//===-- nested.cpp --------------------------------------------------------===//
//
//                         LDC – the LLVM D compiler
//
// This file is distributed under the BSD-style LDC license. See the LICENSE
// file for details.
//
//===----------------------------------------------------------------------===//

#include "target.h"
#include "gen/nested.h"
#include "gen/dvalue.h"
#include "gen/functions.h"
#include "gen/irstate.h"
#include "gen/llvmhelpers.h"
#include "gen/logger.h"
#include "gen/tollvm.h"
#include "ir/irfunction.h"
#include "ir/irtypeaggr.h"
#include "llvm/Analysis/ValueTracking.h"

/****************************************************************************************/
/*////////////////////////////////////////////////////////////////////////////////////////
// NESTED VARIABLE HELPERS
////////////////////////////////////////////////////////////////////////////////////////*/

static void storeVariable(VarDeclaration *vd, LLValue *dst)
{
    LLValue *value = getIrLocal(vd)->value;
    int ty = vd->type->ty;
    FuncDeclaration *fd = getParentFunc(vd, true);
    assert(fd && "No parent function for nested variable?");
    if (fd->needsClosure() && !vd->isRef() && (ty == Tstruct || ty == Tsarray) && isaPointer(value->getType())) {
        // Copy structs and static arrays
        LLValue *mem = DtoGcMalloc(vd->loc, DtoType(vd->type), ".gc_mem");
        DtoAggrCopy(mem, value);
        DtoAlignedStore(mem, dst);
    } else
    // Store the address into the frame
    DtoAlignedStore(value, dst);
}

static unsigned getVthisIdx(AggregateDeclaration* ad)
{
    return getFieldGEPIndex(ad, ad->vthis);
}

static void DtoCreateNestedContextType(FuncDeclaration* fd);

DValue* DtoNestedVariable(Loc& loc, Type* astype, VarDeclaration* vd, bool byref)
{
    IF_LOG Logger::println("DtoNestedVariable for %s @ %s", vd->toChars(), loc.toChars());
    LOG_SCOPE;

    ////////////////////////////////////
    // Locate context value

    Dsymbol* vdparent = vd->toParent2();
    assert(vdparent);

    IrFunction* irfunc = gIR->func();

    // Check whether we can access the needed frame
    FuncDeclaration *fd = irfunc->decl;
    while (fd != vdparent) {
        if (fd->isStatic()) {
            error(loc, "function %s cannot access frame of function %s", irfunc->decl->toPrettyChars(), vdparent->toPrettyChars());
            return new DVarValue(astype, vd, llvm::UndefValue::get(DtoPtrToType(astype)));
        }
        fd = getParentFunc(fd, false);
        assert(fd);
    }

    // is the nested variable in this scope?
    if (vdparent == irfunc->decl)
    {
        LLValue* val = getIrValue(vd);
        return new DVarValue(astype, vd, val);
    }

    LLValue *dwarfValue = 0;
#if LDC_LLVM_VER >= 306
    std::vector<int64_t> dwarfAddr;
#else
    std::vector<LLValue*> dwarfAddr;
#endif

    // get the nested context
    LLValue* ctx = 0;
    if (irfunc->nestedVar) {
        // If this function has its own nested context struct, always load it.
        ctx = irfunc->nestedVar;
        dwarfValue = ctx;
    } else if (irfunc->decl->isMember2()) {
        // If this is a member function of a nested class without its own
        // context, load the vthis member.
        AggregateDeclaration* cd = irfunc->decl->isMember2();
        LLValue* val = irfunc->thisArg;
        if (cd->isClassDeclaration())
            val = DtoLoad(val);
        ctx = DtoLoad(DtoGEPi(val, 0, getVthisIdx(cd), ".vthis"));
    } else {
        // Otherwise, this is a simple nested function, load from the context
        // argument.
        ctx = DtoLoad(irfunc->nestArg);
        dwarfValue = irfunc->nestArg;
        if (global.params.symdebug)
            gIR->DBuilder.OpDeref(dwarfAddr);
    }
    assert(ctx);

    DtoCreateNestedContextType(vdparent->isFuncDeclaration());
    assert(isIrLocalCreated(vd));

