SPIRV-Cross/spirv_cfg.hpp

/*
 * Copyright 2016-2021 Arm Limited
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 * 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.
 */

/*
 * At your option, you may choose to accept this material under either:
 *  1. The Apache License, Version 2.0, found at <http://www.apache.org/licenses/LICENSE-2.0>, or
 *  2. The MIT License, found at <http://opensource.org/licenses/MIT>.
 */

#ifndef SPIRV_CROSS_CFG_HPP
#define SPIRV_CROSS_CFG_HPP

#include "spirv_common.hpp"
#include <assert.h>

namespace SPIRV_CROSS_NAMESPACE
{
class Compiler;
class CFG
{
public:
    CFG(Compiler &compiler, const SPIRFunction &function);

    Compiler &get_compiler()
    {
        return compiler;
    }

    const Compiler &get_compiler() const
    {
        return compiler;
    }

    const SPIRFunction &get_function() const
    {
        return func;
    }

    uint32_t get_immediate_dominator(uint32_t block) const
    {
        auto itr = immediate_dominators.find(block);
        if (itr != std::end(immediate_dominators))
            return itr->second;
        else
            return 0;
    }

    bool is_reachable(uint32_t block) const
    {
        return visit_order.count(block) != 0;
    }

    uint32_t get_visit_order(uint32_t block) const
    {
        auto itr = visit_order.find(block);
        assert(itr != std::end(visit_order));
        int v = itr->second.get();
        assert(v > 0);
        return uint32_t(v);
    }

    uint32_t find_common_dominator(uint32_t a, uint32_t b) const;

    const SmallVector<uint32_t> &get_preceding_edges(uint32_t block) const
    {
        auto itr = preceding_edges.find(block);
        if (itr != std::end(preceding_edges))
            return itr->second;
        else
            return empty_vector;
    }

    const SmallVector<uint32_t> &get_succeeding_edges(uint32_t block) const
    {
        auto itr = succeeding_edges.find(block);
        if (itr != std::end(succeeding_edges))
            return itr->second;
        else
            return empty_vector;
    }

    template <typename Op>
    void walk_from(std::unordered_set<uint32_t> &seen_blocks, uint32_t block, const Op &op) const
    {
        if (seen_blocks.count(block))
            return;
        seen_blocks.insert(block);

        if (op(block))
        {
            for (auto b : get_succeeding_edges(block))
                walk_from(seen_blocks, b, op);
        }
    }

    uint32_t find_loop_dominator(uint32_t block) const;

    bool node_terminates_control_flow_in_sub_graph(BlockID from, BlockID to) const;

private:
    struct VisitOrder
    {
        int &get()
        {
            return v;
        }

        const int &get() const
        {
            return v;
        }

        int v = -1;
    };

    Compiler &compiler;
    const SPIRFunction &func;
    std::unordered_map<uint32_t, SmallVector<uint32_t>> preceding_edges;
    std::unordered_map<uint32_t, SmallVector<uint32_t>> succeeding_edges;
    std::unordered_map<uint32_t, uint32_t> immediate_dominators;
    std::unordered_map<uint32_t, VisitOrder> visit_order;
    SmallVector<uint32_t> post_order;
    SmallVector<uint32_t> empty_vector;

    void add_branch(uint32_t from, uint32_t to);
    void build_post_order_visit_order();
    void build_immediate_dominators();
    bool post_order_visit(uint32_t block);
    uint32_t visit_count = 0;

    bool is_back_edge(uint32_t to) const;
    bool has_visited_forward_edge(uint32_t to) const;
};

class DominatorBuilder
{
public:
    DominatorBuilder(const CFG &cfg);

    void add_block(uint32_t block);
    uint32_t get_dominator() const
    {
        return dominator;
    }

    void lift_continue_block_dominator();

private:
    const CFG &cfg;
    uint32_t dominator = 0;
};
} // namespace SPIRV_CROSS_NAMESPACE

#endif