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#include "src/tint/lang/core/ir/transform/vectorize_scalar_matrix_constructors.h"

#include <utility>

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

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

namespace tint::core::ir::transform {

namespace {

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

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

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

    /// Process the module.
    void Process() {
        // Find and replace matrix constructors that take scalar operands.
        Vector<Construct*, 8> worklist;
        for (auto inst : ir.instructions.Objects()) {
            if (auto* construct = inst->As<Construct>(); construct && construct->Alive()) {
                if (construct->Result()->Type()->As<type::Matrix>()) {
                    if (construct->Operands().Length() > 0 &&
                        construct->Operands()[0]->Type()->Is<type::Scalar>()) {
                        b.InsertBefore(construct, [&] {  //
                            ReplaceConstructor(construct);
                        });
                    }
                }
            }
        }
    }

    /// Replace a matrix construct instruction.
    /// @param construct the instruction to replace
    void ReplaceConstructor(Construct* construct) {
        auto* mat = construct->Result()->Type()->As<type::Matrix>();
        auto* col = mat->ColumnType();
        const auto& scalars = construct->Operands();

        // Collect consecutive scalars into column vectors.
        Vector<Value*, 4> columns;
        for (uint32_t c = 0; c < mat->columns(); c++) {
            Vector<Value*, 4> values;
            for (uint32_t r = 0; r < col->Width(); r++) {
                values.Push(scalars[c * col->Width() + r]);
            }
            columns.Push(b.Construct(col, std::move(values))->Result());
        }

        // Construct the matrix from the column vectors and replace the original instruction.
        auto* replacement = b.Construct(mat, std::move(columns))->Result();
        construct->Result()->ReplaceAllUsesWith(replacement);
        construct->Destroy();
    }
};

}  // namespace

Result<SuccessType> VectorizeScalarMatrixConstructors(Module& ir) {
    auto result = ValidateAndDumpIfNeeded(ir, "VectorizeScalarMatrixConstructors transform");
    if (!result) {
        return result;
    }

    State{ir}.Process();

    return Success;
}

}  // namespace tint::core::ir::transform