ClickHouse/dbms/src/Interpreters/ExpressionJIT.cpp

#include <Columns/ColumnConst.h>
#include <Columns/ColumnVector.h>
#include <Common/typeid_cast.h>
#include <DataTypes/DataTypeNullable.h>
#include <DataTypes/DataTypesNumber.h>
#include <Interpreters/ExpressionJIT.h>

#include <llvm/IR/BasicBlock.h>
#include <llvm/IR/DataLayout.h>
#include <llvm/IR/DerivedTypes.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/IRBuilder.h>
#include <llvm/IR/LLVMContext.h>
#include <llvm/IR/Mangler.h>
#include <llvm/IR/Module.h>
#include <llvm/IR/Type.h>
#include <llvm/IR/Verifier.h>
#include <llvm/ExecutionEngine/ExecutionEngine.h>
#include <llvm/ExecutionEngine/JITSymbol.h>
#include <llvm/ExecutionEngine/SectionMemoryManager.h>
#include <llvm/ExecutionEngine/Orc/CompileUtils.h>
#include <llvm/ExecutionEngine/Orc/IRCompileLayer.h>
#include <llvm/ExecutionEngine/Orc/NullResolver.h>
#include <llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h>
#include <llvm/Support/TargetSelect.h>
#include <llvm/Support/raw_ostream.h>
#include <llvm/Target/TargetMachine.h>
#include <llvm/Transforms/IPO/PassManagerBuilder.h>

#include <stdexcept>

namespace DB
{

namespace ErrorCodes
{
    extern const int LOGICAL_ERROR;
}

template <typename T>
static bool typeIsA(const DataTypePtr & type)
{
    return typeid_cast<const T *>(removeNullable(type).get());;
}

struct LLVMContext::Data
{
    llvm::LLVMContext context;
    std::shared_ptr<llvm::Module> module;
    std::unique_ptr<llvm::TargetMachine> machine;
    llvm::orc::RTDyldObjectLinkingLayer objectLayer;
    llvm::orc::IRCompileLayer<decltype(objectLayer), llvm::orc::SimpleCompiler> compileLayer;
    llvm::DataLayout layout;
    llvm::IRBuilder<> builder;

    Data()
        : module(std::make_shared<llvm::Module>("jit", context))
        , machine(llvm::EngineBuilder().selectTarget())
        , objectLayer([]() { return std::make_shared<llvm::SectionMemoryManager>(); })
        , compileLayer(objectLayer, llvm::orc::SimpleCompiler(*machine))
        , layout(machine->createDataLayout())
        , builder(context)
    {
        module->setDataLayout(layout);
        module->setTargetTriple(machine->getTargetTriple().getTriple());
    }

    llvm::Type * toNativeType(const DataTypePtr & type)
    {
        /// LLVM doesn't have unsigned types, it has unsigned instructions.
        if (typeIsA<DataTypeInt8>(type) || typeIsA<DataTypeUInt8>(type))
            return builder.getInt8Ty();
        if (typeIsA<DataTypeInt16>(type) || typeIsA<DataTypeUInt16>(type))
            return builder.getInt16Ty();
        if (typeIsA<DataTypeInt32>(type) || typeIsA<DataTypeUInt32>(type))
            return builder.getInt32Ty();
        if (typeIsA<DataTypeInt64>(type) || typeIsA<DataTypeUInt64>(type))
            return builder.getInt64Ty();
        if (typeIsA<DataTypeFloat32>(type))
            return builder.getFloatTy();
        if (typeIsA<DataTypeFloat64>(type))
            return builder.getDoubleTy();
        return nullptr;
    }

    LLVMCompiledFunction * lookup(const std::string& name)
    {
        std::string mangledName;
        llvm::raw_string_ostream mangledNameStream(mangledName);
        llvm::Mangler::getNameWithPrefix(mangledNameStream, name, layout);
        /// why is `findSymbol` not const? we may never know.
        return reinterpret_cast<LLVMCompiledFunction *>(compileLayer.findSymbol(mangledNameStream.str(), false).getAddress().get());
    }
};

LLVMContext::LLVMContext()
    : shared(std::make_shared<LLVMContext::Data>())
{}

void LLVMContext::finalize()
{
    if (!shared->module->size())
        return;
    shared->module->print(llvm::errs(), nullptr, false, true);
    llvm::PassManagerBuilder builder;
    llvm::legacy::FunctionPassManager fpm(shared->module.get());
    builder.OptLevel = 2;
    builder.populateFunctionPassManager(fpm);
    for (auto & function : *shared->module)
        fpm.run(function);
    llvm::cantFail(shared->compileLayer.addModule(shared->module, std::make_shared<llvm::orc::NullResolver>()));
    shared->module->print(llvm::errs(), nullptr, false, true);
}

bool LLVMContext::isCompilable(const IFunctionBase& function) const
{
    if (!function.isCompilable() || !shared->toNativeType(function.getReturnType()))
        return false;
    for (const auto & type : function.getArgumentTypes())
        if (!shared->toNativeType(type))
            return false;
    return true;
}

