luau/CodeGen/src/CodeGen.cpp

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#include "Luau/CodeGen.h"

#include "Luau/AssemblyBuilderX64.h"
#include "Luau/Common.h"
#include "Luau/CodeAllocator.h"
#include "Luau/CodeBlockUnwind.h"
#include "Luau/IrAnalysis.h"
#include "Luau/IrBuilder.h"
#include "Luau/OptimizeConstProp.h"
#include "Luau/OptimizeFinalX64.h"
#include "Luau/UnwindBuilder.h"
#include "Luau/UnwindBuilderDwarf2.h"
#include "Luau/UnwindBuilderWin.h"

#include "CustomExecUtils.h"
#include "CodeGenX64.h"
#include "EmitCommonX64.h"
#include "EmitInstructionX64.h"
#include "IrLoweringX64.h"
#include "NativeState.h"

#include "lapi.h"

#include <memory>

#if defined(__x86_64__) || defined(_M_X64)
#ifdef _MSC_VER
#include <intrin.h> // __cpuid
#else
#include <cpuid.h> // __cpuid
#endif
#endif

LUAU_FASTFLAGVARIABLE(DebugCodegenNoOpt, false)

namespace Luau
{
namespace CodeGen
{

constexpr uint32_t kFunctionAlignment = 32;

static void assembleHelpers(X64::AssemblyBuilderX64& build, ModuleHelpers& helpers)
{
    if (build.logText)
        build.logAppend("; exitContinueVm\n");
    helpers.exitContinueVm = build.setLabel();
    emitExit(build, /* continueInVm */ true);

    if (build.logText)
        build.logAppend("; exitNoContinueVm\n");
    helpers.exitNoContinueVm = build.setLabel();
    emitExit(build, /* continueInVm */ false);

    if (build.logText)
        build.logAppend("; continueCallInVm\n");
    helpers.continueCallInVm = build.setLabel();
    emitContinueCallInVm(build);
}

static NativeProto* assembleFunction(X64::AssemblyBuilderX64& build, NativeState& data, ModuleHelpers& helpers, Proto* proto, AssemblyOptions options)
{
    NativeProto* result = new NativeProto();

    result->proto = proto;

    if (options.includeAssembly || options.includeIr)
    {
        if (proto->debugname)
            build.logAppend("; function %s(", getstr(proto->debugname));
        else
            build.logAppend("; function(");

        for (int i = 0; i < proto->numparams; i++)
        {
            LocVar* var = proto->locvars ? &proto->locvars[proto->sizelocvars - proto->numparams + i] : nullptr;

            if (var && var->varname)
                build.logAppend("%s%s", i == 0 ? "" : ", ", getstr(var->varname));
            else
                build.logAppend("%s$arg%d", i == 0 ? "" : ", ", i);
        }

        if (proto->numparams != 0 && proto->is_vararg)
            build.logAppend(", ...)");
        else
            build.logAppend(")");

        if (proto->linedefined >= 0)
            build.logAppend(" line %d\n", proto->linedefined);
        else
            build.logAppend("\n");
    }

    build.align(kFunctionAlignment, X64::AlignmentDataX64::Ud2);

    Label start = build.setLabel();

    IrBuilder builder;
    builder.buildFunctionIr(proto);

    if (!FFlag::DebugCodegenNoOpt)
    {
        constPropInBlockChains(builder);
    }

    // TODO: cfg info has to be computed earlier to use in optimizations
    // It's done here to appear in text output and to measure performance impact on code generation
    computeCfgInfo(builder.function);

    optimizeMemoryOperandsX64(builder.function);

    X64::IrLoweringX64 lowering(build, helpers, data, proto, builder.function);

    lowering.lower(options);

    result->instTargets = new uintptr_t[proto->sizecode];

    for (int i = 0; i < proto->sizecode; i++)
    {
        auto [irLocation, asmLocation] = builder.function.bcMapping[i];

        result->instTargets[i] = irLocation == ~0u ? 0 : asmLocation - start.location;
    }

    result->location = start.location;

    if (build.logText)
        build.logAppend("\n");

    return result;
}

static void destroyNativeProto(NativeProto* nativeProto)
{
    delete[] nativeProto->instTargets;
    delete nativeProto;
}

static void onCloseState(lua_State* L)
{
    destroyNativeState(L);
}

static void onDestroyFunction(lua_State* L, Proto* proto)
{
    NativeProto* nativeProto = getProtoExecData(proto);
    LUAU_ASSERT(nativeProto->proto == proto);

    setProtoExecData(proto, nullptr);
    destroyNativeProto(nativeProto);
}

static int onEnter(lua_State* L, Proto* proto)
{
    if (L->singlestep)
        return 1;

    NativeState* data = getNativeState(L);

    if (!L->ci->savedpc)
        L->ci->savedpc = proto->code;

    // We will jump into native code through a gateway
    bool (*gate)(lua_State*, Proto*, uintptr_t, NativeContext*) = (bool (*)(lua_State*, Proto*, uintptr_t, NativeContext*))data->context.gateEntry;

    NativeProto* nativeProto = getProtoExecData(proto);
    uintptr_t target = nativeProto->instTargets[L->ci->savedpc - proto->code];

    // Returns 1 to finish the function in the VM
    return gate(L, proto, target, &data->context);
}

static void onSetBreakpoint(lua_State* L, Proto* proto, int instruction)
{
    if (!getProtoExecData(proto))
        return;

