ldc/gen/functions.cpp

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

#include "gen/functions.h"
#include "aggregate.h"
#include "declaration.h"
#include "id.h"
#include "init.h"
#include "module.h"
#include "mtype.h"
#include "statement.h"
#include "template.h"
#include "gen/abi.h"
#include "gen/arrays.h"
#include "gen/classes.h"
#include "gen/dvalue.h"
#include "gen/irstate.h"
#include "gen/linkage.h"
#include "gen/llvm.h"
#include "gen/llvmhelpers.h"
#include "gen/logger.h"
#include "gen/nested.h"
#include "gen/optimizer.h"
#include "gen/pragma.h"
#include "gen/runtime.h"
#include "gen/tollvm.h"
#if LDC_LLVM_VER >= 305
#include "llvm/Linker/Linker.h"
#else
#include "llvm/Linker.h"
#endif
#if LDC_LLVM_VER >= 303
#include "llvm/IR/Intrinsics.h"
#else
#include "llvm/Intrinsics.h"
#endif
#if LDC_LLVM_VER >= 305
#include "llvm/IR/CFG.h"
#else
#include "llvm/Support/CFG.h"
#endif
#include <iostream>

llvm::FunctionType* DtoFunctionType(Type* type, IrFuncTy &irFty, Type* thistype, Type* nesttype,
                                    bool isMain, bool isCtor, bool isIntrinsic)
{
    IF_LOG Logger::println("DtoFunctionType(%s)", type->toChars());
    LOG_SCOPE

    // sanity check
    assert(type->ty == Tfunction);
    TypeFunction* f = static_cast<TypeFunction*>(type);
    assert(f->next && "Encountered function type with invalid return type; "
        "trying to codegen function ignored by the frontend?");

    // Return cached type if available
    if (irFty.funcType) return irFty.funcType;

    TargetABI* abi = (isIntrinsic ? TargetABI::getIntrinsic() : gABI);

    // Do not modify irFty yet; this function may be called recursively if any
    // of the argument types refer to this type.
    IrFuncTy newIrFty;

    // llvm idx counter
    size_t lidx = 0;

    // main needs a little special handling
    if (isMain)
    {
        newIrFty.ret = new IrFuncTyArg(Type::tint32, false);
    }
    // sane return value
    else
    {
        Type* rt = f->next;
        const bool byref = f->isref && rt->toBasetype()->ty != Tvoid;
        AttrBuilder attrBuilder;

        // sret return
        if (abi->returnInArg(f))
        {
            newIrFty.arg_sret = new IrFuncTyArg(rt, true,
                AttrBuilder().add(LDC_ATTRIBUTE(StructRet)).add(LDC_ATTRIBUTE(NoAlias)));
            rt = Type::tvoid;
            lidx++;
        }
        // sext/zext return
        else
        {
            attrBuilder.add(DtoShouldExtend(byref ? rt->pointerTo() : rt));
        }
        newIrFty.ret = new IrFuncTyArg(rt, byref, attrBuilder);
    }
    lidx++;

    // member functions
    if (thistype)
    {
        AttrBuilder attrBuilder;
#if LDC_LLVM_VER >= 303
        if (isCtor)
            attrBuilder.add(LDC_ATTRIBUTE(Returned));
#endif
        newIrFty.arg_this = new IrFuncTyArg(thistype, thistype->toBasetype()->ty == Tstruct, attrBuilder);
        lidx++;
    }

    // and nested functions
    else if (nesttype)
    {
        newIrFty.arg_nest = new IrFuncTyArg(nesttype, false);
        lidx++;
    }

    // vararg functions are special too
    if (f->varargs)
    {
        if (f->linkage == LINKd)
        {
            // d style with hidden args
            // 2 (array) is handled by the frontend
            if (f->varargs == 1)
            {
                // _arguments
                newIrFty.arg_arguments = new IrFuncTyArg(Type::dtypeinfo->type->arrayOf(), false);
                lidx++;
            }
        }

        newIrFty.c_vararg = true;
    }

    // if this _Dmain() doesn't have an argument, we force it to have one
    int nargs = Parameter::dim(f->parameters);

    if (isMain && nargs == 0)
    {
        Type* mainargs = Type::tchar->arrayOf()->arrayOf();
        newIrFty.args.push_back(new IrFuncTyArg(mainargs, false));
        lidx++;
    }
    // add explicit parameters
    else for (int i = 0; i < nargs; i++)
    {
        // get argument
        Parameter* arg = Parameter::getNth(f->parameters, i);