    ////////////////////////////////////
    // Extract variable from nested context

    LLValue* val = DtoBitCast(ctx, LLPointerType::getUnqual(irfunc->frameType));
    IF_LOG {
        Logger::cout() << "Context: " << *val << '\n';
        Logger::cout() << "of type: " << *irfunc->frameType << '\n';
    }

    unsigned vardepth = getIrLocal(vd)->nestedDepth;
    unsigned funcdepth = irfunc->depth;

    IF_LOG {
        Logger::cout() << "Variable: " << vd->toChars() << '\n';
        Logger::cout() << "Variable depth: " << vardepth << '\n';
        Logger::cout() << "Function: " << irfunc->decl->toChars() << '\n';
        Logger::cout() << "Function depth: " << funcdepth << '\n';
    }

    if (vardepth == funcdepth) {
        // This is not always handled above because functions without
        // variables accessed by nested functions don't create new frames.
        IF_LOG Logger::println("Same depth");
    } else {
        // Load frame pointer and index that...
        if (dwarfValue && global.params.symdebug) {
            gIR->DBuilder.OpOffset(dwarfAddr, val, vardepth);
            gIR->DBuilder.OpDeref(dwarfAddr);
        }
        IF_LOG Logger::println("Lower depth");
        val = DtoGEPi(val, 0, vardepth);
        IF_LOG Logger::cout() << "Frame index: " << *val << '\n';
        val = DtoAlignedLoad(val, (std::string(".frame.") + vdparent->toChars()).c_str());
        IF_LOG Logger::cout() << "Frame: " << *val << '\n';
    }

    int idx = getIrLocal(vd)->nestedIndex;
    assert(idx != -1 && "Nested context not yet resolved for variable.");

    if (dwarfValue && global.params.symdebug)
        gIR->DBuilder.OpOffset(dwarfAddr, val, idx);

    val = DtoGEPi(val, 0, idx, vd->toChars());
    IF_LOG {
        Logger::cout() << "Addr: " << *val << '\n';
        Logger::cout() << "of type: " << *val->getType() << '\n';
    }
    if (byref || (vd->isParameter() && getIrParameter(vd)->arg && getIrParameter(vd)->arg->byref)) {
        val = DtoAlignedLoad(val);
        //dwarfOpDeref(dwarfAddr);
        IF_LOG {
            Logger::cout() << "Was byref, now: " << *val << '\n';
            Logger::cout() << "of type: " << *val->getType() << '\n';
        }
    }

    if (dwarfValue && global.params.symdebug)
        gIR->DBuilder.EmitLocalVariable(dwarfValue, vd, 0, false, dwarfAddr);

    return new DVarValue(astype, vd, val);
}

void DtoResolveNestedContext(Loc& loc, AggregateDeclaration *decl, LLValue *value)
{
    IF_LOG Logger::println("Resolving nested context");
    LOG_SCOPE;

    // get context
    LLValue* nest = DtoNestedContext(loc, decl);

    // store into right location
    if (!llvm::dyn_cast<llvm::UndefValue>(nest)) {
        // Need to make sure the declaration has already been resolved, because
        // when multiple source files are specified on the command line, the
        // frontend sometimes adds "nested" (i.e. a template in module B
        // instantiated from module A with a type from module A instantiates
        // another template from module B) into the wrong module, messing up
        // our codegen order.
        DtoResolveDsymbol(decl);

        unsigned idx = getVthisIdx(decl);
        LLValue* gep = DtoGEPi(value,0,idx,".vthis");
        DtoStore(DtoBitCast(nest, gep->getType()->getContainedType(0)), gep);
    }
}

LLValue* DtoNestedContext(Loc& loc, Dsymbol* sym)
{
    IF_LOG Logger::println("DtoNestedContext for %s", sym->toPrettyChars());
    LOG_SCOPE;

