diff --git a/llvm/test/Regression/Transforms/LCSSA/2006-10-31-UnreachableBlock.ll b/llvm/test/Regression/Transforms/LCSSA/2006-10-31-UnreachableBlock.ll
new file mode 100644
index 000000000000..f70d5c80397f
--- /dev/null
+++ b/llvm/test/Regression/Transforms/LCSSA/2006-10-31-UnreachableBlock.ll
@@ -0,0 +1,270 @@
+; RUN: llvm-as < %s | opt -lcssa -disable-output
+; PR977
+
+void %process_backlog() {
+entry:
+	br label %loopentry.preheader
+
+loopentry.preheader:		; preds = %dead_block_after_break, %entry
+	%work.0.ph = phi int [ %inc, %dead_block_after_break ], [ 0, %entry ]		; <int> [#uses=0]
+	br label %loopentry
+
+loopentry:		; preds = %endif.1, %loopentry.preheader
+	br bool false, label %then.i, label %loopentry.__skb_dequeue67.exit_crit_edge
+
+loopentry.__skb_dequeue67.exit_crit_edge:		; preds = %loopentry
+	br label %__skb_dequeue67.exit
+
+then.i:		; preds = %loopentry
+	br label %__skb_dequeue67.exit
+
+__skb_dequeue67.exit:		; preds = %then.i, %loopentry.__skb_dequeue67.exit_crit_edge
+	br bool false, label %then.0, label %__skb_dequeue67.exit.endif.0_crit_edge
+
+__skb_dequeue67.exit.endif.0_crit_edge:		; preds = %__skb_dequeue67.exit
+	br label %endif.0
+
+then.0:		; preds = %__skb_dequeue67.exit
+	br label %job_done
+
+dead_block_after_goto:		; No predecessors!
+	unreachable
+
+endif.0:		; preds = %__skb_dequeue67.exit.endif.0_crit_edge
+	br bool false, label %then.0.i, label %endif.0.endif.0.i_crit_edge
+
+endif.0.endif.0.i_crit_edge:		; preds = %endif.0
+	br label %endif.0.i
+
+then.0.i:		; preds = %endif.0
+	br label %endif.0.i
+
+endif.0.i:		; preds = %then.0.i, %endif.0.endif.0.i_crit_edge
+	br bool false, label %then.i.i, label %endif.0.i.skb_bond.exit.i_crit_edge
+
+endif.0.i.skb_bond.exit.i_crit_edge:		; preds = %endif.0.i
+	br label %skb_bond.exit.i
+
+then.i.i:		; preds = %endif.0.i
+	br label %skb_bond.exit.i
+
+skb_bond.exit.i:		; preds = %then.i.i, %endif.0.i.skb_bond.exit.i_crit_edge
+	br label %loopentry.0.i
+
+loopentry.0.i:		; preds = %loopentry.0.i.backedge, %skb_bond.exit.i
+	br bool false, label %loopentry.0.i.no_exit.0.i_crit_edge, label %loopentry.0.i.loopexit.0.i_crit_edge
+
+loopentry.0.i.loopexit.0.i_crit_edge:		; preds = %loopentry.0.i
+	br label %loopexit.0.i
+
+loopentry.0.i.no_exit.0.i_crit_edge:		; preds = %loopentry.0.i
+	br label %no_exit.0.i
+
+no_exit.0.i:		; preds = %then.3.i.no_exit.0.i_crit_edge, %loopentry.0.i.no_exit.0.i_crit_edge
+	br bool false, label %no_exit.0.i.shortcirc_done.0.i_crit_edge, label %shortcirc_next.0.i
+
+no_exit.0.i.shortcirc_done.0.i_crit_edge:		; preds = %no_exit.0.i
+	br label %shortcirc_done.0.i
+
+shortcirc_next.0.i:		; preds = %no_exit.0.i
+	br label %shortcirc_done.0.i
+
+shortcirc_done.0.i:		; preds = %shortcirc_next.0.i, %no_exit.0.i.shortcirc_done.0.i_crit_edge
+	br bool false, label %then.1.i, label %endif.1.i
+
+then.1.i:		; preds = %shortcirc_done.0.i
+	br bool false, label %then.2.i, label %then.1.i.endif.2.i_crit_edge
+
+then.1.i.endif.2.i_crit_edge:		; preds = %then.1.i
+	br label %endif.2.i
+
+then.2.i:		; preds = %then.1.i
+	br bool false, label %then.3.i, label %else.0.i
+
+then.3.i:		; preds = %then.2.i
+	br bool false, label %then.3.i.no_exit.0.i_crit_edge, label %then.3.i.loopexit.0.i_crit_edge
+
+then.3.i.loopexit.0.i_crit_edge:		; preds = %then.3.i
+	br label %loopexit.0.i
+
+then.3.i.no_exit.0.i_crit_edge:		; preds = %then.3.i
+	br label %no_exit.0.i
+
+else.0.i:		; preds = %then.2.i
+	br label %endif.2.i
+
+endif.3.i:		; No predecessors!