        // reference semantics? ref, out and d1 static arrays are
        bool byref = arg->storageClass & (STCref|STCout);

        Type* argtype = arg->type;
        AttrBuilder attrBuilder;

        // handle lazy args
        if (arg->storageClass & STClazy)
        {
            Logger::println("lazy param");
            TypeFunction *ltf = new TypeFunction(NULL, arg->type, 0, LINKd);
            TypeDelegate *ltd = new TypeDelegate(ltf);
            argtype = ltd;
        }
        else if (!byref)
        {
            // byval
            if (abi->passByVal(argtype))
            {
                attrBuilder.add(LDC_ATTRIBUTE(ByVal));
                // set byref, because byval requires a pointed LLVM type
                byref = true;
            }
            // sext/zext
            else
            {
                attrBuilder.add(DtoShouldExtend(argtype));
            }
        }
        newIrFty.args.push_back(new IrFuncTyArg(argtype, byref, attrBuilder));
        lidx++;
    }

    // let the abi rewrite the types as necesary
    abi->rewriteFunctionType(f, newIrFty);

    // Now we can modify irFty safely.
    irFty = llvm_move(newIrFty);

    // build the function type
    std::vector<LLType*> argtypes;
    argtypes.reserve(lidx);

    if (irFty.arg_sret) argtypes.push_back(irFty.arg_sret->ltype);
    if (irFty.arg_this) argtypes.push_back(irFty.arg_this->ltype);
    if (irFty.arg_nest) argtypes.push_back(irFty.arg_nest->ltype);
    if (irFty.arg_arguments) argtypes.push_back(irFty.arg_arguments->ltype);

    size_t beg = argtypes.size();
    size_t nargs2 = irFty.args.size();
    for (size_t i = 0; i < nargs2; i++)
    {
        argtypes.push_back(irFty.args[i]->ltype);
    }

    // reverse params?
    if (irFty.reverseParams && nargs2 > 1)
    {
        std::reverse(argtypes.begin() + beg, argtypes.end());
    }

    irFty.funcType = LLFunctionType::get(irFty.ret->ltype, argtypes, irFty.c_vararg);

    IF_LOG Logger::cout() << "Final function type: " << *irFty.funcType << "\n";

    return irFty.funcType;
}

//////////////////////////////////////////////////////////////////////////////////////////

#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/SourceMgr.h"
#if LDC_LLVM_VER >= 305
#include "llvm/AsmParser/Parser.h"
#else
#include "llvm/Assembly/Parser.h"
#endif

LLFunction* DtoInlineIRFunction(FuncDeclaration* fdecl)
{
    const char* mangled_name = mangleExact(fdecl);
    TemplateInstance* tinst = fdecl->parent->isTemplateInstance();
    assert(tinst);

    Objects& objs = tinst->tdtypes;
    assert(objs.dim == 3);

    Expression* a0 = isExpression(objs[0]);
    assert(a0);
    StringExp* strexp = a0->toStringExp();
    assert(strexp);
    assert(strexp->sz == 1);
    std::string code(static_cast<char*>(strexp->string), strexp->len);

    Type* ret = isType(objs[1]);
    assert(ret);

    Tuple* a2 = isTuple(objs[2]);
    assert(a2);
    Objects& arg_types = a2->objects;

    std::string str;
    llvm::raw_string_ostream stream(str);
    stream << "define " << *DtoType(ret) << " @" << mangled_name << "(";

    for(size_t i = 0; ;)
    {
        Type* ty = isType(arg_types[i]);
        //assert(ty);
        if(!ty)
        {
            error(tinst->loc,
                "All parameters of a template defined with pragma llvm_inline_ir, except for the first one, should be types");
            fatal();
        }
        stream << *DtoType(ty);

        i++;
        if(i >= arg_types.dim)
            break;

        stream << ", ";
    }

    if(ret->ty == Tvoid)
        code.append("\nret void");

    stream << ")\n{\n" << code <<  "\n}";

    llvm::SMDiagnostic err;

