-/* Return true if basic block BB does nothing except pass control
- flow to another block and that we can safely insert a label at
- the start of the successor block.
-
- As a precondition, we require that BB be not equal to
- ENTRY_BLOCK_PTR. */
-
-static bool
-tree_forwarder_block_p (basic_block bb, bool phi_wanted)
-{
- block_stmt_iterator bsi;
-
- /* BB must have a single outgoing edge. */
- if (single_succ_p (bb) != 1
- /* If PHI_WANTED is false, BB must not have any PHI nodes.
- Otherwise, BB must have PHI nodes. */
- || (phi_nodes (bb) != NULL_TREE) != phi_wanted
- /* BB may not be a predecessor of EXIT_BLOCK_PTR. */
- || single_succ (bb) == EXIT_BLOCK_PTR
- /* Nor should this be an infinite loop. */
- || single_succ (bb) == bb
- /* BB may not have an abnormal outgoing edge. */
- || (single_succ_edge (bb)->flags & EDGE_ABNORMAL))
- return false;
-
-#if ENABLE_CHECKING
- gcc_assert (bb != ENTRY_BLOCK_PTR);
-#endif
-
- /* Now walk through the statements backward. We can ignore labels,
- anything else means this is not a forwarder block. */
- for (bsi = bsi_last (bb); !bsi_end_p (bsi); bsi_next (&bsi))
- {
- tree stmt = bsi_stmt (bsi);
-
- switch (TREE_CODE (stmt))
- {
- case LABEL_EXPR:
- if (DECL_NONLOCAL (LABEL_EXPR_LABEL (stmt)))
- return false;
- break;
-
- default:
- return false;
- }
- }
-
- if (find_edge (ENTRY_BLOCK_PTR, bb))
- return false;
-
- if (current_loops)
- {
- basic_block dest;
- /* Protect loop latches, headers and preheaders. */
- if (bb->loop_father->header == bb)
- return false;
- dest = EDGE_SUCC (bb, 0)->dest;
-
- if (dest->loop_father->header == dest)
- return false;
- }
-
- return true;
-}
-
-/* Return true if BB has at least one abnormal incoming edge. */
-
-static inline bool
-has_abnormal_incoming_edge_p (basic_block bb)
-{
- edge e;
- edge_iterator ei;
-
- FOR_EACH_EDGE (e, ei, bb->preds)
- if (e->flags & EDGE_ABNORMAL)
- return true;
-
- return false;
-}
-
-/* Removes forwarder block BB. Returns false if this failed. If a new
- forwarder block is created due to redirection of edges, it is
- stored to worklist. */
-
-static bool
-remove_forwarder_block (basic_block bb, basic_block **worklist)
-{
- edge succ = single_succ_edge (bb), e, s;
- basic_block dest = succ->dest;
- tree label;
- tree phi;
- edge_iterator ei;
- block_stmt_iterator bsi, bsi_to;
- bool seen_abnormal_edge = false;
-
- /* We check for infinite loops already in tree_forwarder_block_p.
- However it may happen that the infinite loop is created
- afterwards due to removal of forwarders. */
- if (dest == bb)
- return false;
-
- /* If the destination block consists of a nonlocal label, do not merge
- it. */
- label = first_stmt (dest);
- if (label
- && TREE_CODE (label) == LABEL_EXPR
- && DECL_NONLOCAL (LABEL_EXPR_LABEL (label)))
- return false;
-
- /* If there is an abnormal edge to basic block BB, but not into
- dest, problems might occur during removal of the phi node at out
- of ssa due to overlapping live ranges of registers.
-
- If there is an abnormal edge in DEST, the problems would occur
- anyway since cleanup_dead_labels would then merge the labels for
- two different eh regions, and rest of exception handling code
- does not like it.
