/* Generic dominator tree walker
- Copyright (C) 2003, 2004, 2005, 2007 Free Software Foundation, Inc.
+ Copyright (C) 2003-2021 Free Software Foundation, Inc.
Contributed by Diego Novillo <dnovillo@redhat.com>
This file is part of GCC.
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
-typedef void *void_p;
-DEF_VEC_P(void_p);
-DEF_VEC_ALLOC_P(void_p,heap);
+#ifndef GCC_DOM_WALK_H
+#define GCC_DOM_WALK_H
-/* This is the main data structure for the dominator walker. It provides
- the callback hooks as well as a convenient place to hang block local
- data and pass-global data. */
-
-struct dom_walk_data
+/**
+ * This is the main class for the dominator walker. It is expected that
+ * consumers will have a custom class inheriting from it, which will over ride
+ * at least one of before_dom_children and after_dom_children to implement the
+ * custom behavior.
+ */
+class dom_walker
{
+public:
+ static const edge STOP;
+
+ /* An enum for determining whether the dom walk should be constrained to
+ blocks reachable by executable edges. */
+
+ enum reachability
+ {
+ /* Walk all blocks within the CFG. */
+ ALL_BLOCKS,
+
+ /* Use REACHABLE_BLOCKS when your subclass can discover that some edges
+ are not executable.
+
+ If a subclass can discover that a COND, SWITCH or GOTO has a static
+ target in the before_dom_children callback, the taken edge should
+ be returned. The generic walker will clear EDGE_EXECUTABLE on all
+ edges it can determine are not executable.
+
+ With REACHABLE_BLOCKS, EDGE_EXECUTABLE will be set on every edge in
+ the dom_walker ctor; the flag will then be cleared on edges that are
+ determined to be not executable. */
+ REACHABLE_BLOCKS,
+
+ /* Identical to REACHABLE_BLOCKS, but the initial state of EDGE_EXECUTABLE
+ will instead be preserved in the ctor, allowing for information about
+ non-executable edges to be merged in from an earlier analysis (and
+ potentially for additional edges to be marked as non-executable). */
+ REACHABLE_BLOCKS_PRESERVING_FLAGS
+ };
+
+ /* You can provide a mapping of basic-block index to RPO if you
+ have that readily available or you do multiple walks. If you
+ specify NULL as BB_INDEX_TO_RPO dominator children will not be
+ walked in RPO order. */
+ dom_walker (cdi_direction direction, enum reachability = ALL_BLOCKS,
+ int *bb_index_to_rpo = NULL);
+
+ ~dom_walker ();
+
+ /* Walk the dominator tree. */
+ void walk (basic_block);
+
+ /* Function to call before the recursive walk of the dominator children.
+
+ Return value is the always taken edge if the block has multiple outgoing
+ edges, NULL otherwise. When skipping unreachable blocks, the walker
+ uses the taken edge information to clear EDGE_EXECUTABLE on the other
+ edges, exposing unreachable blocks. A NULL return value means all
+ outgoing edges should still be considered executable. A return value
+ of STOP means to stop the domwalk from processing dominated blocks from
+ here. This can be used to process a SEME region only (note domwalk
+ will still do work linear in function size). */
+ virtual edge before_dom_children (basic_block) { return NULL; }
+
+ /* Function to call after the recursive walk of the dominator children. */
+ virtual void after_dom_children (basic_block) {}
+
+private:
/* This is the direction of the dominator tree we want to walk. i.e.,
if it is set to CDI_DOMINATORS, then we walk the dominator tree,
if it is set to CDI_POST_DOMINATORS, then we walk the post
dominator tree. */
- ENUM_BITFIELD (cdi_direction) dom_direction : 2;
-
- /* Nonzero if the statement walker should walk the statements from
- last to first within a basic block instead of first to last.
-
- Note this affects both statement walkers. We haven't yet needed
- to use the second statement walker for anything, so it's hard to
- predict if we really need the ability to select their direction
- independently. */
- BOOL_BITFIELD walk_stmts_backward : 1;
-
- /* Function to initialize block local data.
-
- Note that the dominator walker infrastructure may provide a new
- fresh, and zero'd block local data structure, or it may re-use an
- existing block local data structure.
-
- If the block local structure has items such as virtual arrays, then
- that allows your optimizer to re-use those arrays rather than
- creating new ones. */
- void (*initialize_block_local_data) (struct dom_walk_data *,
- basic_block, bool);
-
- /* Function to call before the statement walk occurring before the
- recursive walk of the dominator children.
-
- This typically initializes a block local data and pushes that
- data onto BLOCK_DATA_STACK. */
- void (*before_dom_children_before_stmts) (struct dom_walk_data *,
- basic_block);
-
- /* Function to call to walk statements before the recursive walk
- of the dominator children. */
- void (*before_dom_children_walk_stmts) (struct dom_walk_data *,
- basic_block, block_stmt_iterator);
-
- /* Function to call after the statement walk occurring before the
- recursive walk of the dominator children. */
- void (*before_dom_children_after_stmts) (struct dom_walk_data *,
- basic_block);
-
- /* Function to call before the statement walk occurring after the
- recursive walk of the dominator children. */
- void (*after_dom_children_before_stmts) (struct dom_walk_data *,
- basic_block);
-
- /* Function to call to walk statements after the recursive walk
- of the dominator children. */
- void (*after_dom_children_walk_stmts) (struct dom_walk_data *,
- basic_block, block_stmt_iterator);
-
- /* Function to call after the statement walk occurring after the
- recursive walk of the dominator children.
-
- This typically finalizes any block local data and pops
- that data from BLOCK_DATA_STACK. */
- void (*after_dom_children_after_stmts) (struct dom_walk_data *,
- basic_block);
-
- /* Global data for a walk through the dominator tree. */
- void *global_data;
-
- /* Stack of any data we need to keep on a per-block basis.
-
- If you have no local data, then BLOCK_DATA_STACK will be NULL. */
- VEC(void_p,heap) *block_data_stack;
-
- /* Size of the block local data. If this is zero, then it is assumed
- you have no local data and thus no BLOCK_DATA_STACK as well. */
- size_t block_local_data_size;
-
- /* From here below are private data. Please do not use this
- information/data outside domwalk.c. */
-
- /* Stack of available block local structures. */
- VEC(void_p,heap) *free_block_data;
-
- /* Interesting blocks to process. If this field is not NULL, this
- set is used to determine which blocks to walk. If we encounter
- block I in the dominator traversal, but block I is not present in
- INTERESTING_BLOCKS, then none of the callback functions are
- invoked on it. This is useful when a particular traversal wants
- to filter out non-interesting blocks from the dominator tree. */
- sbitmap interesting_blocks;
+ const ENUM_BITFIELD (cdi_direction) m_dom_direction : 2;
+ const ENUM_BITFIELD (reachability) m_reachability : 2;
+ bool m_user_bb_to_rpo;
+ basic_block m_unreachable_dom;
+ int *m_bb_to_rpo;
+
+ /* Query whether or not the given block is reachable or not. */
+ bool bb_reachable (struct function *, basic_block);
+
+ /* Given an unreachable block, propagate that property to outgoing
+ and possibly incoming edges for the block. Typically called after
+ determining a block is unreachable in the before_dom_children
+ callback. */
+ void propagate_unreachable_to_edges (basic_block, FILE *, dump_flags_t);
+
};
-void walk_dominator_tree (struct dom_walk_data *, basic_block);
-void init_walk_dominator_tree (struct dom_walk_data *);
-void fini_walk_dominator_tree (struct dom_walk_data *);
+extern void set_all_edges_as_executable (function *fn);
+
+#endif