my switch statement disappears after the return from plugin

[Jeff Saremi <jeffsaremi@xxxxxxxxx>]

so i'm working at the cfg level. I create a new block. Redirect blocks. Introduce a new switch statement and insert it in the new block.
Before exiting from the my plugin, i print out all stmts from all blocks and my switch is seemingly there too. However at the end of my compilation it's been removed and goes with it a whole bunch of other blocks and their stmts.

Could someone tell me what am i missing in the process of adding this switch?

gimple_seq new_bb_seq = bb_seq(new_bb);
stmt = gimple_build_assign(switch_index, build_int_cst(NULL, 0));
gimple_seq_add_stmt(&new_bb_seq, stmt);
switch_stmt = gimple_build_switch_vec(switch_index, default_label, new_case_labels);
gimple_seq_add_stmt(&new_bb_seq, switch_stmt);

and this is how i build up my new case labels:

case_label = build3(CASE_LABEL_EXPR, void_type_node,
                build_int_cst(NULL, i), NULL,
                gimple_block_label(bb));
VEC_quick_push(tree, new_case_labels, case_label);

and the switch variable and its index are built this way:

new_bb = create_empty_bb(ENTRY_BLOCK_PTR);
new_bb_label = gimple_block_label (new_bb);
new_case_labels = VEC_alloc (tree, heap, block_count);
default_label = build3(CASE_LABEL_EXPR, void_type_node,
            NULL_TREE, NULL_TREE,
            create_artificial_label(UNKNOWN_LOCATION));
switch_index = create_tmp_var(integer_type_node, "sw_");

and at the end, i sandwich this block between entry and exit like this:

redirect_edge_succ(single_succ_edge(ENTRY_BLOCK_PTR), new_bb);
make_edge(new_bb, EXIT_BLOCK_PTR, EDGE_FALLTHRU);

and if print the stmts in the new block as shown in the following, I see the listing at the bottom:
for (gsi = gsi_start_bb(new_bb); !gsi_end_p(gsi); gsi_next(&gsi))
{
    gimple stmt = gsi_stmt(gsi);
    print_gimple_stmt(stdout, stmt, 8, 0);
}

********* stmts in the new block   ********
<L4>:
sw_.1 = 2;
switch (sw_.1) <default: <D.1973>, case 2: <L5>, case 3: <L6>, case 4: <L7>, case 5: L1>


The following is taken from the veclower dump:
<L3>:
  sw_.0 = 2;
  goto <bb 1>;

The switch stmt is either gone or not shown. regardless, cleanup_cfg shows the following results:
Removing basic block 9
Removing basic block 8
Removing basic block 7
Removing basic block 6
Removing basic block 5
Removing basic block 4
Removing basic block 3
f ()
{
  int sw_.1;
  int j;
  int i;
  int D.1970;

<L4>:
  sw_.1 = 2;

}