+	unreachable
+
+endif.2.i:		; preds = %else.0.i, %then.1.i.endif.2.i_crit_edge
+	br label %loopentry.0.i.backedge
+
+endif.1.i:		; preds = %shortcirc_done.0.i
+	br label %loopentry.0.i.backedge
+
+loopentry.0.i.backedge:		; preds = %endif.1.i, %endif.2.i
+	br label %loopentry.0.i
+
+loopexit.0.i:		; preds = %then.3.i.loopexit.0.i_crit_edge, %loopentry.0.i.loopexit.0.i_crit_edge
+	br label %loopentry.1.i
+
+loopentry.1.i:		; preds = %loopentry.1.i.backedge, %loopexit.0.i
+	br bool false, label %loopentry.1.i.no_exit.1.i_crit_edge, label %loopentry.1.i.loopexit.1.i_crit_edge
+
+loopentry.1.i.loopexit.1.i_crit_edge:		; preds = %loopentry.1.i
+	br label %loopexit.1.i
+
+loopentry.1.i.no_exit.1.i_crit_edge:		; preds = %loopentry.1.i
+	br label %no_exit.1.i
+
+no_exit.1.i:		; preds = %then.6.i.no_exit.1.i_crit_edge, %loopentry.1.i.no_exit.1.i_crit_edge
+	br bool false, label %shortcirc_next.1.i, label %no_exit.1.i.shortcirc_done.1.i_crit_edge
+
+no_exit.1.i.shortcirc_done.1.i_crit_edge:		; preds = %no_exit.1.i
+	br label %shortcirc_done.1.i
+
+shortcirc_next.1.i:		; preds = %no_exit.1.i
+	br bool false, label %shortcirc_next.1.i.shortcirc_done.2.i_crit_edge, label %shortcirc_next.2.i
+
+shortcirc_next.1.i.shortcirc_done.2.i_crit_edge:		; preds = %shortcirc_next.1.i
+	br label %shortcirc_done.2.i
+
+shortcirc_next.2.i:		; preds = %shortcirc_next.1.i
+	br label %shortcirc_done.2.i
+
+shortcirc_done.2.i:		; preds = %shortcirc_next.2.i, %shortcirc_next.1.i.shortcirc_done.2.i_crit_edge
+	br label %shortcirc_done.1.i
+
+shortcirc_done.1.i:		; preds = %shortcirc_done.2.i, %no_exit.1.i.shortcirc_done.1.i_crit_edge
+	br bool false, label %then.4.i, label %endif.4.i
+
+then.4.i:		; preds = %shortcirc_done.1.i
+	br bool false, label %then.5.i, label %then.4.i.endif.5.i_crit_edge
+
+then.4.i.endif.5.i_crit_edge:		; preds = %then.4.i
+	br label %endif.5.i
+
+then.5.i:		; preds = %then.4.i
+	br bool false, label %then.6.i, label %else.1.i
+
+then.6.i:		; preds = %then.5.i
+	br bool false, label %then.6.i.no_exit.1.i_crit_edge, label %then.6.i.loopexit.1.i_crit_edge
+
+then.6.i.loopexit.1.i_crit_edge:		; preds = %then.6.i
+	br label %loopexit.1.i
+
+then.6.i.no_exit.1.i_crit_edge:		; preds = %then.6.i
+	br label %no_exit.1.i
+
+else.1.i:		; preds = %then.5.i
+	br label %endif.5.i
+
+endif.6.i:		; No predecessors!