#if LDC_LLVM_VER >= 306
    std::unique_ptr<llvm::Module> m = llvm::parseAssemblyString(
        stream.str().c_str(), err, gIR->context());
#elif LDC_LLVM_VER >= 303
    llvm::Module* m = llvm::ParseAssemblyString(
        stream.str().c_str(), NULL, err, gIR->context());
#else
    llvm::ParseAssemblyString(
        stream.str().c_str(), gIR->module, err, gIR->context());
#endif

    std::string errstr = err.getMessage();
    if(errstr != "")
        error(tinst->loc,
            "can't parse inline LLVM IR:\n%s\n%s\n%s\nThe input string was: \n%s",
#if LDC_LLVM_VER >= 303
            err.getLineContents().str().c_str(),
#else
            err.getLineContents().c_str(),
#endif
            (std::string(err.getColumnNo(), ' ') + '^').c_str(),
            errstr.c_str(), stream.str().c_str());

#if LDC_LLVM_VER >= 306
    llvm::Linker(gIR->module).linkInModule(m.get());
#else
#if LDC_LLVM_VER >= 303
    std::string errstr2 = "";
#if LDC_LLVM_VER >= 306
    llvm::Linker(gIR->module).linkInModule(m.get(), &errstr2);
#else
    llvm::Linker(gIR->module).linkInModule(m, &errstr2);
#endif
    if(errstr2 != "")
        error(tinst->loc,
            "Error when linking in llvm inline ir: %s", errstr2.c_str());
#endif
#endif

    LLFunction* fun = gIR->module->getFunction(mangled_name);
    fun->setLinkage(llvm::GlobalValue::LinkOnceODRLinkage);
    fun->addFnAttr(LDC_ATTRIBUTE(AlwaysInline));
    return fun;
}

//////////////////////////////////////////////////////////////////////////////////////////

static llvm::FunctionType* DtoVaFunctionType(FuncDeclaration* fdecl)
{
    IrFuncTy &irFty = getIrFunc(fdecl, true)->irFty;
    if (irFty.funcType) return irFty.funcType;

    irFty.ret = new IrFuncTyArg(Type::tvoid, false);

    irFty.args.push_back(new IrFuncTyArg(Type::tvoid->pointerTo(), false));

    if (fdecl->llvmInternal == LLVMva_start)
        irFty.funcType = GET_INTRINSIC_DECL(vastart)->getFunctionType();
    else if (fdecl->llvmInternal == LLVMva_copy) {
        irFty.funcType = GET_INTRINSIC_DECL(vacopy)->getFunctionType();
        irFty.args.push_back(new IrFuncTyArg(Type::tvoid->pointerTo(), false));
    }
    else if (fdecl->llvmInternal == LLVMva_end)
        irFty.funcType = GET_INTRINSIC_DECL(vaend)->getFunctionType();
    assert(irFty.funcType);

    return irFty.funcType;
}

//////////////////////////////////////////////////////////////////////////////////////////

llvm::FunctionType* DtoFunctionType(FuncDeclaration* fdecl)
{
    // handle for C vararg intrinsics
    if (DtoIsVaIntrinsic(fdecl))
        return DtoVaFunctionType(fdecl);

    Type *dthis=0, *dnest=0;

    if (fdecl->ident == Id::ensure || fdecl->ident == Id::require) {
        FuncDeclaration *p = fdecl->parent->isFuncDeclaration();
        assert(p);
        AggregateDeclaration *ad = p->isMember2();
        assert(ad);
        dnest = Type::tvoid->pointerTo();
    } else
    if (fdecl->needThis()) {
        if (AggregateDeclaration* ad = fdecl->isMember2()) {
            IF_LOG Logger::println("isMember = this is: %s", ad->type->toChars());
            dthis = ad->type;
            LLType* thisty = DtoType(dthis);
            //Logger::cout() << "this llvm type: " << *thisty << '\n';
            if (ad->isStructDeclaration())
                thisty = getPtrToType(thisty);
        }
        else {
            IF_LOG Logger::println("chars: %s type: %s kind: %s", fdecl->toChars(), fdecl->type->toChars(), fdecl->kind());
            llvm_unreachable("needThis, but invalid parent declaration.");
        }
    }
    else if (fdecl->isNested()) {
        dnest = Type::tvoid->pointerTo();
    }

