306 lines
12 KiB
C++
306 lines
12 KiB
C++
// Copyright (c) 2017 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SOURCE_OPT_DOMINATOR_TREE_H_
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#define SOURCE_OPT_DOMINATOR_TREE_H_
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#include <algorithm>
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#include <cstdint>
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#include <map>
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#include <utility>
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#include <vector>
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#include "source/opt/cfg.h"
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#include "source/opt/tree_iterator.h"
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namespace spvtools {
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namespace opt {
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// This helper struct forms the nodes in the tree, with each node containing its
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// children. It also contains two values, for the pre and post indexes in the
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// tree which are used to compare two nodes.
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struct DominatorTreeNode {
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explicit DominatorTreeNode(BasicBlock* bb)
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: bb_(bb),
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parent_(nullptr),
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children_({}),
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dfs_num_pre_(-1),
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dfs_num_post_(-1) {}
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using iterator = std::vector<DominatorTreeNode*>::iterator;
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using const_iterator = std::vector<DominatorTreeNode*>::const_iterator;
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// depth first preorder iterator.
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using df_iterator = TreeDFIterator<DominatorTreeNode>;
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using const_df_iterator = TreeDFIterator<const DominatorTreeNode>;
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// depth first postorder iterator.
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using post_iterator = PostOrderTreeDFIterator<DominatorTreeNode>;
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using const_post_iterator = PostOrderTreeDFIterator<const DominatorTreeNode>;
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iterator begin() { return children_.begin(); }
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iterator end() { return children_.end(); }
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const_iterator begin() const { return cbegin(); }
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const_iterator end() const { return cend(); }
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const_iterator cbegin() const { return children_.begin(); }
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const_iterator cend() const { return children_.end(); }
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// Depth first preorder iterator using this node as root.
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df_iterator df_begin() { return df_iterator(this); }
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df_iterator df_end() { return df_iterator(); }
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const_df_iterator df_begin() const { return df_cbegin(); }
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const_df_iterator df_end() const { return df_cend(); }
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const_df_iterator df_cbegin() const { return const_df_iterator(this); }
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const_df_iterator df_cend() const { return const_df_iterator(); }
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// Depth first postorder iterator using this node as root.
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post_iterator post_begin() { return post_iterator::begin(this); }
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post_iterator post_end() { return post_iterator::end(nullptr); }
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const_post_iterator post_begin() const { return post_cbegin(); }
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const_post_iterator post_end() const { return post_cend(); }
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const_post_iterator post_cbegin() const {
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return const_post_iterator::begin(this);
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}
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const_post_iterator post_cend() const {
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return const_post_iterator::end(nullptr);
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}
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inline uint32_t id() const { return bb_->id(); }
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BasicBlock* bb_;
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DominatorTreeNode* parent_;
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std::vector<DominatorTreeNode*> children_;
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// These indexes are used to compare two given nodes. A node is a child or
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// grandchild of another node if its preorder index is greater than the
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// first nodes preorder index AND if its postorder index is less than the
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// first nodes postorder index.
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int dfs_num_pre_;
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int dfs_num_post_;
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};
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// A class representing a tree of BasicBlocks in a given function, where each
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// node is dominated by its parent.
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class DominatorTree {
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public:
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// Map OpLabel ids to dominator tree nodes
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using DominatorTreeNodeMap = std::map<uint32_t, DominatorTreeNode>;
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using iterator = TreeDFIterator<DominatorTreeNode>;
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using const_iterator = TreeDFIterator<const DominatorTreeNode>;
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using post_iterator = PostOrderTreeDFIterator<DominatorTreeNode>;
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using const_post_iterator = PostOrderTreeDFIterator<const DominatorTreeNode>;
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// List of DominatorTreeNode to define the list of roots
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using DominatorTreeNodeList = std::vector<DominatorTreeNode*>;
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using roots_iterator = DominatorTreeNodeList::iterator;
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using roots_const_iterator = DominatorTreeNodeList::const_iterator;
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DominatorTree() : postdominator_(false) {}
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explicit DominatorTree(bool post) : postdominator_(post) {}
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// Depth first iterators.
