llvm-pass-helpers.cpp

// This file is a part of Julia. License is MIT: https://julialang.org/license

//
// This file implements common functionality that is useful for the late GC frame
// lowering and final GC intrinsic lowering passes. See the corresponding header
// for docs.

#include "llvm-version.h"

#include <llvm/IR/Function.h>
#include <llvm/IR/Metadata.h>
#include <llvm/IR/Module.h>
#include <llvm/IR/Type.h>

#include <iostream>

#include "codegen_shared.h"
#include "julia_assert.h"
#include "llvm-pass-helpers.h"

using namespace llvm;

extern std::pair<MDNode*,MDNode*> tbaa_make_child(const char *name, MDNode *parent=nullptr, bool isConstant=false);

JuliaPassContext::JuliaPassContext()
    : T_size(nullptr), T_int8(nullptr), T_int32(nullptr),
        T_pint8(nullptr), T_jlvalue(nullptr), T_prjlvalue(nullptr),
        T_ppjlvalue(nullptr), T_pjlvalue(nullptr), T_pjlvalue_der(nullptr),
        T_ppjlvalue_der(nullptr), ptls_getter(nullptr), gc_flush_func(nullptr),
        gc_preserve_begin_func(nullptr), gc_preserve_end_func(nullptr),
        pointer_from_objref_func(nullptr), alloc_obj_func(nullptr),
        typeof_func(nullptr), write_barrier_func(nullptr), module(nullptr)
{
    tbaa_gcframe = tbaa_make_child("jtbaa_gcframe").first;
    MDNode *tbaa_data;
    MDNode *tbaa_data_scalar;
    std::tie(tbaa_data, tbaa_data_scalar) = tbaa_make_child("jtbaa_data");
    tbaa_tag = tbaa_make_child("jtbaa_tag", tbaa_data_scalar).first;
}

void JuliaPassContext::initFunctions(Module &M)
{
    module = &M;

    ptls_getter = M.getFunction("julia.ptls_states");
    gc_flush_func = M.getFunction("julia.gcroot_flush");
    gc_preserve_begin_func = M.getFunction("llvm.julia.gc_preserve_begin");
    gc_preserve_end_func = M.getFunction("llvm.julia.gc_preserve_end");
    pointer_from_objref_func = M.getFunction("julia.pointer_from_objref");
    typeof_func = M.getFunction("julia.typeof");
    write_barrier_func = M.getFunction("julia.write_barrier");
    alloc_obj_func = M.getFunction("julia.gc_alloc_obj");
}

void JuliaPassContext::initAll(Module &M)
{
    // First initialize the functions.
    initFunctions(M);

    // Then initialize types and metadata nodes.
    auto &ctx = M.getContext();
    T_size = M.getDataLayout().getIntPtrType(ctx);
    T_int8 = Type::getInt8Ty(ctx);
    T_pint8 = PointerType::get(T_int8, 0);
    T_int32 = Type::getInt32Ty(ctx);

    // Find 'jl_value_t' by searching through the module's
    // identified struct types. This is a much more robust way
    // to find 'jl_value_t' than an ad-hoc search through
    // intrinsics that may or may not be defined in the module.
    T_jlvalue = nullptr;
    for (auto type : M.getIdentifiedStructTypes()) {
        if (type->hasName() && type->getName() == "jl_value_t") {
            T_jlvalue = type;
            break;
        }
    }

    // If 'jl_value_t' doesn't exist yet then we'll just define it.
    if (!T_jlvalue) {
        T_jlvalue = StructType::create(ctx, "jl_value_t");
    }

    // Construct derived types.
    T_pjlvalue = PointerType::get(T_jlvalue, 0);
    T_prjlvalue = PointerType::get(T_jlvalue, AddressSpace::Tracked);
    T_ppjlvalue = PointerType::get(T_pjlvalue, 0);
    T_pjlvalue_der = PointerType::get(T_jlvalue, AddressSpace::Derived);
    T_ppjlvalue_der = PointerType::get(T_prjlvalue, AddressSpace::Derived);
}

llvm::CallInst *JuliaPassContext::getPtls(llvm::Function &F) const
{
    for (auto I = F.getEntryBlock().begin(), E = F.getEntryBlock().end();
         ptls_getter && I != E; ++I) {
        if (CallInst *callInst = dyn_cast<CallInst>(&*I)) {
            if (callInst->getCalledValue() == ptls_getter) {
                return callInst;
            }
        }
    }
    return nullptr;
}

llvm::Function *JuliaPassContext::getOrNull(
    const jl_intrinsics::IntrinsicDescription &desc) const
{
    return module->getFunction(desc.name);
}

llvm::Function *JuliaPassContext::getOrDeclare(
    const jl_intrinsics::IntrinsicDescription &desc)
{
    auto local = getOrNull(desc);
    if (local) {
        // If the function exists already, then we'll
        // just return it.
        return local;
    }
    else {
        // Otherwise, we'll declare it and add it to the module.
        // Declare the function.
        auto func = desc.declare(*this);
        // Add it to the function list.
        module->getFunctionList().push_back(func);
        // Return the newly created function.
        return func;
    }
}

namespace jl_intrinsics {
    static const char *GET_GC_FRAME_SLOT_NAME = "julia.get_gc_frame_slot";
    static const char *GC_ALLOC_BYTES_NAME = "julia.gc_alloc_bytes";
    static const char *NEW_GC_FRAME_NAME = "julia.new_gc_frame";
    static const char *PUSH_GC_FRAME_NAME = "julia.push_gc_frame";
    static const char *POP_GC_FRAME_NAME = "julia.pop_gc_frame";
    static const char *QUEUE_GC_ROOT_NAME = "julia.queue_gc_root";

