src/tint/lang/msl/writer/common/option_helpers.cc

/// Copyright 2023 The Dawn & Tint Authors
//
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// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
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#include "src/tint/lang/msl/writer/common/option_helpers.h"

#include <utility>

#include "src/tint/utils/containers/hashset.h"

namespace tint::msl::writer {

/// binding::BindingInfo to tint::BindingPoint map
using InfoToPointMap = tint::Hashmap<binding::BindingInfo, tint::BindingPoint, 8>;

Result<SuccessType> ValidateBindingOptions(const Options& options) {
    diag::List diagnostics;

    tint::Hashmap<tint::BindingPoint, binding::BindingInfo, 8> seen_wgsl_bindings{};

    InfoToPointMap seen_msl_buffer_bindings{};
    InfoToPointMap seen_msl_texture_bindings{};
    InfoToPointMap seen_msl_sampler_bindings{};

    // Both wgsl_seen and spirv_seen check to see if the pair of [src, dst] are unique. If we have
    // multiple entries that map the same [src, dst] pair, that's fine. We treat it as valid as it's
    // possible for multiple entry points to use the remapper at the same time. If the pair doesn't
    // match, then we report an error about a duplicate binding point.

    auto wgsl_seen = [&diagnostics, &seen_wgsl_bindings](const tint::BindingPoint& src,
                                                         const binding::BindingInfo& dst) -> bool {
        if (auto binding = seen_wgsl_bindings.Find(src)) {
            if (*binding != dst) {
                std::stringstream str;
                str << "found duplicate WGSL binding point: " << src;

                diagnostics.add_error(diag::System::Writer, str.str());
                return true;
            }
        }
        seen_wgsl_bindings.Add(src, dst);
        return false;
    };

    auto msl_seen = [&diagnostics](InfoToPointMap& map, const binding::BindingInfo& src,
                                   const tint::BindingPoint& dst) -> bool {
        if (auto binding = map.Find(src)) {
            if (*binding != dst) {
                std::stringstream str;
                str << "found duplicate MSL binding point: [binding: " << src.binding << "]";
                diagnostics.add_error(diag::System::Writer, str.str());
                return true;
            }
        }
        map.Add(src, dst);
        return false;
    };

    auto valid = [&wgsl_seen, &msl_seen](InfoToPointMap& map, const auto& hsh) -> bool {
        for (const auto& it : hsh) {
            const auto& src_binding = it.first;
            const auto& dst_binding = it.second;

            if (wgsl_seen(src_binding, dst_binding)) {
                return false;
            }

            if (msl_seen(map, dst_binding, src_binding)) {
                return false;
            }
        }
        return true;
    };

    // Storage and uniform are both [[buffer()]]
    if (!valid(seen_msl_buffer_bindings, options.bindings.uniform)) {
        diagnostics.add_note(diag::System::Writer, "when processing uniform", {});
        return Failure{std::move(diagnostics)};
    }
    if (!valid(seen_msl_buffer_bindings, options.bindings.storage)) {
        diagnostics.add_note(diag::System::Writer, "when processing storage", {});
        return Failure{std::move(diagnostics)};
    }

    // Sampler is [[sampler()]]
    if (!valid(seen_msl_sampler_bindings, options.bindings.sampler)) {
        diagnostics.add_note(diag::System::Writer, "when processing sampler", {});
        return Failure{std::move(diagnostics)};
    }

    // Texture and storage texture are [[texture()]]
    if (!valid(seen_msl_texture_bindings, options.bindings.texture)) {
        diagnostics.add_note(diag::System::Writer, "when processing texture", {});
        return Failure{std::move(diagnostics)};
    }
    if (!valid(seen_msl_texture_bindings, options.bindings.storage_texture)) {
        diagnostics.add_note(diag::System::Writer, "when processing storage_texture", {});
        return Failure{std::move(diagnostics)};
    }

    for (const auto& it : options.bindings.external_texture) {
        const auto& src_binding = it.first;
        const auto& plane0 = it.second.plane0;
        const auto& plane1 = it.second.plane1;
        const auto& metadata = it.second.metadata;

