116 lines
4.5 KiB
C
116 lines
4.5 KiB
C
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/* Generic dominator tree walker
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Copyright (C) 2003-2023 Free Software Foundation, Inc.
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Contributed by Diego Novillo <dnovillo@redhat.com>
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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GCC is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#ifndef GCC_DOM_WALK_H
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#define GCC_DOM_WALK_H
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/**
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* This is the main class for the dominator walker. It is expected that
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* consumers will have a custom class inheriting from it, which will over ride
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* at least one of before_dom_children and after_dom_children to implement the
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* custom behavior.
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*/
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class dom_walker
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{
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public:
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static const edge STOP;
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/* An enum for determining whether the dom walk should be constrained to
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blocks reachable by executable edges. */
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enum reachability
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{
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/* Walk all blocks within the CFG. */
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ALL_BLOCKS,
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/* Use REACHABLE_BLOCKS when your subclass can discover that some edges
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are not executable.
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If a subclass can discover that a COND, SWITCH or GOTO has a static
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target in the before_dom_children callback, the taken edge should
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be returned. The generic walker will clear EDGE_EXECUTABLE on all
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edges it can determine are not executable.
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With REACHABLE_BLOCKS, EDGE_EXECUTABLE will be set on every edge in
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the dom_walker ctor; the flag will then be cleared on edges that are
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determined to be not executable. */
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REACHABLE_BLOCKS,
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/* Identical to REACHABLE_BLOCKS, but the initial state of EDGE_EXECUTABLE
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will instead be preserved in the ctor, allowing for information about
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non-executable edges to be merged in from an earlier analysis (and
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potentially for additional edges to be marked as non-executable). */
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REACHABLE_BLOCKS_PRESERVING_FLAGS
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};
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/* You can provide a mapping of basic-block index to RPO if you
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have that readily available or you do multiple walks. If you
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specify NULL as BB_INDEX_TO_RPO this mapping will be computed
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lazily at walk time. If you specify -1 dominator children will
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not be walked in RPO order. */
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dom_walker (cdi_direction direction, enum reachability = ALL_BLOCKS,
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int *bb_index_to_rpo = NULL);
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~dom_walker ();
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/* Walk the dominator tree. */
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void walk (basic_block);
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/* Function to call before the recursive walk of the dominator children.
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Return value is the always taken edge if the block has multiple outgoing
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edges, NULL otherwise. When skipping unreachable blocks, the walker
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uses the taken edge information to clear EDGE_EXECUTABLE on the other
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edges, exposing unreachable blocks. A NULL return value means all
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outgoing edges should still be considered executable. A return value
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of STOP means to stop the domwalk from processing dominated blocks from
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here. This can be used to process a SEME region only (note domwalk
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will still do work linear in function size). */
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virtual edge before_dom_children (basic_block) { return NULL; }
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/* Function to call after the recursive walk of the dominator children. */
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virtual void after_dom_children (basic_block) {}
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private:
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/* This is the direction of the dominator tree we want to walk. i.e.,
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if it is set to CDI_DOMINATORS, then we walk the dominator tree,
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if it is set to CDI_POST_DOMINATORS, then we walk the post
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dominator tree. */
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const ENUM_BITFIELD (cdi_direction) m_dom_direction : 2;
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const ENUM_BITFIELD (reachability) m_reachability : 2;
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bool m_user_bb_to_rpo;
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basic_block m_unreachable_dom;
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int *m_bb_to_rpo;
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/* Query whether or not the given block is reachable or not. */
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bool bb_reachable (struct function *, basic_block);
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/* Given an unreachable block, propagate that property to outgoing
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and possibly incoming edges for the block. Typically called after
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determining a block is unreachable in the before_dom_children
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callback. */
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void propagate_unreachable_to_edges (basic_block, FILE *, dump_flags_t);
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};
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extern void set_all_edges_as_executable (function *fn);
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#endif
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