LLVMPreparedFunction::LLVMPreparedFunction(LLVMContext context, std::shared_ptr<const IFunctionBase> parent)
    : parent(parent), context(context), function(context->lookup(parent->getName()))
{}

void LLVMPreparedFunction::executeImpl(Block & block, const ColumnNumbers & arguments, size_t result)
{
    /// assuming that the function has default behavior on NULL, the column will be wrapped by `PreparedFunctionImpl::execute`.
    size_t block_size = block.rows();
    auto col_res = removeNullable(parent->getReturnType())->createColumn()->cloneResized(block_size);
    if (block_size)
    {
        std::vector<const void *> columns(arguments.size());
        std::vector<char> is_const(arguments.size());
        for (size_t i = 0; i < arguments.size(); i++)
        {
            auto * column = block.getByPosition(arguments[i]).column.get();
            if (!column)
                throw Exception("column " + block.getByPosition(arguments[i]).name + " is missing", ErrorCodes::LOGICAL_ERROR);
            if (!column->isFixedAndContiguous())
                throw Exception("column type " + column->getName() + " is not a contiguous array; its data type "
                                "should've had no native equivalent in LLVMContext::Data::toNativeType", ErrorCodes::LOGICAL_ERROR);
            columns[i] = column->getRawData().data;
            is_const[i] = column->isColumnConst();
        }
        function(columns.data(), is_const.data(), const_cast<char *>(col_res->getRawData().data), block_size);
    }
    block.getByPosition(result).column = std::move(col_res);
};

LLVMFunction::LLVMFunction(ExpressionActions::Actions actions_, LLVMContext context)
    : actions(std::move(actions_)), context(context)
{
    std::unordered_set<std::string> seen;
    for (const auto & action : actions)
    {
        const auto & names = action.argument_names;
        const auto & types = action.function->getArgumentTypes();
        for (size_t i = 0; i < names.size(); i++)
        {
            if (seen.emplace(names[i]).second)
            {
                arg_names.push_back(names[i]);
                arg_types.push_back(types[i]);
            }
        }
        seen.insert(action.result_name);
    }

    llvm::FunctionType * func_type = llvm::FunctionType::get(context->builder.getVoidTy(), {
        llvm::PointerType::getUnqual(llvm::PointerType::getUnqual(context->builder.getVoidTy())),
        llvm::PointerType::getUnqual(context->builder.getInt8Ty()),
        llvm::PointerType::getUnqual(context->toNativeType(actions.back().function->getReturnType())),
        context->builder.getIntNTy(sizeof(size_t) * 8),
    }, /*isVarArg=*/false);
    auto * func = llvm::Function::Create(func_type, llvm::Function::ExternalLinkage, actions.back().result_name, context->module.get());
    auto args = func->args().begin();
    llvm::Value * inputs = &*args++; /// void** - tuple of columns, each a contiguous data block
    llvm::Value * consts = &*args++; /// char* - for each column, 0 if it is full, 1 if it points to a single constant value
    llvm::Value * output = &*args++; /// void* - space for the result
    llvm::Value * counter = &*args++; /// size_t - number of entries to read from non-const values and write to output

    auto * entry = llvm::BasicBlock::Create(context->context, "entry", func);
    context->builder.SetInsertPoint(entry);

    std::vector<llvm::Value *> inputs_v(arg_types.size());
    std::vector<llvm::Value *> deltas_v(arg_types.size());
    for (size_t i = 0; i < arg_types.size(); i++)
    {
        if (i != 0)
        {
            inputs = context->builder.CreateConstGEP1_32(inputs, 1);
            consts = context->builder.CreateConstGEP1_32(consts, 1);
        }
        auto * type = llvm::PointerType::getUnqual(context->toNativeType(arg_types[i]));
        auto * step = context->builder.CreateICmpEQ(context->builder.CreateLoad(consts), llvm::ConstantInt::get(context->builder.getInt8Ty(), 0));
        inputs_v[i] = context->builder.CreatePointerCast(context->builder.CreateLoad(inputs), type);
        deltas_v[i] = context->builder.CreateZExt(step, context->builder.getInt32Ty());
    }

