src/tint/lang/spirv/writer/helpers/generate_bindings.cc

// Copyright 2023 The Dawn & Tint Authors
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#include "src/tint/lang/spirv/writer/helpers/generate_bindings.h"

#include <algorithm>

#include "src/tint/api/common/binding_point.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/var.h"
#include "src/tint/lang/core/type/external_texture.h"
#include "src/tint/lang/core/type/pointer.h"
#include "src/tint/lang/core/type/storage_texture.h"
#include "src/tint/utils/containers/hashmap.h"
#include "src/tint/utils/containers/vector.h"
#include "src/tint/utils/rtti/switch.h"

namespace tint::spirv::writer {

Bindings GenerateBindings(const core::ir::Module& module) {
    Bindings bindings{};
    if (!module.root_block) {
        return bindings;
    }

    // Collect next valid binding number per group
    Hashmap<uint32_t, uint32_t, 4> group_to_next_binding_number;
    Vector<tint::BindingPoint, 4> ext_tex_bps;
    for (auto* inst : *module.root_block) {
        if (!inst->Alive()) {
            continue;
        }
        auto* var = inst->As<core::ir::Var>();
        if (auto bp = var->BindingPoint()) {
            if (auto val = group_to_next_binding_number.Get(bp->group)) {
                *val = std::max(*val, bp->binding + 1);
            } else {
                group_to_next_binding_number.Add(bp->group, bp->binding + 1);
            }

            auto* ptr = var->Result(0)->Type()->As<core::type::Pointer>();
            auto* ty = ptr->UnwrapPtr();

            // Store up the external textures, we'll add them in the next step
            if (ty->Is<core::type::ExternalTexture>()) {
                ext_tex_bps.Push(*bp);
                continue;
            }

            binding::BindingInfo info{bp->group, bp->binding};
            switch (ptr->AddressSpace()) {
                case core::AddressSpace::kHandle:
                    Switch(
                        ptr->UnwrapPtr(),  //
                        [&](const core::type::Sampler*) { bindings.sampler.emplace(*bp, info); },
                        [&](const core::type::StorageTexture*) {
                            bindings.storage_texture.emplace(*bp, info);
                        },
                        [&](const core::type::Texture*) { bindings.texture.emplace(*bp, info); });
                    break;
                case core::AddressSpace::kStorage:
                    bindings.storage.emplace(*bp, info);
                    break;
                case core::AddressSpace::kUniform:
                    bindings.uniform.emplace(*bp, info);
                    break;

                case core::AddressSpace::kUndefined:
                case core::AddressSpace::kPixelLocal:
                case core::AddressSpace::kPrivate:
                case core::AddressSpace::kPushConstant:
                case core::AddressSpace::kIn:
                case core::AddressSpace::kOut:
                case core::AddressSpace::kFunction:
                case core::AddressSpace::kWorkgroup:
                    break;
            }
        }
    }

    for (auto bp : ext_tex_bps) {
        uint32_t g = bp.group;
        uint32_t& next_num = group_to_next_binding_number.GetOrAddZero(g);

        binding::BindingInfo plane0{bp.group, bp.binding};
        binding::BindingInfo plane1{g, next_num++};
        binding::BindingInfo metadata{g, next_num++};

        bindings.external_texture.emplace(bp, binding::ExternalTexture{metadata, plane0, plane1});
    }

    return bindings;
}

}  // namespace tint::spirv::writer