    // Exit quickly for functions that accept a context pointer for ABI purposes,
    // but do not actually read from it.
    //
    // We cannot simply fall back to retuning undef once we discover that we
    // don't actually have a context to pass, because we sadly also need to
    // catch invalid code here in the glue layer (see error() below).
    if (FuncDeclaration* symfd = sym->isFuncDeclaration())
    {
        // Make sure we've had a chance to analyze nested context usage
        DtoCreateNestedContextType(symfd);

        int depth = getIrFunc(symfd)->depth;
        Logger::println("for function of depth %d", depth);
        if (depth == -1 || (depth == 0 && !symfd->closureVars.empty()))
        {
            Logger::println("function does not have context or creates its own "
                "from scratch, returning undef");
            return llvm::UndefValue::get(getVoidPtrType());
        }
    }

    // The function we are currently in, and the constructed object/called
    // function might inherit a context pointer from.
    IrFunction* irfunc = gIR->func();

    bool fromParent = true;

    LLValue* val;
    if (irfunc->nestedVar)
    {
        // if this func has its own vars that are accessed by nested funcs
        // use its own context
        val = irfunc->nestedVar;
        fromParent = false;
    }
    else if (irfunc->nestArg)
    {
        // otherwise, it may have gotten a context from the caller
        val = DtoLoad(irfunc->nestArg);
    }
    else if (irfunc->thisArg)
    {
        // or just have a this argument
        AggregateDeclaration* ad = irfunc->decl->isMember2();
        val = ad->isClassDeclaration() ? DtoLoad(irfunc->thisArg) : irfunc->thisArg;
        if (!ad->vthis)
        {
            // This is just a plain 'outer' reference of a class nested in a
            // function (but without any variables in the nested context).
            return val;
        }
        val = DtoLoad(DtoGEPi(val, 0, getVthisIdx(ad), ".vthis"));
    }
    else
    {
        if (sym->isFuncDeclaration())
        {
            // If we are here, the function actually needs its nested context
            // and we cannot provide one. Thus, it's invalid code that is
            // unfortunately not caught in the frontend (e.g. a function literal
            // tries to call a nested function from the parent scope).
            error(loc, "function %s is a nested function and cannot be accessed from %s",
                sym->toPrettyChars(), irfunc->decl->toPrettyChars());
            fatal();
        }

        // Use null instead of e.g. LLVM's undef to not break bitwise
        // comparison for instances of nested struct types which don't have any
        // nested references.
        return llvm::ConstantPointerNull::get(getVoidPtrType());
    }

    FuncDeclaration* frameToPass = 0;
    if (AggregateDeclaration *ad = sym->isAggregateDeclaration()) {
        // If sym is a nested struct or a nested class, pass the frame
        // of the function where sym is declared.
        frameToPass = ad->toParent()->isFuncDeclaration();
    } else if (FuncDeclaration* symfd = sym->isFuncDeclaration()) {
        // If sym is a nested function, and its parent context is different
        // than the one we got, adjust it.
        frameToPass = getParentFunc(symfd, true);
    }

    if (frameToPass) {
        IF_LOG Logger::println("Parent frame is from %s", frameToPass->toChars());
        FuncDeclaration* ctxfd = irfunc->decl;
        IF_LOG Logger::println("Current function is %s", ctxfd->toChars());
        if (fromParent) {
            ctxfd = getParentFunc(ctxfd, true);
            assert(ctxfd && "Context from outer function, but no outer function?");
        }
        IF_LOG Logger::println("Context is from %s", ctxfd->toChars());

        unsigned neededDepth = getIrFunc(frameToPass)->depth;
        unsigned ctxDepth = getIrFunc(ctxfd)->depth;

        IF_LOG {
            Logger::cout() << "Needed depth: " << neededDepth << '\n';
            Logger::cout() << "Context depth: " << ctxDepth << '\n';
        }

        if (neededDepth >= ctxDepth) {
            // assert(neededDepth <= ctxDepth + 1 && "How are we going more than one nesting level up?");
            // fd needs the same context as we do, so all is well
            IF_LOG Logger::println("Calling sibling function or directly nested function");
        } else {
            val = DtoBitCast(val, LLPointerType::getUnqual(getIrFunc(ctxfd)->frameType));
            val = DtoGEPi(val, 0, neededDepth);
            val = DtoAlignedLoad(val,
                (std::string(".frame.") + frameToPass->toChars()).c_str());
        }
    }