-
- So if there is an abnormal edge to BB, proceed only if there is
- no abnormal edge to DEST and there are no phi nodes in DEST. */
- if (has_abnormal_incoming_edge_p (bb))
- {
- seen_abnormal_edge = true;
-
- if (has_abnormal_incoming_edge_p (dest)
- || phi_nodes (dest) != NULL_TREE)
- return false;
- }
-
- /* If there are phi nodes in DEST, and some of the blocks that are
- predecessors of BB are also predecessors of DEST, check that the
- phi node arguments match. */
- if (phi_nodes (dest))
- {
- FOR_EACH_EDGE (e, ei, bb->preds)
- {
- s = find_edge (e->src, dest);
- if (!s)
- continue;
-
- if (!phi_alternatives_equal (dest, succ, s))
- return false;
- }
- }
-
- /* Redirect the edges. */
- for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
- {
- if (e->flags & EDGE_ABNORMAL)
- {
- /* If there is an abnormal edge, redirect it anyway, and
- move the labels to the new block to make it legal. */
- s = redirect_edge_succ_nodup (e, dest);
- }
- else
- s = redirect_edge_and_branch (e, dest);
-
- if (s == e)
- {
- /* Create arguments for the phi nodes, since the edge was not
- here before. */
- for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
- add_phi_arg (phi, PHI_ARG_DEF (phi, succ->dest_idx), s);
- }
- else
- {
- /* The source basic block might become a forwarder. We know
- that it was not a forwarder before, since it used to have
- at least two outgoing edges, so we may just add it to
- worklist. */
- if (tree_forwarder_block_p (s->src, false))
- *(*worklist)++ = s->src;
- }
- }
-
- if (seen_abnormal_edge)
- {
- /* Move the labels to the new block, so that the redirection of
- the abnormal edges works. */
-
- bsi_to = bsi_start (dest);
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
- {
- label = bsi_stmt (bsi);
- gcc_assert (TREE_CODE (label) == LABEL_EXPR);
- bsi_remove (&bsi);
- bsi_insert_before (&bsi_to, label, BSI_CONTINUE_LINKING);
- }
- }
-
- /* Update the dominators. */
- if (dom_info_available_p (CDI_DOMINATORS))
- {
- basic_block dom, dombb, domdest;
-
- dombb = get_immediate_dominator (CDI_DOMINATORS, bb);
- domdest = get_immediate_dominator (CDI_DOMINATORS, dest);
- if (domdest == bb)
- {
- /* Shortcut to avoid calling (relatively expensive)
- nearest_common_dominator unless necessary. */
- dom = dombb;
- }
- else
- dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb);
-
- set_immediate_dominator (CDI_DOMINATORS, dest, dom);
- }
-
- /* And kill the forwarder block. */
- delete_basic_block (bb);
-
- return true;
-}
-
-/* Removes forwarder blocks. */
-
-static bool
-cleanup_forwarder_blocks (void)
-{
- basic_block bb;
- bool changed = false;
- basic_block *worklist = xmalloc (sizeof (basic_block) * n_basic_blocks);
- basic_block *current = worklist;
-
- FOR_EACH_BB (bb)
- {
- if (tree_forwarder_block_p (bb, false))
- *current++ = bb;
- }
-
- while (current != worklist)
- {
- bb = *--current;
- changed |= remove_forwarder_block (bb, ¤t);
- }
-
- free (worklist);
- return changed;
-}
-
-/* Merge the PHI nodes at BB into those at BB's sole successor. */
-
-static void
-remove_forwarder_block_with_phi (basic_block bb)
-{
- edge succ = single_succ_edge (bb);
- basic_block dest = succ->dest;
- tree label;
- basic_block dombb, domdest, dom;
-
- /* We check for infinite loops already in tree_forwarder_block_p.
