+/* TAKEN_EDGE represents the an edge taken as a result of jump threading.
+ See if we can thread around TAKEN_EDGE->dest as well. If so, return
+ the edge out of TAKEN_EDGE->dest that we can statically compute will be
+ traversed.
+
+ We are much more restrictive as to the contents of TAKEN_EDGE->dest
+ as the path isolation code in tree-ssa-threadupdate.c isn't prepared
+ to handle copying intermediate blocks on a threaded path.
+
+ Long term a more consistent and structured approach to path isolation
+ would be a huge help. */
+static edge
+thread_around_empty_block (edge taken_edge,
+ gimple dummy_cond,
+ bool handle_dominating_asserts,
+ tree (*simplify) (gimple, gimple),
+ bitmap visited)
+{
+ basic_block bb = taken_edge->dest;
+ gimple_stmt_iterator gsi;
+ gimple stmt;
+ tree cond;
+
+ /* This block must have a single predecessor (E->dest). */
+ if (!single_pred_p (bb))
+ return NULL;
+
+ /* This block must have more than one successor. */
+ if (single_succ_p (bb))
+ return NULL;
+
+ /* This block can have no PHI nodes. This is overly conservative. */
+ if (!gsi_end_p (gsi_start_phis (bb)))
+ return NULL;
+
+ /* Skip over DEBUG statements at the start of the block. */
+ gsi = gsi_start_nondebug_bb (bb);
+
+ if (gsi_end_p (gsi))
+ return NULL;
+
+ /* This block can have no statements other than its control altering
+ statement. This is overly conservative. */
+ stmt = gsi_stmt (gsi);
+ if (gimple_code (stmt) != GIMPLE_COND
+ && gimple_code (stmt) != GIMPLE_GOTO
+ && gimple_code (stmt) != GIMPLE_SWITCH)
+ return NULL;
+
+ /* Extract and simplify the condition. */
+ cond = simplify_control_stmt_condition (taken_edge, stmt, dummy_cond,
+ simplify, handle_dominating_asserts);
+
+ /* If the condition can be statically computed and we have not already
+ visited the destination edge, then add the taken edge to our thread
+ path. */
+ if (cond && is_gimple_min_invariant (cond))
+ {
+ edge taken_edge = find_taken_edge (bb, cond);
+
+ if (bitmap_bit_p (visited, taken_edge->dest->index))
+ return NULL;
+ bitmap_set_bit (visited, taken_edge->dest->index);
+ return taken_edge;
+ }
+
+ return NULL;
+}
+
+/* E1 and E2 are edges into the same basic block. Return TRUE if the
+ PHI arguments associated with those edges are equal or there are no
+ PHI arguments, otherwise return FALSE. */
+
+static bool
+phi_args_equal_on_edges (edge e1, edge e2)
+{
+ gimple_stmt_iterator gsi;
+ int indx1 = e1->dest_idx;
+ int indx2 = e2->dest_idx;
+
+ for (gsi = gsi_start_phis (e1->dest); !gsi_end_p (gsi); gsi_next (&gsi))
+ {
+ gimple phi = gsi_stmt (gsi);
+
+ if (!operand_equal_p (gimple_phi_arg_def (phi, indx1),
+ gimple_phi_arg_def (phi, indx2), 0))
+ return false;
+ }
+ return true;
+}
+
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