[Bug tree-optimization/23286] missed fully redundant expression

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23286

--- Comment #38 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-02-16 12:44:31 UTC ---
Incremental patch to fix the EH related ICEs:

Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c.orig     2012-02-16 12:08:57.000000000 +0100
+++ gcc/tree-ssa-pre.c  2012-02-16 12:08:50.000000000 +0100
@@ -3937,7 +3937,8 @@ do_hoist_insertion (basic_block block AT
       find_or_generate_expression (block, expr, &stmts, NULL);

       last = gsi_last_bb (block);
-      if (gsi_end_p (last) || is_ctrl_stmt (gsi_stmt (last)))
+      if (gsi_end_p (last)
+         || stmt_ends_bb_p (gsi_stmt (last)))
        gsi_insert_seq_before (&last, stmts, GSI_SAME_STMT);
       else
        gsi_insert_seq_after (&last, stmts, GSI_SAME_STMT);

when hoisting into

  # BLOCK 19
  # PRED: 18 (fallthru,exec)
  [LP 15] D.2722_10 = CYapfBaseT::PfGetSettings (D.2723_9);
  goto <bb 20>;
  # SUCC: 20 (fallthru,exec) 113 (eh,exec)

but of course we'd have to verify we can hoist across such throwing
stmt (it might be a store clobbering what we insert),
so maybe disabling hoisting in that case would be more appropriate.
With

Index: gcc/tree-ssa-pre.c
===================================================================
--- gcc/tree-ssa-pre.c.orig     2012-02-16 12:28:04.000000000 +0100
+++ gcc/tree-ssa-pre.c  2012-02-16 12:27:37.000000000 +0100
@@ -3874,6 +3874,7 @@ do_hoist_insertion (basic_block block AT
   bitmap_iterator bi;
   bitmap_set_t hoistable_set;
   bitmap availout_in_some;
+  gimple_stmt_iterator last;

   /* At least two successors, or else...  */
   gcc_assert (EDGE_COUNT (block->succs) >= 2);
@@ -3886,6 +3887,14 @@ do_hoist_insertion (basic_block block AT
     if (! single_pred_p (e->dest))
       return false;

+  /* Determine the insertion point.  If we cannot safely insert before
+     the last stmt if we'd have to, bail out.  */
+  last = gsi_last_bb (block);
+  if (!gsi_end_p (last)
+      && !is_ctrl_stmt (gsi_stmt (last))
+      && stmt_ends_bb_p (gsi_stmt (last)))
+    return false;
+
   hoistable_set = bitmap_set_new ();
   availout_in_some = BITMAP_ALLOC (&grand_bitmap_obstack);

@@ -3916,7 +3925,6 @@ do_hoist_insertion (basic_block block AT
       pre_expr expr = expression_for_id (i);
       unsigned int value_id = get_expr_value_id (expr);
       gimple_seq stmts = NULL;
-      gimple_stmt_iterator last;

       /* If the value of this expression is not available in at least one
         successor, do not hoist the value.  */
@@ -3936,7 +3944,6 @@ do_hoist_insertion (basic_block block AT

       find_or_generate_expression (block, expr, &stmts, NULL);

-      last = gsi_last_bb (block);
       if (gsi_end_p (last) || is_ctrl_stmt (gsi_stmt (last)))
        gsi_insert_seq_before (&last, stmts, GSI_SAME_STMT);
       else

Which leaves us with

/abuild/rguenther/obj/./gcc/xgcc -B/abuild/rguenther/obj/./gcc/
-B/usr/local/x86_64-unknown-linux-gnu/bin/
-B/usr/local/x86_64-unknown-linux-gnu/lib/ -isystem
/usr/local/x86_64-unknown-linux-gnu/include -isystem
/usr/local/x86_64-unknown-linux-gnu/sys-include    -c -g -O2 -m32 -fpic  -W
-Wall -gnatpg -nostdinc -m32  a-nlrear.ads -o a-nlrear.o

raised STORAGE_ERROR : stack overflow or erroneous memory access
make[9]: *** [a-nlrear.o] Error 1

during stage3 libada build ...