[PATCH] Fix PR62238

[Richard Biener]

I will test the following patch fixing a tree sharing issue in
PR62238 and plugging a SSA name leak.  The issue here is that
force_gimple_operand and friends modify trees in-place, injecting
SSA name uses to them.  If you end up not emitting their definitions
or and up re-using those trees in not appropriate places you'll
break things.

Fixed by unsharing the tree.

The following also plugs the SSA name leak which makes the SSA
verifier ICE become a segfault (a released SSA name leaked into
a tree used otherwise).

Richard.

2014-11-25  Richard Biener  <rguent...@suse.de>

        PR tree-optimization/62238
        * tree-predcom.c (ref_at_iteration): Unshare the expression
        before gimplifying it.
        (prepare_initializers_chain): Discard unused seq.

        * gcc.dg/torture/pr62238.c: New testcase.

Index: gcc/tree-predcom.c
===================================================================
--- gcc/tree-predcom.c  (revision 218019)
+++ gcc/tree-predcom.c  (working copy)
@@ -1402,8 +1402,8 @@ ref_at_iteration (data_reference_p dr, i
     off = size_binop (PLUS_EXPR, off,
                      size_binop (MULT_EXPR, DR_STEP (dr), ssize_int (iter)));
   tree addr = fold_build_pointer_plus (DR_BASE_ADDRESS (dr), off);
-  addr = force_gimple_operand_1 (addr, stmts, is_gimple_mem_ref_addr,
-                                NULL_TREE);
+  addr = force_gimple_operand_1 (unshare_expr (addr), stmts,
+                                is_gimple_mem_ref_addr, NULL_TREE);
   tree alias_ptr = fold_convert (reference_alias_ptr_type (DR_REF (dr)), coff);
   /* While data-ref analysis punts on bit offsets it still handles
      bitfield accesses at byte boundaries.  Cope with that.  Note that
@@ -2354,7 +2354,6 @@ prepare_initializers_chain (struct loop
   unsigned i, n = (chain->type == CT_INVARIANT) ? 1 : chain->length;
   struct data_reference *dr = get_chain_root (chain)->ref;
   tree init;
-  gimple_seq stmts;
   dref laref;
   edge entry = loop_preheader_edge (loop);
 
@@ -2378,12 +2377,17 @@ prepare_initializers_chain (struct loop
 
   for (i = 0; i < n; i++)
     {
+      gimple_seq stmts = NULL;
+
       if (chain->inits[i] != NULL_TREE)
        continue;
 
       init = ref_at_iteration (dr, (int) i - n, &stmts);
       if (!chain->all_always_accessed && tree_could_trap_p (init))
-       return false;
+       {
+         gimple_seq_discard (stmts);
+         return false;
+       }
 
       if (stmts)
        gsi_insert_seq_on_edge_immediate (entry, stmts);
Index: gcc/testsuite/gcc.dg/torture/pr62238.c
===================================================================
--- gcc/testsuite/gcc.dg/torture/pr62238.c      (revision 0)
+++ gcc/testsuite/gcc.dg/torture/pr62238.c      (working copy)
@@ -0,0 +1,30 @@
+/* { dg-do run } */
+
+int a[4], b, c, d; 
+
+int
+fn1 (int p)
+{
+  for (; d; d++)
+    {
+      unsigned int h;
+      for (h = 0; h < 3; h++)
+       {
+         if (a[c+c+h])
+           {
+             if (p)
+               break;
+             return 0;
+           }
+         b = 0;
+       }
+    }
+  return 0;
+}
+
+int
+main ()
+{
+  fn1 (0);
+  return 0;
+}