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#include "src/tint/lang/spirv/writer/raise/keep_binding_array_as_pointer.h"

#include "src/tint/lang/core/ir/builder.h"
#include "src/tint/lang/core/ir/module.h"
#include "src/tint/lang/core/ir/validator.h"
#include "src/tint/lang/core/type/binding_array.h"

using namespace tint::core::number_suffixes;  // NOLINT
using namespace tint::core::fluent_types;     // NOLINT

namespace tint::spirv::writer::raise {

namespace {

/// PIMPL state for the transform.
struct State {
    /// The IR module.
    core::ir::Module& ir;

    /// The IR builder.
    core::ir::Builder b{ir};

    /// The type manager.
    core::type::Manager& ty{ir.Types()};

    /// Process the module.
    void Process() {
        // Find the access instructions that need replacing.
        for (auto* inst : ir.Instructions()) {
            auto* load = inst->As<core::ir::Load>();
            if (load == nullptr) {
                continue;
            }

            auto* ba_type = load->Result()->Type()->As<core::type::BindingArray>();
            if (ba_type == nullptr) {
                continue;
            }
            TINT_IR_ASSERT(ir, ba_type->IsHandle());

            auto* ba_ptr = load->From();
            auto* element_ptr_ty = ty.ptr<handle>(ba_type->ElemType());

            load->Result()->ForEachUseUnsorted([&](core::ir::Usage use) {
                Switch(
                    use.instruction,
                    [&](core::ir::Access* access) {
                        b.InsertBefore(access, [&]() {
                            std::span<core::ir::Value* const> indices_span = access->Indices();
                            auto* element_ptr = b.Access(element_ptr_ty, ba_ptr,
                                                         Vector<core::ir::Value*, 1>{indices_span});
                            b.LoadWithResult(access->DetachResult(), element_ptr);
                            access->Destroy();
                        });
                    },
                    TINT_ICE_ON_NO_MATCH);
            });
            load->Destroy();
        }
    }
};

}  // namespace

Result<SuccessType> KeepBindingArrayAsPointer(core::ir::Module& ir) {
    core::ir::AssertValid(ir, kKeepBindingArrayAsPointerCapabilities,
                          "before spirv.KeepBindingArrayAsPointer");

    State{ir}.Process();

    return Success;
}

}  // namespace tint::spirv::writer::raise