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// Traverse the dominator tree in a depth first pre-order.
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// The pseudo-block is ignored.
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iterator begin() { return ++iterator(GetRoot()); }
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iterator end() { return iterator(); }
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const_iterator begin() const { return cbegin(); }
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const_iterator end() const { return cend(); }
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const_iterator cbegin() const { return ++const_iterator(GetRoot()); }
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const_iterator cend() const { return const_iterator(); }
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// Traverse the dominator tree in a depth first post-order.
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// The pseudo-block is ignored.
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post_iterator post_begin() { return post_iterator::begin(GetRoot()); }
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post_iterator post_end() { return post_iterator::end(GetRoot()); }
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const_post_iterator post_begin() const { return post_cbegin(); }
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const_post_iterator post_end() const { return post_cend(); }
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const_post_iterator post_cbegin() const {
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return const_post_iterator::begin(GetRoot());
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}
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const_post_iterator post_cend() const {
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return const_post_iterator::end(GetRoot());
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}
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roots_iterator roots_begin() { return roots_.begin(); }
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roots_iterator roots_end() { return roots_.end(); }
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roots_const_iterator roots_begin() const { return roots_cbegin(); }
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roots_const_iterator roots_end() const { return roots_cend(); }
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roots_const_iterator roots_cbegin() const { return roots_.begin(); }
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roots_const_iterator roots_cend() const { return roots_.end(); }
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// Get the unique root of the tree.
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// It is guaranteed to work on a dominator tree.
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// post-dominator might have a list.
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DominatorTreeNode* GetRoot() {
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assert(roots_.size() == 1);
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return *roots_.begin();
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}
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const DominatorTreeNode* GetRoot() const {
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assert(roots_.size() == 1);
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return *roots_.begin();
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}
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const DominatorTreeNodeList& Roots() const { return roots_; }
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// Dumps the tree in the graphvis dot format into the |out_stream|.
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void DumpTreeAsDot(std::ostream& out_stream) const;
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// Build the (post-)dominator tree for the given control flow graph
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// |cfg| and the function |f|. |f| must exist in the |cfg|. Any
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// existing data in the dominator tree will be overwritten
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void InitializeTree(const CFG& cfg, const Function* f);
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// Check if the basic block |a| dominates the basic block |b|.
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bool Dominates(const BasicBlock* a, const BasicBlock* b) const;
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// Check if the basic block id |a| dominates the basic block id |b|.
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bool Dominates(uint32_t a, uint32_t b) const;
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// Check if the dominator tree node |a| dominates the dominator tree node |b|.
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bool Dominates(const DominatorTreeNode* a, const DominatorTreeNode* b) const;
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// Check if the basic block |a| strictly dominates the basic block |b|.
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bool StrictlyDominates(const BasicBlock* a, const BasicBlock* b) const;
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// Check if the basic block id |a| strictly dominates the basic block id |b|.
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bool StrictlyDominates(uint32_t a, uint32_t b) const;
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// Check if the dominator tree node |a| strictly dominates the dominator tree
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// node |b|.
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bool StrictlyDominates(const DominatorTreeNode* a,
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const DominatorTreeNode* b) const;
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// Returns the immediate dominator of basic block |a|.
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BasicBlock* ImmediateDominator(const BasicBlock* A) const;
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// Returns the immediate dominator of basic block id |a|.
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BasicBlock* ImmediateDominator(uint32_t a) const;
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// Returns true if the basic block |a| is reachable by this tree. A node would
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// be unreachable if it cannot be reached by traversal from the start node or
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// for a postdominator tree, cannot be reached from the exit nodes.
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inline bool ReachableFromRoots(const BasicBlock* a) const {
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if (!a) return false;
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return ReachableFromRoots(a->id());
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}
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// Returns true if the basic block id |a| is reachable by this tree.