    LUAU_ASSERT(!"native breakpoints are not implemented");
}

bool isSupported()
{
#if !LUA_CUSTOM_EXECUTION
    return false;
#elif defined(__x86_64__) || defined(_M_X64)
    if (LUA_EXTRA_SIZE != 1)
        return false;

    if (sizeof(TValue) != 16)
        return false;

    if (sizeof(LuaNode) != 32)
        return false;

    int cpuinfo[4] = {};
#ifdef _MSC_VER
    __cpuid(cpuinfo, 1);
#else
    __cpuid(1, cpuinfo[0], cpuinfo[1], cpuinfo[2], cpuinfo[3]);
#endif

    // We require AVX1 support for VEX encoded XMM operations
    // We also requre SSE4.1 support for ROUNDSD but the AVX check below covers it
    // https://en.wikipedia.org/wiki/CPUID#EAX=1:_Processor_Info_and_Feature_Bits
    if ((cpuinfo[2] & (1 << 28)) == 0)
        return false;

    return true;
#else
    return false;
#endif
}

void create(lua_State* L)
{
    LUAU_ASSERT(isSupported());

    NativeState& data = *createNativeState(L);

#if defined(_WIN32)
    data.unwindBuilder = std::make_unique<UnwindBuilderWin>();
#else
    data.unwindBuilder = std::make_unique<UnwindBuilderDwarf2>();
#endif

    data.codeAllocator.context = data.unwindBuilder.get();
    data.codeAllocator.createBlockUnwindInfo = createBlockUnwindInfo;
    data.codeAllocator.destroyBlockUnwindInfo = destroyBlockUnwindInfo;

    initFallbackTable(data);
    initHelperFunctions(data);

    if (!X64::initEntryFunction(data))
    {
        destroyNativeState(L);
        return;
    }

    lua_ExecutionCallbacks* ecb = getExecutionCallbacks(L);

    ecb->close = onCloseState;
    ecb->destroy = onDestroyFunction;
    ecb->enter = onEnter;
    ecb->setbreakpoint = onSetBreakpoint;
}

static void gatherFunctions(std::vector<Proto*>& results, Proto* proto)
{
    if (results.size() <= size_t(proto->bytecodeid))
        results.resize(proto->bytecodeid + 1);

    // Skip protos that we've already compiled in this run: this happens because at -O2, inlined functions get their protos reused
    if (results[proto->bytecodeid])
        return;

    results[proto->bytecodeid] = proto;

    for (int i = 0; i < proto->sizep; i++)
        gatherFunctions(results, proto->p[i]);
}

void compile(lua_State* L, int idx)
{
    LUAU_ASSERT(lua_isLfunction(L, idx));
    const TValue* func = luaA_toobject(L, idx);

    // If initialization has failed, do not compile any functions
    if (!getNativeState(L))
        return;

    X64::AssemblyBuilderX64 build(/* logText= */ false);
    NativeState* data = getNativeState(L);

    std::vector<Proto*> protos;
    gatherFunctions(protos, clvalue(func)->l.p);

    ModuleHelpers helpers;
    assembleHelpers(build, helpers);

    std::vector<NativeProto*> results;
    results.reserve(protos.size());

    // Skip protos that have been compiled during previous invocations of CodeGen::compile
    for (Proto* p : protos)
        if (p && getProtoExecData(p) == nullptr)
            results.push_back(assembleFunction(build, *data, helpers, p, {}));

    build.finalize();

    uint8_t* nativeData = nullptr;
    size_t sizeNativeData = 0;
    uint8_t* codeStart = nullptr;
    if (!data->codeAllocator.allocate(
            build.data.data(), int(build.data.size()), build.code.data(), int(build.code.size()), nativeData, sizeNativeData, codeStart))
    {
        for (NativeProto* result : results)
            destroyNativeProto(result);

        return;
    }

    // Relocate instruction offsets
    for (NativeProto* result : results)
    {
        for (int i = 0; i < result->proto->sizecode; i++)
            result->instTargets[i] += uintptr_t(codeStart + result->location);

        LUAU_ASSERT(result->proto->sizecode);
        result->entryTarget = result->instTargets[0];
    }

    // Link native proto objects to Proto; the memory is now managed by VM and will be freed via onDestroyFunction
    for (NativeProto* result : results)
        setProtoExecData(result->proto, result);
}

std::string getAssembly(lua_State* L, int idx, AssemblyOptions options)
{
    LUAU_ASSERT(lua_isLfunction(L, idx));
    const TValue* func = luaA_toobject(L, idx);

    X64::AssemblyBuilderX64 build(/* logText= */ options.includeAssembly);

    NativeState data;
    initFallbackTable(data);

    std::vector<Proto*> protos;
    gatherFunctions(protos, clvalue(func)->l.p);

    ModuleHelpers helpers;
    assembleHelpers(build, helpers);

    for (Proto* p : protos)
        if (p)
        {
            NativeProto* nativeProto = assembleFunction(build, data, helpers, p, options);
            destroyNativeProto(nativeProto);
        }

    build.finalize();

    if (options.outputBinary)
        return std::string(build.code.begin(), build.code.end()) + std::string(build.data.begin(), build.data.end());
    else
        return build.text;
}

} // namespace CodeGen
} // namespace Luau