    LLFunctionType* functype = DtoFunctionType(fdecl->type, getIrFunc(fdecl, true)->irFty, dthis, dnest,
                                               fdecl->isMain(), fdecl->isCtorDeclaration(),
                                               fdecl->llvmInternal == LLVMintrinsic);

    return functype;
}

//////////////////////////////////////////////////////////////////////////////////////////

static llvm::Function* DtoDeclareVaFunction(FuncDeclaration* fdecl)
{
    DtoVaFunctionType(fdecl);
    llvm::Function* func = 0;

    if (fdecl->llvmInternal == LLVMva_start)
        func = GET_INTRINSIC_DECL(vastart);
    else if (fdecl->llvmInternal == LLVMva_copy)
        func = GET_INTRINSIC_DECL(vacopy);
    else if (fdecl->llvmInternal == LLVMva_end)
        func = GET_INTRINSIC_DECL(vaend);
    assert(func);

    getIrFunc(fdecl)->func = func;
    return func;
}

//////////////////////////////////////////////////////////////////////////////////////////

void DtoResolveFunction(FuncDeclaration* fdecl)
{
    if ((!global.params.useUnitTests || !fdecl->type) && fdecl->isUnitTestDeclaration()) {
        IF_LOG Logger::println("Ignoring unittest %s", fdecl->toPrettyChars());
        return; // ignore declaration completely
    }

    if (fdecl->ir.isResolved()) return;
    fdecl->ir.setResolved();

    Type *type = fdecl->type;
    // If errors occurred compiling it, such as bugzilla 6118
    if (type && type->ty == Tfunction) {
        Type *next = static_cast<TypeFunction *>(type)->next;
        if (!next || next->ty == Terror)
            return;
    }

    //printf("resolve function: %s\n", fdecl->toPrettyChars());

    if (fdecl->parent)
    if (TemplateInstance* tinst = fdecl->parent->isTemplateInstance())
    {
        if (TemplateDeclaration* tempdecl = tinst->tempdecl->isTemplateDeclaration())
        {
            if (tempdecl->llvmInternal == LLVMva_arg)
            {
                Logger::println("magic va_arg found");
                fdecl->llvmInternal = LLVMva_arg;
                fdecl->ir.setDefined();
                return; // this gets mapped to an instruction so a declaration makes no sence
            }
            else if (tempdecl->llvmInternal == LLVMva_start)
            {
                Logger::println("magic va_start found");
                fdecl->llvmInternal = LLVMva_start;
            }
            else if (tempdecl->llvmInternal == LLVMintrinsic)
            {
                Logger::println("overloaded intrinsic found");
                assert(fdecl->llvmInternal == LLVMintrinsic);
                assert(fdecl->mangleOverride);
            }
            else if (tempdecl->llvmInternal == LLVMinline_asm)
            {
                Logger::println("magic inline asm found");
                TypeFunction* tf = static_cast<TypeFunction*>(fdecl->type);
                if (tf->varargs != 1 || (fdecl->parameters && fdecl->parameters->dim != 0))
                {
                    tempdecl->error("invalid __asm declaration, must be a D style variadic with no explicit parameters");
                    fatal();
                }
                fdecl->llvmInternal = LLVMinline_asm;
                fdecl->ir.setDefined();
                return; // this gets mapped to a special inline asm call, no point in going on.
            }
            else if (tempdecl->llvmInternal == LLVMinline_ir)
            {
                Logger::println("magic inline ir found");
                fdecl->llvmInternal = LLVMinline_ir;
                fdecl->linkage = LINKc;
                Type* type = fdecl->type;
                assert(type->ty == Tfunction);
                static_cast<TypeFunction*>(type)->linkage = LINKc;

