[PATCH] Fix profiledbootstrap - store-merging aliasing issue (PR bootstrap/82916)

[Jakub Jelinek]

Hi!

We want to terminate a chain if a chain with different base (or insn
outside of any chain) has a store that the current stmt might use, or
overwrite.  The functions it used didn't cover the store after store
case which in the middle-end aliasing model needs to avoid tbaa, because
the latter store might be after a placement new or might otherwise change
the dynamic object type of the object.

The following patch does that.  Bootstrapped/regtested on x86_64-linux and
i686-linux, additionally profiledbootstrapped with the configure options
Markus mentioned in the PR.  Ok for trunk?

2017-11-09  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/82916
	* gimple-ssa-store-merging.c
	(pass_store_merging::terminate_all_aliasing_chains): For
	gimple_store_p stmts also call refs_output_dependent_p.

	* gcc.dg/store_merging_2.c: Only expect 2 successful mergings instead
	of 3.
	* gcc.dg/pr82916.c: New test.

--- gcc/gimple-ssa-store-merging.c.jj	2017-11-09 15:51:08.000000000 +0100
+++ gcc/gimple-ssa-store-merging.c	2017-11-09 18:01:20.789236951 +0100
@@ -945,6 +945,7 @@ pass_store_merging::terminate_all_aliasi
   if (!gimple_vuse (stmt))
     return false;
 
+  tree store_lhs = gimple_store_p (stmt) ? gimple_get_lhs (stmt) : NULL_TREE;
   for (imm_store_chain_info *next = m_stores_head, *cur = next; cur; cur = next)
     {
       next = cur->next;
@@ -958,8 +959,10 @@ pass_store_merging::terminate_all_aliasi
       unsigned int i;
       FOR_EACH_VEC_ELT (cur->m_store_info, i, info)
 	{
-	  if (ref_maybe_used_by_stmt_p (stmt, gimple_assign_lhs (info->stmt))
-	      || stmt_may_clobber_ref_p (stmt, gimple_assign_lhs (info->stmt)))
+	  tree lhs = gimple_assign_lhs (info->stmt);
+	  if (ref_maybe_used_by_stmt_p (stmt, lhs)
+	      || stmt_may_clobber_ref_p (stmt, lhs)
+	      || (store_lhs && refs_output_dependent_p (store_lhs, lhs)))
 	    {
 	      if (dump_file && (dump_flags & TDF_DETAILS))
 		{
--- gcc/testsuite/gcc.dg/store_merging_2.c.jj	2017-11-08 16:46:19.000000000 +0100
+++ gcc/testsuite/gcc.dg/store_merging_2.c	2017-11-09 18:16:33.482344795 +0100
@@ -77,4 +77,4 @@ main (void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump-times "Merging successful" 3 "store-merging" } } */
+/* { dg-final { scan-tree-dump-times "Merging successful" 2 "store-merging" } } */
--- gcc/testsuite/gcc.dg/pr82916.c.jj	2017-11-09 18:12:40.707128841 +0100
+++ gcc/testsuite/gcc.dg/pr82916.c	2017-11-09 18:12:19.000000000 +0100
@@ -0,0 +1,47 @@
+/* PR bootstrap/82916 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-tree-dse" } */
+
+struct A { struct A *next; };
+struct C
+{
+  int *of;
+  struct C *parent, *prev, *next;
+  int depth;
+  int min;
+  struct C *min_occ;
+};
+
+__attribute__((noipa)) struct C *
+foo (int *node)
+{
+  struct A *p = __builtin_malloc (sizeof (struct C));
+  if (!p)
+    return 0;
+  p->next = 0;
+  /* Originally placement new.  */
+  struct C *nw = (struct C *)(void *)p;
+  nw->of = node;
+  nw->parent = 0;
+  nw->prev = 0;
+  nw->next = 0;
+  nw->depth = 0;
+  nw->min_occ = nw;
+  nw->min = 0;
+  return nw;
+}
+
+int
+main ()
+{
+  int o;
+  struct C *p = foo (&o);
+  if (p)
+    {
+      if (p->of != &o || p->parent || p->prev || p->next || p->depth
+	  || p->min || p->min_occ != p)
+	__builtin_abort ();
+    }
+  __builtin_free (p);
+  return 0;
+}

	Jakub