    IF_LOG {
        Logger::cout() << "result = " << *val << '\n';
        Logger::cout() << "of type " << *val->getType() << '\n';
    }
    return val;
}

static void DtoCreateNestedContextType(FuncDeclaration* fd)
{
    IF_LOG Logger::println("DtoCreateNestedContextType for %s", fd->toPrettyChars());
    LOG_SCOPE

    DtoDeclareFunction(fd);

    IrFunction& irFunc = *getIrFunc(fd);

    if (irFunc.nestedContextCreated)
        return;
    irFunc.nestedContextCreated = true;

    FuncDeclaration* parentFunc = getParentFunc(fd, true);
    // Make sure the parent has already been analyzed.
    if (parentFunc)
        DtoCreateNestedContextType(parentFunc);

    // construct nested variables array
    if (fd->closureVars.dim > 0)
    {
        Logger::println("has nested frame");
        // start with adding all enclosing parent frames until a static parent is reached

        LLStructType* innerFrameType = NULL;
        unsigned depth = 0;

        if (parentFunc)
        {
            IrFunction& parentIrFunc = *getIrFunc(parentFunc);
            innerFrameType = parentIrFunc.frameType;
            if (innerFrameType)
                depth = parentIrFunc.depth + 1;
        }

        irFunc.depth = depth;

        IF_LOG Logger::cout() << "Function " << fd->toChars() << " has depth " << depth << '\n';

        AggrTypeBuilder builder(false);

        if (depth != 0)
        {
            assert(innerFrameType);
            unsigned ptrSize = gDataLayout->getPointerSize();
            // Add frame pointer types for all but last frame
            for (unsigned i = 0; i < (depth - 1); ++i)
                builder.addType(innerFrameType->getElementType(i), ptrSize);
            // Add frame pointer type for last frame
            builder.addType(LLPointerType::getUnqual(innerFrameType), ptrSize);
        }

        // Add the direct nested variables of this function, and update their indices to match.
        // TODO: optimize ordering for minimal space usage?
        for (auto vd : fd->closureVars)
        {
            unsigned alignment = DtoAlignment(vd);
            if (alignment > 1)
                builder.alignCurrentOffset(alignment);

            IrLocal& irLocal = *getIrLocal(vd, true);
            irLocal.nestedIndex = builder.currentFieldIndex();
            irLocal.nestedDepth = depth;

            LLType* t = NULL;
            if (vd->isParameter() && getIrParameter(vd)->arg)
            {
                // Parameters that are part of the LLVM signature will have
                // storage associated with them (to handle byref etc.), so
                // handle those cases specially by storing a pointer instead
                // of a value.
                const IrParameter* irparam = getIrParameter(vd);
                const bool refout = vd->storage_class & (STCref | STCout);
                const bool lazy = vd->storage_class & STClazy;
                const bool byref = irparam->arg->byref;
                const bool isVthisPtr = irparam->isVthis && !byref;
                if (!(refout || (byref && !lazy)) || isVthisPtr)
                {
                    // This will be copied to the nesting frame.
                    if (lazy)
                        t = irparam->value->getType()->getContainedType(0);
                    else
                        t = DtoMemType(vd->type);
                }
                else
                    t = irparam->value->getType();
            }
            else if (isSpecialRefVar(vd))
                t = DtoType(vd->type->pointerTo());
            else
                t = DtoMemType(vd->type);

            builder.addType(t, getTypeAllocSize(t));

            IF_LOG Logger::cout() << "Nested var '" << vd->toChars()
                                  << "' of type " << *t << "\n";
        }

        LLStructType* frameType = LLStructType::create(gIR->context(), builder.defaultTypes(),
                                                       std::string("nest.") + fd->toChars());

        IF_LOG Logger::cout() << "frameType = " << *frameType << '\n';

        // Store type in IrFunction
        irFunc.frameType = frameType;
        irFunc.frameTypeAlignment = builder.overallAlignment();
    }
    else // no captured variables
    {
        if (parentFunc)
        {
            // Propagate context arg properties if the context arg is passed on unmodified.
            IrFunction& parentIrFunc = *getIrFunc(parentFunc);
            irFunc.frameType = parentIrFunc.frameType;
            irFunc.frameTypeAlignment = parentIrFunc.frameTypeAlignment;
            irFunc.depth = parentIrFunc.depth;
        }
    }
}


void DtoCreateNestedContext(FuncDeclaration* fd) {
    IF_LOG Logger::println("DtoCreateNestedContext for %s", fd->toPrettyChars());
    LOG_SCOPE