                DtoFunctionType(fdecl);
                DtoDeclareFunction(fdecl);
                fdecl->ir.setDefined();
                return;
            }
        }
    }

    DtoFunctionType(fdecl);

    IF_LOG Logger::println("DtoResolveFunction(%s): %s", fdecl->toPrettyChars(), fdecl->loc.toChars());
    LOG_SCOPE;

    // queue declaration unless the function is abstract without body
    if (!fdecl->isAbstract() || fdecl->fbody)
    {
        DtoDeclareFunction(fdecl);
    }
}

//////////////////////////////////////////////////////////////////////////////////////////

static void set_param_attrs(TypeFunction* f, llvm::Function* func, FuncDeclaration* fdecl)
{
    IrFuncTy &irFty = getIrFunc(fdecl)->irFty;
    AttrSet newAttrs = AttrSet::extractFunctionAndReturnAttributes(func);

    int idx = 0;

    // handle implicit args
    #define ADD_PA(X) \
    if (irFty.X) { \
        newAttrs.add(idx, irFty.X->attrs); \
        idx++; \
    }

    ADD_PA(ret)
    ADD_PA(arg_sret)
    ADD_PA(arg_this)
    ADD_PA(arg_nest)
    ADD_PA(arg_arguments)

    #undef ADD_PA

    // set attrs on the rest of the arguments
    size_t n = Parameter::dim(f->parameters);
    for (size_t k = 0; k < n; k++)
    {
        assert(Parameter::getNth(f->parameters, k));

        unsigned i = idx + (irFty.reverseParams ? n-k-1 : k);
        newAttrs.add(i, irFty.args[k]->attrs);
    }

    // Store the final attribute set
    func->setAttributes(newAttrs.toNativeSet());
}

//////////////////////////////////////////////////////////////////////////////////////////

void DtoDeclareFunction(FuncDeclaration* fdecl)
{
    DtoResolveFunction(fdecl);

    if (fdecl->ir.isDeclared()) return;
    fdecl->ir.setDeclared();

    IF_LOG Logger::println("DtoDeclareFunction(%s): %s", fdecl->toPrettyChars(), fdecl->loc.toChars());
    LOG_SCOPE;

    if (fdecl->isUnitTestDeclaration() && !global.params.useUnitTests)
    {
        Logger::println("unit tests not enabled");
        return;
    }

    //printf("declare function: %s\n", fdecl->toPrettyChars());

    // intrinsic sanity check
    if (fdecl->llvmInternal == LLVMintrinsic && fdecl->fbody) {
        error(fdecl->loc, "intrinsics cannot have function bodies");
        fatal();
    }

    // get TypeFunction*
    Type* t = fdecl->type->toBasetype();
    TypeFunction* f = static_cast<TypeFunction*>(t);

    // create IrFunction
    IrFunction *irFunc = getIrFunc(fdecl, true);

    LLFunction* vafunc = 0;
    if (DtoIsVaIntrinsic(fdecl))
        vafunc = DtoDeclareVaFunction(fdecl);

    // calling convention
    LINK link = f->linkage;
    if (vafunc || fdecl->llvmInternal == LLVMintrinsic
        // DMD treats _Dmain as having C calling convention and this has been
        // hardcoded into druntime, even if the frontend type has D linkage.
        // See Bugzilla issue 9028.
        || fdecl->isMain()
    )
    {
        link = LINKc;
    }

    // mangled name
    std::string mangledName(mangleExact(fdecl));
    mangledName = gABI->mangleForLLVM(mangledName, link);

    // construct function
    LLFunctionType* functype = DtoFunctionType(fdecl);
    LLFunction* func = vafunc ? vafunc : gIR->module->getFunction(mangledName);
    if (!func) {
        if(fdecl->llvmInternal == LLVMinline_ir)
        {
            func = DtoInlineIRFunction(fdecl);
        }
        else
        {
            // All function declarations are "external" - any other linkage type
            // is set when actually defining the function.
            func = LLFunction::Create(functype,
                llvm::GlobalValue::ExternalLinkage, mangledName, gIR->module);
        }
    } else if (func->getFunctionType() != functype) {
        error(fdecl->loc, "Function type does not match previously declared function with the same mangled name: %s", mangleExact(fdecl));
        fatal();
    }

    func->setCallingConv(gABI->callingConv(link));

