mirror of
https://github.com/KhronosGroup/SPIRV-Tools
synced 2024-10-18 19:20:05 +00:00
228 lines
8.2 KiB
C++
228 lines
8.2 KiB
C++
// Copyright (c) 2015-2016 The Khronos Group Inc.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
#ifndef SPVTOOLS_CFA_H_
|
|
#define SPVTOOLS_CFA_H_
|
|
|
|
#include <algorithm>
|
|
#include <cassert>
|
|
#include <functional>
|
|
#include <map>
|
|
#include <unordered_map>
|
|
#include <unordered_set>
|
|
#include <utility>
|
|
#include <vector>
|
|
|
|
using std::find;
|
|
using std::function;
|
|
using std::get;
|
|
using std::pair;
|
|
using std::unordered_map;
|
|
using std::unordered_set;
|
|
using std::vector;
|
|
|
|
namespace spvtools {
|
|
|
|
// Control Flow Analysis of control flow graphs of basic block nodes |BB|.
|
|
template<class BB> class CFA {
|
|
using bb_ptr = BB*;
|
|
using cbb_ptr = const BB*;
|
|
using bb_iter = typename std::vector<BB*>::const_iterator;
|
|
using get_blocks_func =
|
|
std::function<const std::vector<BB*>*(const BB*)>;
|
|
|
|
struct block_info {
|
|
cbb_ptr block; ///< pointer to the block
|
|
bb_iter iter; ///< Iterator to the current child node being processed
|
|
};
|
|
|
|
/// Returns true if a block with @p id is found in the @p work_list vector
|
|
///
|
|
/// @param[in] work_list Set of blocks visited in the the depth first traversal
|
|
/// of the CFG
|
|
/// @param[in] id The ID of the block being checked
|
|
///
|
|
/// @return true if the edge work_list.back().block->id() => id is a back-edge
|
|
static bool FindInWorkList(
|
|
const std::vector<block_info>& work_list, uint32_t id);
|
|
|
|
public:
|
|
/// @brief Depth first traversal starting from the \p entry BasicBlock
|
|
///
|
|
/// This function performs a depth first traversal from the \p entry
|
|
/// BasicBlock and calls the pre/postorder functions when it needs to process
|
|
/// the node in pre order, post order. It also calls the backedge function
|
|
/// when a back edge is encountered.
|
|
///
|
|
/// @param[in] entry The root BasicBlock of a CFG
|
|
/// @param[in] successor_func A function which will return a pointer to the
|
|
/// successor nodes
|
|
/// @param[in] preorder A function that will be called for every block in a
|
|
/// CFG following preorder traversal semantics
|
|
/// @param[in] postorder A function that will be called for every block in a
|
|
/// CFG following postorder traversal semantics
|
|
/// @param[in] backedge A function that will be called when a backedge is
|
|
/// encountered during a traversal
|
|
/// NOTE: The @p successor_func and predecessor_func each return a pointer to a
|
|
/// collection such that iterators to that collection remain valid for the
|
|
/// lifetime of the algorithm.
|
|
static void DepthFirstTraversal(const BB* entry,
|
|
get_blocks_func successor_func,
|
|
std::function<void(cbb_ptr)> preorder,
|
|
std::function<void(cbb_ptr)> postorder,
|
|
std::function<void(cbb_ptr, cbb_ptr)> backedge);
|
|
|
|
/// @brief Calculates dominator edges for a set of blocks
|
|
///
|
|
/// Computes dominators using the algorithm of Cooper, Harvey, and Kennedy
|
|
/// "A Simple, Fast Dominance Algorithm", 2001.
|
|
///
|
|
/// The algorithm assumes there is a unique root node (a node without
|
|
/// predecessors), and it is therefore at the end of the postorder vector.
|
|
///
|
|
/// This function calculates the dominator edges for a set of blocks in the CFG.
|
|
/// Uses the dominator algorithm by Cooper et al.
|
|
///
|
|
/// @param[in] postorder A vector of blocks in post order traversal order
|
|
/// in a CFG
|
|
/// @param[in] predecessor_func Function used to get the predecessor nodes of a
|
|
/// block
|
|
///
|
|
/// @return the dominator tree of the graph, as a vector of pairs of nodes.
|
|
/// The first node in the pair is a node in the graph. The second node in the
|
|
/// pair is its immediate dominator in the sense of Cooper et.al., where a block
|
|
/// without predecessors (such as the root node) is its own immediate dominator.