        // Validate with the actual source regardless of what the remapper will do
        if (wgsl_seen(src_binding, plane0)) {
            diagnostics.add_note(diag::System::Writer, "when processing external_texture", {});
            return Failure{std::move(diagnostics)};
        }

        // Plane0 & Plane1 are [[texture()]]
        if (msl_seen(seen_msl_texture_bindings, plane0, src_binding)) {
            diagnostics.add_note(diag::System::Writer, "when processing external_texture", {});
            return Failure{std::move(diagnostics)};
        }
        if (msl_seen(seen_msl_texture_bindings, plane1, src_binding)) {
            diagnostics.add_note(diag::System::Writer, "when processing external_texture", {});
            return Failure{std::move(diagnostics)};
        }
        // Metadata is [[buffer()]]
        if (msl_seen(seen_msl_buffer_bindings, metadata, src_binding)) {
            diagnostics.add_note(diag::System::Writer, "when processing external_texture", {});
            return Failure{std::move(diagnostics)};
        }
    }

    return Success;
}

// The remapped binding data and external texture data need to coordinate in order to put things in
// the correct place when we're done. The binding remapper is run first, so make sure that the
// external texture uses the new binding point.
//
// When the data comes in we have a list of all WGSL origin (group,binding) pairs to MSL
// (binding) in the `uniform`, `storage`, `texture`, and `sampler` arrays.
void PopulateRemapperAndMultiplanarOptions(const Options& options,
                                           RemapperData& remapper_data,
                                           ExternalTextureOptions& external_texture) {
    auto create_remappings = [&remapper_data](const auto& hsh) {
        for (const auto& it : hsh) {
            const BindingPoint& src_binding_point = it.first;
            const binding::Uniform& dst_binding_point = it.second;

            // Bindings which go to the same slot in MSL do not need to be re-bound.
            if (src_binding_point.group == 0 &&
                src_binding_point.binding == dst_binding_point.binding) {
                continue;
            }

            remapper_data.emplace(src_binding_point, BindingPoint{0, dst_binding_point.binding});
        }
    };

    create_remappings(options.bindings.uniform);
    create_remappings(options.bindings.storage);
    create_remappings(options.bindings.texture);
    create_remappings(options.bindings.storage_texture);
    create_remappings(options.bindings.sampler);

    // External textures are re-bound to their plane0 location
    for (const auto& it : options.bindings.external_texture) {
        const BindingPoint& src_binding_point = it.first;

        const binding::BindingInfo& plane0 = it.second.plane0;
        const binding::BindingInfo& plane1 = it.second.plane1;
        const binding::BindingInfo& metadata = it.second.metadata;

        BindingPoint plane0_binding_point{0, plane0.binding};
        BindingPoint plane1_binding_point{0, plane1.binding};
        BindingPoint metadata_binding_point{0, metadata.binding};

        // Use the re-bound MSL plane0 value for the lookup key. The group goes to `0` which is the
        // value always used for re-bound data.
        external_texture.bindings_map.emplace(
            BindingPoint{0, plane0_binding_point.binding},
            ExternalTextureOptions::BindingPoints{plane1_binding_point, metadata_binding_point});

        // Bindings which go to the same slot in MSL do not need to be re-bound.
        if (src_binding_point == plane0_binding_point) {
            continue;
        }

        remapper_data.emplace(src_binding_point, plane0_binding_point);
    }
}

}  // namespace tint::msl::writer

namespace std {

/// Custom std::hash specialization for tint::msl::writer::binding::BindingInfo so
/// they can be used as keys for std::unordered_map and std::unordered_set.
template <>
class hash<tint::msl::writer::binding::BindingInfo> {
  public:
    /// @param info the binding to create a hash for
    /// @return the hash value
    inline std::size_t operator()(const tint::msl::writer::binding::BindingInfo& info) const {
        return tint::Hash(info.binding);
    }
};

}  // namespace std