    /// assume nonzero initial value in `counter`
    auto * loop = llvm::BasicBlock::Create(context->context, "loop", func);
    context->builder.CreateBr(loop);
    context->builder.SetInsertPoint(loop);

    std::unordered_map<std::string, std::function<llvm::Value * ()>> by_name;
    std::vector<llvm::PHINode *> phi(inputs_v.size());
    for (size_t i = 0; i < inputs_v.size(); i++)
    {
        phi[i] = context->builder.CreatePHI(inputs_v[i]->getType(), 2);
        phi[i]->addIncoming(inputs_v[i], entry);
    }
    auto * output_phi = context->builder.CreatePHI(output->getType(), 2);
    auto * counter_phi = context->builder.CreatePHI(counter->getType(), 2);
    output_phi->addIncoming(output, entry);
    counter_phi->addIncoming(counter, entry);

    for (size_t i = 0; i < phi.size(); i++)
        if (!by_name.emplace(arg_names[i], [&, i]() { return context->builder.CreateLoad(phi[i]); }).second)
            throw Exception("duplicate input column name", ErrorCodes::LOGICAL_ERROR);
    for (const auto & action : actions)
    {
        ValuePlaceholders action_input;
        action_input.reserve(action.argument_names.size());
        for (const auto & name : action.argument_names)
            action_input.push_back(by_name.at(name));
        auto generator = [&action, &context, action_input{std::move(action_input)}]()
        {
            return action.function->compile(context->builder, action_input);
        };
        if (!by_name.emplace(action.result_name, std::move(generator)).second)
            throw Exception("duplicate action result name", ErrorCodes::LOGICAL_ERROR);
    }
    context->builder.CreateStore(by_name.at(actions.back().result_name)(), output_phi);

    auto * cur_block = context->builder.GetInsertBlock();
    for (size_t i = 0; i < phi.size(); i++)
        phi[i]->addIncoming(context->builder.CreateGEP(phi[i], deltas_v[i]), cur_block);
    output_phi->addIncoming(context->builder.CreateConstGEP1_32(output_phi, 1), cur_block);
    counter_phi->addIncoming(context->builder.CreateSub(counter_phi, llvm::ConstantInt::get(counter_phi->getType(), 1)), cur_block);

    auto * end = llvm::BasicBlock::Create(context->context, "end", func);
    context->builder.CreateCondBr(context->builder.CreateICmpNE(counter_phi, llvm::ConstantInt::get(counter_phi->getType(), 1)), loop, end);
    context->builder.SetInsertPoint(end);
    context->builder.CreateRetVoid();
}

static Field evaluateFunction(IFunctionBase & function, const IDataType & type, const Field & arg)
{
    const auto & arg_types = function.getArgumentTypes();
    if (arg_types.size() != 1 || !arg_types[0]->equals(type))
        return {};
    auto column = arg_types[0]->createColumn();
    column->insert(arg);
    Block block = {{ ColumnConst::create(std::move(column), 1), arg_types[0], "_arg" }, { nullptr, function.getReturnType(), "_result" }};
    function.execute(block, {0}, 1);
    auto result = block.getByPosition(1).column;
    return result && result->size() == 1 ? (*result)[0] : Field();
}

IFunctionBase::Monotonicity LLVMFunction::getMonotonicityForRange(const IDataType & type, const Field & left, const Field & right) const
{
    const IDataType * type_ = &type;
    Field left_ = left;
    Field right_ = right;
    Monotonicity result(true, true, true);
    /// monotonicity is only defined for unary functions, to the chain must describe a sequence of nested calls
    for (size_t i = 0; i < actions.size(); i++)
    {
        Monotonicity m = actions[i].function->getMonotonicityForRange(type, left_, right_);
        if (!m.is_monotonic)
            return m;
        result.is_positive ^= !m.is_positive;
        result.is_always_monotonic &= m.is_always_monotonic;
        if (i + 1 < actions.size())
        {
            if (left_ != Field())
                left_ = evaluateFunction(*actions[i].function, *type_, left_);
            if (right_ != Field())
                right_ = evaluateFunction(*actions[i].function, *type_, right_);
            if (!m.is_positive)
                std::swap(left_, right_);
            type_ = actions[i].function->getReturnType().get();
        }
    }
    return result;
}

}


namespace
{

struct LLVMTargetInitializer
{
    LLVMTargetInitializer()
    {
        llvm::InitializeNativeTarget();
        llvm::InitializeNativeTargetAsmPrinter();
    }
};

}

static LLVMTargetInitializer llvmInitializer;