+	unreachable
+
+endif.5.i:		; preds = %else.1.i, %then.4.i.endif.5.i_crit_edge
+	br label %loopentry.1.i.backedge
+
+endif.4.i:		; preds = %shortcirc_done.1.i
+	br label %loopentry.1.i.backedge
+
+loopentry.1.i.backedge:		; preds = %endif.4.i, %endif.5.i
+	br label %loopentry.1.i
+
+loopexit.1.i:		; preds = %then.6.i.loopexit.1.i_crit_edge, %loopentry.1.i.loopexit.1.i_crit_edge
+	br bool false, label %then.7.i, label %else.2.i
+
+then.7.i:		; preds = %loopexit.1.i
+	br bool false, label %then.8.i, label %else.3.i
+
+then.8.i:		; preds = %then.7.i
+	br label %netif_receive_skb.exit
+
+else.3.i:		; preds = %then.7.i
+	br label %netif_receive_skb.exit
+
+endif.8.i:		; No predecessors!
+	unreachable
+
+else.2.i:		; preds = %loopexit.1.i
+	br bool false, label %else.2.i.shortcirc_done.i.i_crit_edge, label %shortcirc_next.i.i
+
+else.2.i.shortcirc_done.i.i_crit_edge:		; preds = %else.2.i
+	br label %shortcirc_done.i.i
+
+shortcirc_next.i.i:		; preds = %else.2.i
+	br label %shortcirc_done.i.i
+
+shortcirc_done.i.i:		; preds = %shortcirc_next.i.i, %else.2.i.shortcirc_done.i.i_crit_edge
+	br bool false, label %then.i1.i, label %shortcirc_done.i.i.kfree_skb65.exit.i_crit_edge
+
+shortcirc_done.i.i.kfree_skb65.exit.i_crit_edge:		; preds = %shortcirc_done.i.i
+	br label %kfree_skb65.exit.i
+
+then.i1.i:		; preds = %shortcirc_done.i.i
+	br label %kfree_skb65.exit.i
+
+kfree_skb65.exit.i:		; preds = %then.i1.i, %shortcirc_done.i.i.kfree_skb65.exit.i_crit_edge
+	br label %netif_receive_skb.exit
+
+netif_receive_skb.exit:		; preds = %kfree_skb65.exit.i, %else.3.i, %then.8.i
+	br bool false, label %then.i1, label %netif_receive_skb.exit.dev_put69.exit_crit_edge
+
+netif_receive_skb.exit.dev_put69.exit_crit_edge:		; preds = %netif_receive_skb.exit
+	br label %dev_put69.exit
+
+then.i1:		; preds = %netif_receive_skb.exit
+	br label %dev_put69.exit
+
+dev_put69.exit:		; preds = %then.i1, %netif_receive_skb.exit.dev_put69.exit_crit_edge
+	%inc = add int 0, 1		; <int> [#uses=1]
+	br bool false, label %dev_put69.exit.shortcirc_done_crit_edge, label %shortcirc_next
+
+dev_put69.exit.shortcirc_done_crit_edge:		; preds = %dev_put69.exit
+	br label %shortcirc_done
+
+shortcirc_next:		; preds = %dev_put69.exit
+	br label %shortcirc_done
+
+shortcirc_done:		; preds = %shortcirc_next, %dev_put69.exit.shortcirc_done_crit_edge
+	br bool false, label %then.1, label %endif.1
+
+then.1:		; preds = %shortcirc_done
+	ret void
+
+dead_block_after_break:		; No predecessors!
+	br label %loopentry.preheader
+
+endif.1:		; preds = %shortcirc_done
+	br label %loopentry
+
+loopexit:		; No predecessors!
+	unreachable
+
+after_ret.0:		; No predecessors!
+	br label %job_done
+
+job_done:		; preds = %after_ret.0, %then.0
+	br label %loopentry.i
+
+loopentry.i:		; preds = %no_exit.i, %job_done
+	br bool false, label %no_exit.i, label %clear_bit62.exit
+
+no_exit.i:		; preds = %loopentry.i
+	br label %loopentry.i
+
+clear_bit62.exit:		; preds = %loopentry.i
+	br bool false, label %then.2, label %endif.2
+
+then.2:		; preds = %clear_bit62.exit
+	ret void
+
+endif.2:		; preds = %clear_bit62.exit
+	ret void
+
+after_ret.1:		; No predecessors!
+	ret void
+
+return:		; No predecessors!
+	unreachable
+}