    // Annotates a function with attributes suitable for GC allocation
    // functions. Specifically, the return value is marked noalias and nonnull.
    // The allocation size is set to the first argument.
    static Function *addGCAllocAttributes(Function *target, LLVMContext &context)
    {
        target->addAttribute(AttributeList::ReturnIndex, Attribute::NoAlias);
        target->addAttribute(AttributeList::ReturnIndex, Attribute::NonNull);
        target->addFnAttr(Attribute::getWithAllocSizeArgs(context, 1, None)); // returns %1 bytes
        return target;
    }

    const IntrinsicDescription getGCFrameSlot(
        GET_GC_FRAME_SLOT_NAME,
        [](const JuliaPassContext &context) {
            return Function::Create(
                FunctionType::get(
                    PointerType::get(context.T_prjlvalue, 0),
                    {PointerType::get(context.T_prjlvalue, 0), context.T_int32},
                    false),
                Function::ExternalLinkage,
                GET_GC_FRAME_SLOT_NAME);
        });

    const IntrinsicDescription GCAllocBytes(
        GC_ALLOC_BYTES_NAME,
        [](const JuliaPassContext &context) {
            auto intrinsic = Function::Create(
                FunctionType::get(
                    context.T_prjlvalue,
                    { context.T_pint8, context.T_size },
                    false),
                Function::ExternalLinkage,
                GC_ALLOC_BYTES_NAME);

            return addGCAllocAttributes(intrinsic, context.getLLVMContext());
        });

    const IntrinsicDescription newGCFrame(
        NEW_GC_FRAME_NAME,
        [](const JuliaPassContext &context) {
            auto intrinsic = Function::Create(
                FunctionType::get(PointerType::get(context.T_prjlvalue, 0), {context.T_int32}, false),
                Function::ExternalLinkage,
                NEW_GC_FRAME_NAME);
            intrinsic->addAttribute(AttributeList::ReturnIndex, Attribute::NoAlias);
            intrinsic->addAttribute(AttributeList::ReturnIndex, Attribute::NonNull);

            return intrinsic;
        });

    const IntrinsicDescription pushGCFrame(
        PUSH_GC_FRAME_NAME,
        [](const JuliaPassContext &context) {
            return Function::Create(
                FunctionType::get(
                    Type::getVoidTy(context.getLLVMContext()),
                    {PointerType::get(context.T_prjlvalue, 0), context.T_int32},
                    false),
                Function::ExternalLinkage,
                PUSH_GC_FRAME_NAME);
        });

    const IntrinsicDescription popGCFrame(
        POP_GC_FRAME_NAME,
        [](const JuliaPassContext &context) {
            return Function::Create(
                FunctionType::get(
                    Type::getVoidTy(context.getLLVMContext()),
                    {PointerType::get(context.T_prjlvalue, 0)},
                    false),
                Function::ExternalLinkage,
                POP_GC_FRAME_NAME);
        });

    const IntrinsicDescription queueGCRoot(
        QUEUE_GC_ROOT_NAME,
        [](const JuliaPassContext &context) {
            auto intrinsic = Function::Create(
                FunctionType::get(
                    Type::getVoidTy(context.getLLVMContext()),
                    { context.T_prjlvalue },
                    false),
                Function::ExternalLinkage,
                QUEUE_GC_ROOT_NAME);
            intrinsic->addFnAttr(Attribute::InaccessibleMemOrArgMemOnly);
            return intrinsic;
        });
}

namespace jl_well_known {
    static const char *GC_BIG_ALLOC_NAME = "jl_gc_big_alloc";
    static const char *GC_POOL_ALLOC_NAME = "jl_gc_pool_alloc";
    static const char *GC_QUEUE_ROOT_NAME = "jl_gc_queue_root";

    using jl_intrinsics::addGCAllocAttributes;

    const WellKnownFunctionDescription GCBigAlloc(
        GC_BIG_ALLOC_NAME,
        [](const JuliaPassContext &context) {
            auto bigAllocFunc = Function::Create(
                FunctionType::get(
                    context.T_prjlvalue,
                    { context.T_pint8, context.T_size },
                    false),
                Function::ExternalLinkage,
                GC_BIG_ALLOC_NAME);

            return addGCAllocAttributes(bigAllocFunc, context.getLLVMContext());
        });

    const WellKnownFunctionDescription GCPoolAlloc(
        GC_POOL_ALLOC_NAME,
        [](const JuliaPassContext &context) {
            auto poolAllocFunc = Function::Create(
                FunctionType::get(
                    context.T_prjlvalue,
                    { context.T_pint8, context.T_int32, context.T_int32 },
                    false),
                Function::ExternalLinkage,
                GC_POOL_ALLOC_NAME);

            return addGCAllocAttributes(poolAllocFunc, context.getLLVMContext());
        });

    const WellKnownFunctionDescription GCQueueRoot(
        GC_QUEUE_ROOT_NAME,
        [](const JuliaPassContext &context) {
            auto func = Function::Create(
                FunctionType::get(
                    Type::getVoidTy(context.getLLVMContext()),
                    { context.T_prjlvalue },
                    false),
                Function::ExternalLinkage,
                GC_QUEUE_ROOT_NAME);
            func->addFnAttr(Attribute::InaccessibleMemOrArgMemOnly);
            return func;
        });
}