1 // Copyright (c) 2017 Google Inc.
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
7 // http://www.apache.org/licenses/LICENSE-2.0
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
17 #include "ir_context.h"
25 // Universal Limit of ResultID + 1
26 const int kInvalidId = 0x400000;
30 CFG::CFG(ir::Module* module)
32 pseudo_entry_block_(std::unique_ptr<ir::Instruction>(
33 new ir::Instruction(module->context(), SpvOpLabel, 0, 0, {}))),
34 pseudo_exit_block_(std::unique_ptr<ir::Instruction>(new ir::Instruction(
35 module->context(), SpvOpLabel, 0, kInvalidId, {}))) {
36 for (auto& fn : *module) {
37 for (auto& blk : fn) {
43 void CFG::AddEdges(ir::BasicBlock* blk) {
44 uint32_t blk_id = blk->id();
45 // Force the creation of an entry, not all basic block have predecessors
46 // (such as the entry blocks and some unreachables).
48 const auto* const_blk = blk;
49 const_blk->ForEachSuccessorLabel(
50 [blk_id, this](const uint32_t succ_id) { AddEdge(blk_id, succ_id); });
53 void CFG::RemoveNonExistingEdges(uint32_t blk_id) {
54 std::vector<uint32_t> updated_pred_list;
55 for (uint32_t id : preds(blk_id)) {
56 const ir::BasicBlock* pred_blk = block(id);
57 bool has_branch = false;
58 pred_blk->ForEachSuccessorLabel([&has_branch, blk_id](uint32_t succ) {
59 if (succ == blk_id) has_branch = true;
61 if (has_branch) updated_pred_list.push_back(id);
64 label2preds_.at(blk_id) = std::move(updated_pred_list);
67 void CFG::ComputeStructuredOrder(ir::Function* func, ir::BasicBlock* root,
68 std::list<ir::BasicBlock*>* order) {
69 assert(module_->context()->get_feature_mgr()->HasCapability(
70 SpvCapabilityShader) &&
71 "This only works on structured control flow");
73 // Compute structured successors and do DFS.
74 ComputeStructuredSuccessors(func);
75 auto ignore_block = [](cbb_ptr) {};
76 auto ignore_edge = [](cbb_ptr, cbb_ptr) {};
77 auto get_structured_successors = [this](const ir::BasicBlock* b) {
78 return &(block2structured_succs_[b]);
81 // TODO(greg-lunarg): Get rid of const_cast by making moving const
82 // out of the cfa.h prototypes and into the invoking code.
83 auto post_order = [&](cbb_ptr b) {
84 order->push_front(const_cast<ir::BasicBlock*>(b));
86 spvtools::CFA<ir::BasicBlock>::DepthFirstTraversal(
87 root, get_structured_successors, ignore_block, post_order, ignore_edge);
90 void CFG::ForEachBlockInReversePostOrder(
91 BasicBlock* bb, const std::function<void(BasicBlock*)>& f) {
92 std::vector<BasicBlock*> po;
93 std::unordered_set<BasicBlock*> seen;
94 ComputePostOrderTraversal(bb, &po, &seen);
96 for (auto current_bb = po.rbegin(); current_bb != po.rend(); ++current_bb) {
97 if (!IsPseudoExitBlock(*current_bb) && !IsPseudoEntryBlock(*current_bb)) {
103 void CFG::ComputeStructuredSuccessors(ir::Function* func) {
104 block2structured_succs_.clear();
105 for (auto& blk : *func) {
106 // If no predecessors in function, make successor to pseudo entry.
107 if (label2preds_[blk.id()].size() == 0)
108 block2structured_succs_[&pseudo_entry_block_].push_back(&blk);
110 // If header, make merge block first successor and continue block second
111 // successor if there is one.
112 uint32_t mbid = blk.MergeBlockIdIfAny();
114 block2structured_succs_[&blk].push_back(id2block_[mbid]);
115 uint32_t cbid = blk.ContinueBlockIdIfAny();
116 if (cbid != 0) block2structured_succs_[&blk].push_back(id2block_[cbid]);
119 // Add true successors.
120 const auto& const_blk = blk;
121 const_blk.ForEachSuccessorLabel([&blk, this](const uint32_t sbid) {
122 block2structured_succs_[&blk].push_back(id2block_[sbid]);
127 void CFG::ComputePostOrderTraversal(BasicBlock* bb, vector<BasicBlock*>* order,
128 unordered_set<BasicBlock*>* seen) {
130 static_cast<const BasicBlock*>(bb)->ForEachSuccessorLabel(
131 [&order, &seen, this](const uint32_t sbid) {
132 BasicBlock* succ_bb = id2block_[sbid];
133 if (!seen->count(succ_bb)) {
134 ComputePostOrderTraversal(succ_bb, order, seen);
137 order->push_back(bb);
141 } // namespace spvtools