|
|
static vector<pair<BB*, BB*>> CalculateDominators(
|
|
const vector<cbb_ptr>& postorder, get_blocks_func predecessor_func);
|
|
};
|
|
|
|
template<class BB> bool CFA<BB>::FindInWorkList(const vector<block_info>& work_list,
|
|
uint32_t id) {
|
|
for (const auto b : work_list) {
|
|
if (b.block->id() == id) return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
template<class BB> void CFA<BB>::DepthFirstTraversal(const BB* entry,
|
|
get_blocks_func successor_func,
|
|
function<void(cbb_ptr)> preorder,
|
|
function<void(cbb_ptr)> postorder,
|
|
function<void(cbb_ptr, cbb_ptr)> backedge) {
|
|
unordered_set<uint32_t> processed;
|
|
|
|
/// NOTE: work_list is the sequence of nodes from the root node to the node
|
|
/// being processed in the traversal
|
|
vector<block_info> work_list;
|
|
work_list.reserve(10);
|
|
|
|
work_list.push_back({ entry, begin(*successor_func(entry)) });
|
|
preorder(entry);
|
|
processed.insert(entry->id());
|
|
|
|
while (!work_list.empty()) {
|
|
block_info& top = work_list.back();
|
|
if (top.iter == end(*successor_func(top.block))) {
|
|
postorder(top.block);
|
|
work_list.pop_back();
|
|
}
|
|
else {
|
|
BB* child = *top.iter;
|
|
top.iter++;
|
|
if (FindInWorkList(work_list, child->id())) {
|
|
backedge(top.block, child);
|
|
}
|
|
if (processed.count(child->id()) == 0) {
|
|
preorder(child);
|
|
work_list.emplace_back(
|
|
block_info{ child, begin(*successor_func(child)) });
|
|
processed.insert(child->id());
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
template<class BB>
|
|
vector<pair<BB*, BB*>> CFA<BB>::CalculateDominators(
|
|
const vector<cbb_ptr>& postorder, get_blocks_func predecessor_func) {
|
|
struct block_detail {
|
|
size_t dominator; ///< The index of blocks's dominator in post order array
|
|
size_t postorder_index; ///< The index of the block in the post order array
|
|
};
|
|
const size_t undefined_dom = postorder.size();
|
|
|
|
unordered_map<cbb_ptr, block_detail> idoms;
|
|
for (size_t i = 0; i < postorder.size(); i++) {
|
|
idoms[postorder[i]] = { undefined_dom, i };
|
|
}
|
|
idoms[postorder.back()].dominator = idoms[postorder.back()].postorder_index;
|
|
|
|
bool changed = true;
|
|
while (changed) {
|
|
changed = false;
|
|
for (auto b = postorder.rbegin() + 1; b != postorder.rend(); ++b) {
|
|
const vector<BB*>& predecessors = *predecessor_func(*b);
|
|
// Find the first processed/reachable predecessor that is reachable
|
|
// in the forward traversal.
|
|
auto res = find_if(begin(predecessors), end(predecessors),
|
|
[&idoms, undefined_dom](BB* pred) {
|
|
return idoms.count(pred) &&
|
|
idoms[pred].dominator != undefined_dom;
|
|
});
|
|
if (res == end(predecessors)) continue;
|
|
const BB* idom = *res;
|
|
size_t idom_idx = idoms[idom].postorder_index;
|
|
|
|
// all other predecessors
|
|
for (const auto* p : predecessors) {
|
|
if (idom == p) continue;
|
|
// Only consider nodes reachable in the forward traversal.
|
|
// Otherwise the intersection doesn't make sense and will never
|
|
// terminate.
|
|
if (!idoms.count(p)) continue;
|
|
if (idoms[p].dominator != undefined_dom) {
|
|
size_t finger1 = idoms[p].postorder_index;
|
|
size_t finger2 = idom_idx;
|
|
while (finger1 != finger2) {
|
|
while (finger1 < finger2) {
|
|
finger1 = idoms[postorder[finger1]].dominator;
|
|
}
|
|
while (finger2 < finger1) {
|
|
finger2 = idoms[postorder[finger2]].dominator;
|
|
}
|
|
}
|
|
idom_idx = finger1;
|
|
}
|
|
}
|
|
if (idoms[*b].dominator != idom_idx) {
|
|
idoms[*b].dominator = idom_idx;
|
|
changed = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
vector<pair<bb_ptr, bb_ptr>> out;
|
|
for (auto idom : idoms) {
|
|
// NOTE: performing a const cast for convenient usage with
|
|
// UpdateImmediateDominators
|
|
out.push_back({ const_cast<BB*>(get<0>(idom)),
|
|
const_cast<BB*>(postorder[get<1>(idom).dominator]) });
|
|
}
|
|
return out;
|
|
}
|
|
|
|
} // namespace spvtools
|
|
|
|
#endif // SPVTOOLS_CFA_H_
|