- However it may happen that the infinite loop is created
- afterwards due to removal of forwarders. */
- if (dest == bb)
- return;
-
- /* If the destination block consists of a nonlocal label, do not
- merge it. */
- label = first_stmt (dest);
- if (label
- && TREE_CODE (label) == LABEL_EXPR
- && DECL_NONLOCAL (LABEL_EXPR_LABEL (label)))
- return;
-
- /* Redirect each incoming edge to BB to DEST. */
- while (EDGE_COUNT (bb->preds) > 0)
- {
- edge e = EDGE_PRED (bb, 0), s;
- tree phi;
-
- s = find_edge (e->src, dest);
- if (s)
- {
- /* We already have an edge S from E->src to DEST. If S and
- E->dest's sole successor edge have the same PHI arguments
- at DEST, redirect S to DEST. */
- if (phi_alternatives_equal (dest, s, succ))
- {
- e = redirect_edge_and_branch (e, dest);
- PENDING_STMT (e) = NULL_TREE;
- continue;
- }
-
- /* PHI arguments are different. Create a forwarder block by
- splitting E so that we can merge PHI arguments on E to
- DEST. */
- e = single_succ_edge (split_edge (e));
- }
-
- s = redirect_edge_and_branch (e, dest);
-
- /* redirect_edge_and_branch must not create a new edge. */
- gcc_assert (s == e);
-
- /* Add to the PHI nodes at DEST each PHI argument removed at the
- destination of E. */
- for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
- {
- tree def = PHI_ARG_DEF (phi, succ->dest_idx);
-
- if (TREE_CODE (def) == SSA_NAME)
- {
- tree var;
-
- /* If DEF is one of the results of PHI nodes removed during
- redirection, replace it with the PHI argument that used
- to be on E. */
- for (var = PENDING_STMT (e); var; var = TREE_CHAIN (var))
- {
- tree old_arg = TREE_PURPOSE (var);
- tree new_arg = TREE_VALUE (var);
-
- if (def == old_arg)
- {
- def = new_arg;
- break;
- }
- }
- }
-
- add_phi_arg (phi, def, s);
- }
-
- PENDING_STMT (e) = NULL;
- }
-
- /* Update the dominators. */
- dombb = get_immediate_dominator (CDI_DOMINATORS, bb);
- domdest = get_immediate_dominator (CDI_DOMINATORS, dest);
- if (domdest == bb)
- {
- /* Shortcut to avoid calling (relatively expensive)
- nearest_common_dominator unless necessary. */
- dom = dombb;
- }
- else
- dom = nearest_common_dominator (CDI_DOMINATORS, domdest, dombb);
-
- set_immediate_dominator (CDI_DOMINATORS, dest, dom);
-
- /* Remove BB since all of BB's incoming edges have been redirected
- to DEST. */
- delete_basic_block (bb);
-}
-
-/* This pass merges PHI nodes if one feeds into another. For example,
- suppose we have the following:
-
- goto <bb 9> (<L9>);
-
-<L8>:;
- tem_17 = foo ();
-
- # tem_6 = PHI <tem_17(8), tem_23(7)>;
-<L9>:;
-
- # tem_3 = PHI <tem_6(9), tem_2(5)>;
-<L10>:;
-
- Then we merge the first PHI node into the second one like so:
-
- goto <bb 9> (<L10>);
-
-<L8>:;
- tem_17 = foo ();
-
- # tem_3 = PHI <tem_23(7), tem_2(5), tem_17(8)>;
-<L10>:;
-*/
-
-static void
-merge_phi_nodes (void)
-{
- basic_block *worklist = xmalloc (sizeof (basic_block) * n_basic_blocks);
- basic_block *current = worklist;
- basic_block bb;
-
- calculate_dominance_info (CDI_DOMINATORS);
-
- /* Find all PHI nodes that we may be able to merge. */
- FOR_EACH_BB (bb)
- {
- basic_block dest;
-
- /* Look for a forwarder block with PHI nodes. */
- if (!tree_forwarder_block_p (bb, true))
- continue;
-
- dest = single_succ (bb);
-
- /* We have to feed into another basic block with PHI
- nodes. */
- if (!phi_nodes (dest)
- /* We don't want to deal with a basic block with
- abnormal edges. */
- || has_abnormal_incoming_edge_p (bb))
- continue;
-
- if (!dominated_by_p (CDI_DOMINATORS, dest, bb))
- {
- /* If BB does not dominate DEST, then the PHI nodes at
- DEST must be the only users of the results of the PHI
- nodes at BB. */
- *current++ = bb;
- }
- }
-
- /* Now let's drain WORKLIST. */
- while (current != worklist)
- {
- bb = *--current;
- remove_forwarder_block_with_phi (bb);
- }
-
- free (worklist);
-}
-
-static bool
-gate_merge_phi (void)
-{
- return 1;
-}
-
-struct tree_opt_pass pass_merge_phi = {
- "mergephi", /* name */
- gate_merge_phi, /* gate */
- merge_phi_nodes, /* execute */
- NULL, /* sub */
- NULL, /* next */
- 0, /* static_pass_number */
- TV_TREE_MERGE_PHI, /* tv_id */
- PROP_cfg | PROP_ssa, /* properties_required */
- 0, /* properties_provided */
- 0, /* properties_destroyed */
- 0, /* todo_flags_start */
- TODO_dump_func | TODO_ggc_collect /* todo_flags_finish */
- | TODO_verify_ssa,
- 0 /* letter */
-};
-