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bool ReachableFromRoots(uint32_t a) const {
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return GetTreeNode(a) != nullptr;
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}
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// Returns true if this tree is a post dominator tree.
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bool IsPostDominator() const { return postdominator_; }
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// Clean up the tree.
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void ClearTree() {
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nodes_.clear();
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roots_.clear();
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}
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// Applies the std::function |func| to all nodes in the dominator tree.
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// Tree nodes are visited in a depth first pre-order.
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bool Visit(std::function<bool(DominatorTreeNode*)> func) {
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for (auto n : *this) {
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if (!func(&n)) return false;
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}
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return true;
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}
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// Applies the std::function |func| to all nodes in the dominator tree.
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// Tree nodes are visited in a depth first pre-order.
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bool Visit(std::function<bool(const DominatorTreeNode*)> func) const {
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for (auto n : *this) {
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if (!func(&n)) return false;
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}
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return true;
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}
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// Applies the std::function |func| to all nodes in the dominator tree from
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// |node| downwards. The boolean return from |func| is used to determine
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// whether or not the children should also be traversed. Tree nodes are
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// visited in a depth first pre-order.
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void VisitChildrenIf(std::function<bool(DominatorTreeNode*)> func,
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iterator node) {
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if (func(&*node)) {
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for (auto n : *node) {
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VisitChildrenIf(func, n->df_begin());
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}
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}
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}
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// Returns the DominatorTreeNode associated with the basic block |bb|.
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// If the |bb| is unknown to the dominator tree, it returns null.
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inline DominatorTreeNode* GetTreeNode(BasicBlock* bb) {
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return GetTreeNode(bb->id());
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}
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// Returns the DominatorTreeNode associated with the basic block |bb|.
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// If the |bb| is unknown to the dominator tree, it returns null.
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inline const DominatorTreeNode* GetTreeNode(BasicBlock* bb) const {
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return GetTreeNode(bb->id());
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}
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// Returns the DominatorTreeNode associated with the basic block id |id|.
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// If the id |id| is unknown to the dominator tree, it returns null.
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inline DominatorTreeNode* GetTreeNode(uint32_t id) {
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DominatorTreeNodeMap::iterator node_iter = nodes_.find(id);
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if (node_iter == nodes_.end()) {
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return nullptr;
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}
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return &node_iter->second;
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}
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// Returns the DominatorTreeNode associated with the basic block id |id|.
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// If the id |id| is unknown to the dominator tree, it returns null.
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inline const DominatorTreeNode* GetTreeNode(uint32_t id) const {
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DominatorTreeNodeMap::const_iterator node_iter = nodes_.find(id);
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if (node_iter == nodes_.end()) {
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return nullptr;
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}
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return &node_iter->second;
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}
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// Adds the basic block |bb| to the tree structure if it doesn't already
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// exist.
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DominatorTreeNode* GetOrInsertNode(BasicBlock* bb);
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// Recomputes the DF numbering of the tree.
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void ResetDFNumbering();
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private:
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// Wrapper function which gets the list of pairs of each BasicBlocks to its
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// immediately dominating BasicBlock and stores the result in the edges
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// parameter.
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//
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// The |edges| vector will contain the dominator tree as pairs of nodes.
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// The first node in the pair is a node in the graph. The second node in the
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// pair is its immediate dominator.
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// The root of the tree has themself as immediate dominator.
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void GetDominatorEdges(
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const Function* f, const BasicBlock* dummy_start_node,
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std::vector<std::pair<BasicBlock*, BasicBlock*>>* edges);
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// The roots of the tree.
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std::vector<DominatorTreeNode*> roots_;
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// Pairs each basic block id to the tree node containing that basic block.
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DominatorTreeNodeMap nodes_;
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// True if this is a post dominator tree.
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bool postdominator_;
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};
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} // namespace opt
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} // namespace spvtools
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#endif // SOURCE_OPT_DOMINATOR_TREE_H_
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