    DtoCreateNestedContextType(fd);

    // construct nested variables array
    if (fd->closureVars.dim > 0)
    {
        IrFunction* irfunction = getIrFunc(fd);
        unsigned depth = irfunction->depth;
        LLStructType *frameType = irfunction->frameType;
        // Create frame for current function and append to frames list
        LLValue* frame = 0;
        bool needsClosure = fd->needsClosure();
        if (needsClosure)
        {
            // FIXME: alignment ?
            frame = DtoGcMalloc(fd->loc, frameType, ".frame");
        }
        else
        {
            unsigned alignment = std::max(getABITypeAlign(frameType), irfunction->frameTypeAlignment);
            frame = DtoRawAlloca(frameType, alignment, ".frame");
        }

        // copy parent frames into beginning
        if (depth != 0) {
            LLValue* src = irfunction->nestArg;
            if (!src) {
                assert(irfunction->thisArg);
                assert(fd->isMember2());
                LLValue* thisval = DtoLoad(irfunction->thisArg);
                AggregateDeclaration* cd = fd->isMember2();
                assert(cd);
                assert(cd->vthis);
                Logger::println("Indexing to 'this'");
                if (cd->isStructDeclaration())
                    src = DtoExtractValue(thisval, getVthisIdx(cd), ".vthis");
                else
                    src = DtoLoad(DtoGEPi(thisval, 0, getVthisIdx(cd), ".vthis"));
            } else {
                src = DtoLoad(src);
            }
            if (depth > 1) {
                src = DtoBitCast(src, getVoidPtrType());
                LLValue* dst = DtoBitCast(frame, getVoidPtrType());
                DtoMemCpy(dst, src, DtoConstSize_t((depth-1) * Target::ptrsize),
                    getABITypeAlign(getVoidPtrType()));
            }
            // Copy nestArg into framelist; the outer frame is not in the list of pointers
            src = DtoBitCast(src, frameType->getContainedType(depth-1));
            LLValue* gep = DtoGEPi(frame, 0, depth-1);
            DtoAlignedStore(src, gep);
        }

        // store context in IrFunction
        irfunction->nestedVar = frame;

        // go through all nested vars and assign addresses where possible.
        for (auto vd : fd->closureVars) {
            if (needsClosure && vd->needsAutoDtor()) {
                // This should really be a front-end, not a glue layer error,
                // but we need to fix this in DMD too.
                vd->error("has scoped destruction, cannot build closure");
            }

            IrLocal *irLocal = getIrLocal(vd);
            LLValue* gep = DtoGEPi(frame, 0, irLocal->nestedIndex, vd->toChars());
            if (vd->isParameter()) {
                IF_LOG Logger::println("nested param: %s", vd->toChars());
                LOG_SCOPE
                IrParameter* parm = getIrParameter(vd);

                if (parm->arg && parm->arg->byref)
                {
                    storeVariable(vd, gep);
                }
                else
                {
                    Logger::println("Copying to nested frame");
                    // The parameter value is an alloca'd stack slot.
                    // Copy to the nesting frame and leave the alloca for
                    // the optimizers to clean up.
                    DtoStore(DtoLoad(parm->value), gep);
                    gep->takeName(parm->value);
                    parm->value = gep;
                }
            } else {
                IF_LOG Logger::println("nested var:   %s", vd->toChars());
                assert(!irLocal->value);
                irLocal->value = gep;
            }

            if (global.params.symdebug) {
#if LDC_LLVM_VER >= 306
                LLSmallVector<int64_t, 2> addr;
#else
                LLSmallVector<LLValue*, 2> addr;
#endif
                gIR->DBuilder.OpOffset(addr, frameType, irLocal->nestedIndex);
                gIR->DBuilder.EmitLocalVariable(gep, vd, 0, false, addr);
            }
        }
    }
}