re PR middle-end/44592 (wrong code at -O3)

	PR middle-end/44592
	* gimple-fold.c (gimplify_and_update_call_from_tree): Maintain
	proper VDEF chain for intermediate stores in the sequence.

testsuite/
	PR middle-end/44592
	* gfortran.dg/pr44592.f90: New test.

From-SVN: r161496

1 files changed, 50 insertions, 4 deletions

diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index a37b4a3..8fb604d 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -1053,7 +1053,9 @@ fold_gimple_cond (gimple stmt)
    is replaced.  If the call is expected to produces a result, then it
    is replaced by an assignment of the new RHS to the result variable.
    If the result is to be ignored, then the call is replaced by a
-   GIMPLE_NOP.  */
+   GIMPLE_NOP.  A proper VDEF chain is retained by making the first
+   VUSE and the last VDEF of the whole sequence be the same as the replaced
+   statement and using new SSA names for stores in between.  */
 
 void
 gimplify_and_update_call_from_tree (gimple_stmt_iterator *si_p, tree expr)
@@ -1065,12 +1067,15 @@ gimplify_and_update_call_from_tree (gimple_stmt_iterator *si_p, tree expr)
   gimple_seq stmts = gimple_seq_alloc();
   struct gimplify_ctx gctx;
   gimple last = NULL;
+  gimple laststore = NULL;
+  tree reaching_vuse;
 
   stmt = gsi_stmt (*si_p);
 
   gcc_assert (is_gimple_call (stmt));
 
   lhs = gimple_call_lhs (stmt);
+  reaching_vuse = gimple_vuse (stmt);
 
   push_gimplify_context (&gctx);
 
@@ -1095,13 +1100,47 @@ gimplify_and_update_call_from_tree (gimple_stmt_iterator *si_p, tree expr)
       new_stmt = gsi_stmt (i);
       find_new_referenced_vars (new_stmt);
       mark_symbols_for_renaming (new_stmt);
+      /* If the new statement has a VUSE, update it with exact SSA name we
+         know will reach this one.  */
+      if (gimple_vuse (new_stmt))
+	{
+	  /* If we've also seen a previous store create a new VDEF for
+	     the latter one, and make that the new reaching VUSE.  */
+	  if (laststore)
+	    {
+	      reaching_vuse = make_ssa_name (gimple_vop (cfun), laststore);
+	      gimple_set_vdef (laststore, reaching_vuse);
+	      update_stmt (laststore);
+	      laststore = NULL;
+	    }
+	  gimple_set_vuse (new_stmt, reaching_vuse);
+	  gimple_set_modified (new_stmt, true);
+	}
+      if (gimple_assign_single_p (new_stmt)
+	  && !is_gimple_reg (gimple_assign_lhs (new_stmt)))
+	{
+	  laststore = new_stmt;
+	}
       last = new_stmt;
     }
 
   if (lhs == NULL_TREE)
     {
-      unlink_stmt_vdef (stmt);
-      release_defs (stmt);
+      /* If we replace a call without LHS that has a VDEF and our new
+         sequence ends with a store we must make that store have the same
+	 vdef in order not to break the sequencing.  This can happen
+	 for instance when folding memcpy calls into assignments.  */
+      if (gimple_vdef (stmt) && laststore)
+	{
+	  gimple_set_vdef (laststore, gimple_vdef (stmt));
+	  move_ssa_defining_stmt_for_defs (laststore, stmt);
+	  update_stmt (laststore);
+	}
+      else
+	{
+	  unlink_stmt_vdef (stmt);
+	  release_defs (stmt);
+	}
       new_stmt = last;
     }
   else
@@ -1111,8 +1150,15 @@ gimplify_and_update_call_from_tree (gimple_stmt_iterator *si_p, tree expr)
 	  gsi_insert_before (si_p, last, GSI_NEW_STMT);
 	  gsi_next (si_p);
 	}
+      if (laststore)
+	{
+	  reaching_vuse = make_ssa_name (gimple_vop (cfun), laststore);
+	  gimple_set_vdef (laststore, reaching_vuse);
+	  update_stmt (laststore);
+	  laststore = NULL;
+	}
       new_stmt = gimple_build_assign (lhs, tmp);
-      gimple_set_vuse (new_stmt, gimple_vuse (stmt));
+      gimple_set_vuse (new_stmt, reaching_vuse);
       gimple_set_vdef (new_stmt, gimple_vdef (stmt));
       move_ssa_defining_stmt_for_defs (new_stmt, stmt);
     }