TYPE)
+	    found = t;
 	  break;
 
 	case ARRAY_REF:

gcc/c-family/ChangeLog

+2016-06-29  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/71002
+	* c-common.c (c_common_get_alias_set): Remove union type punning case.
+
 2016-06-24  Jason Merrill  <jason@redhat.com>
 
 	P0145R2: Refining Expression Order for C++.

gcc/c-family/c-common.c

@@ -4736,8 +4736,6 @@ static GTY(()) hash_table<c_type_hasher> *type_hash_table;
 alias_set_type
 c_common_get_alias_set (tree t)
 {
-  tree u;
-
   /* For VLAs, use the alias set of the element type rather than the
      default of alias set 0 for types compared structurally.  */
   if (TYPE_P (t) && TYPE_STRUCTURAL_EQUALITY_P (t))
@@ -4747,19 +4745,6 @@ c_common_get_alias_set (tree t)
       return -1;
     }
 
-  /* Permit type-punning when accessing a union, provided the access
-     is directly through the union.  For example, this code does not
-     permit taking the address of a union member and then storing
-     through it.  Even the type-punning allowed here is a GCC
-     extension, albeit a common and useful one; the C standard says
-     that such accesses have implementation-defined behavior.  */
-  for (u = t;
-       TREE_CODE (u) == COMPONENT_REF || TREE_CODE (u) == ARRAY_REF;
-       u = TREE_OPERAND (u, 0))
-    if (TREE_CODE (u) == COMPONENT_REF
-	&& TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE)
-      return 0;
-
   /* That's all the expressions we handle specially.  */
   if (!TYPE_P (t))
     return -1;

gcc/fortran/ChangeLog

+2016-06-29  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/71002
+	* f95-lang.c (LANG_HOOKS_GET_ALIAS_SET): Remove (un-)define.
+	(gfc_get_alias_set): Remove.
+
 2016-06-25  Jerry DeLisle  <jvdelisle@gcc.gnu.org>
 
 	PR fortran/71649

gcc/fortran/f95-lang.c

@@ -74,7 +74,6 @@ static bool global_bindings_p (void);
 static bool gfc_init (void);
 static void gfc_finish (void);
 static void gfc_be_parse_file (void);
-static alias_set_type gfc_get_alias_set (tree);
 static void gfc_init_ts (void);
 static tree gfc_builtin_function (tree);
 
@@ -110,7 +109,6 @@ static const struct attribute_spec gfc_attribute_table[] =
 #undef LANG_HOOKS_MARK_ADDRESSABLE
 #undef LANG_HOOKS_TYPE_FOR_MODE
 #undef LANG_HOOKS_TYPE_FOR_SIZE
-#undef LANG_HOOKS_GET_ALIAS_SET
 #undef LANG_HOOKS_INIT_TS
 #undef LANG_HOOKS_OMP_PRIVATIZE_BY_REFERENCE
 #undef LANG_HOOKS_OMP_PREDETERMINED_SHARING
@@ -142,7 +140,6 @@ static const struct attribute_spec gfc_attribute_table[] =
 #define LANG_HOOKS_PARSE_FILE           gfc_be_parse_file
 #define LANG_HOOKS_TYPE_FOR_MODE	gfc_type_for_mode
 #define LANG_HOOKS_TYPE_FOR_SIZE	gfc_type_for_size
-#define LANG_HOOKS_GET_ALIAS_SET	gfc_get_alias_set
 #define LANG_HOOKS_INIT_TS		gfc_init_ts
 #define LANG_HOOKS_OMP_PRIVATIZE_BY_REFERENCE	gfc_omp_privatize_by_reference
 #define LANG_HOOKS_OMP_PREDETERMINED_SHARING	gfc_omp_predetermined_sharing
@@ -503,24 +500,6 @@ gfc_init_decl_processing (void)
 }
 
 
-/* Return the typed-based alias set for T, which may be an expression
-   or a type.  Return -1 if we don't do anything special.  */
-
-static alias_set_type
-gfc_get_alias_set (tree t)
-{
-  tree u;
-
-  /* Permit type-punning when accessing an EQUIVALENCEd variable or
-     mixed type entry master's return value.  */
-  for (u = t; handled_component_p (u); u = TREE_OPERAND (u, 0))
-    if (TREE_CODE (u) == COMPONENT_REF
-	&& TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE)
-      return 0;
-
-  return -1;
-}
-
 /* Builtin function initialization.  */
 
 static tree

gcc/gimple.c

@@ -2400,21 +2400,6 @@ gimple_signed_type (tree type)
 alias_set_type
 gimple_get_alias_set (tree t)
 {
-  tree u;
-
-  /* Permit type-punning when accessing a union, provided the access
-     is directly through the union.  For example, this code does not
-     permit taking the address of a union member and then storing
-     through it.  Even the type-punning allowed here is a GCC
-     extension, albeit a common and useful one; the C standard says
-     that such accesses have implementation-defined behavior.  */
-  for (u = t;
-       TREE_CODE (u) == COMPONENT_REF || TREE_CODE (u) == ARRAY_REF;
-       u = TREE_OPERAND (u, 0))
-    if (TREE_CODE (u) == COMPONENT_REF
-	&& TREE_CODE (TREE_TYPE (TREE_OPERAND (u, 0))) == UNION_TYPE)
-      return 0;
-
   /* That's all the expressions we handle specially.  */
   if (!TYPE_P (t))
     return -1;

gcc/testsuite/ChangeLog

+2016-06-29  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/71002
+	* g++.dg/torture/pr71002.C: Adjust testcase.
+
 2016-06-29  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/71685

gcc/testsuite/g++.dg/torture/pr71002.C

@@ -16,11 +16,6 @@ struct long_t
   char* pointer;
 };
 
-union long_raw_t {
-  unsigned char data[sizeof(long_t)];
-  struct __attribute__((aligned(alignof(long_t)))) { } align;
-};
-
 struct short_header
 {
   unsigned char is_short : 1;
@@ -35,20 +30,20 @@ struct short_t
 
 union repr_t
 {
-  long_raw_t  r;
+  long_t      r;
   short_t     s;
 
   const short_t& short_repr() const
   { return s; }
 
   const long_t& long_repr() const
-  { return *static_cast<const long_t*>(static_cast<const void*>(&r)); }
+  { return r; }
 
   short_t& short_repr()
   { return s;  }
 
   long_t& long_repr()
-  { return *static_cast<long_t*>(static_cast<void*>(&r)); }
+  { return r; }
 };
 
 class string