    IF_LOG Logger::cout() << "func = " << *func << std::endl;

    // add func to IRFunc
    irFunc->func = func;

    // parameter attributes
    if (!DtoIsIntrinsic(fdecl)) {
        set_param_attrs(f, func, fdecl);
        if (global.params.disableRedZone) {
            func->addFnAttr(LDC_ATTRIBUTE(NoRedZone));
        }
    }

    // main
    if (fdecl->isMain()) {
        // Detect multiple main functions, which is disallowed. DMD checks this
        // in the glue code, so we need to do it here as well.
        if (gIR->mainFunc) {
            error(fdecl->loc, "only one main function allowed");
        }
        gIR->mainFunc = func;
    }

    if (fdecl->neverInline)
    {
        irFunc->setNeverInline();
    }

    if (fdecl->llvmInternal == LLVMglobal_crt_ctor || fdecl->llvmInternal == LLVMglobal_crt_dtor)
    {
        AppendFunctionToLLVMGlobalCtorsDtors(func, fdecl->priority, fdecl->llvmInternal == LLVMglobal_crt_ctor);
    }

    IrFuncTy &irFty = irFunc->irFty;

    // if (!declareOnly)
    {
        // name parameters
        llvm::Function::arg_iterator iarg = func->arg_begin();

        if (irFty.arg_sret) {
            iarg->setName(".sret_arg");
            irFunc->retArg = iarg;
            ++iarg;
        }

        if (irFty.arg_this) {
            iarg->setName(".this_arg");
            irFunc->thisArg = iarg;

            VarDeclaration* v = fdecl->vthis;
            if (v) {
                // We already build the this argument here if we will need it
                // later for codegen'ing the function, just as normal
                // parameters below, because it can be referred to in nested
                // context types. Will be given storage in DtoDefineFunction.
                assert(!isIrParameterCreated(v));
                IrParameter *irParam = getIrParameter(v, true);
                irParam->value = iarg;
                irParam->arg = irFty.arg_this;
                irParam->isVthis = true;
            }

            ++iarg;
        }
        else if (irFty.arg_nest) {
            iarg->setName(".nest_arg");
            irFunc->nestArg = iarg;
            assert(irFunc->nestArg);
            ++iarg;
        }

        if (irFty.arg_arguments) {
            iarg->setName("._arguments");
            irFunc->_arguments = iarg;
            ++iarg;
        }

        // we never reference parameters of function prototypes
        unsigned int k = 0;
        for (; iarg != func->arg_end(); ++iarg)
        {
            if (fdecl->parameters && fdecl->parameters->dim > k)
            {
                int paramIndex = irFty.reverseParams ? fdecl->parameters->dim-k-1 : k;
                Dsymbol* argsym = static_cast<Dsymbol*>(fdecl->parameters->data[paramIndex]);

                VarDeclaration* argvd = argsym->isVarDeclaration();
                assert(argvd);
                assert(!isIrLocalCreated(argvd));
                std::string str(argvd->ident->toChars());
                str.append("_arg");
                iarg->setName(str);

                IrParameter *irParam = getIrParameter(argvd, true);
                irParam->value = iarg;
                irParam->arg = irFty.args[paramIndex];

                k++;
            }
            else
            {
                iarg->setName("unnamed");
            }
        }
    }
}

//////////////////////////////////////////////////////////////////////////////////////////

static llvm::GlobalValue::LinkageTypes lowerFuncLinkage(FuncDeclaration* fdecl)
{
    // Intrinsics are always external.
    if (fdecl->llvmInternal == LLVMintrinsic)
        return llvm::GlobalValue::ExternalLinkage;

    // Generated array op functions behave like templates in that they might be
    // emitted into many different modules.
    if (fdecl->isArrayOp && (willInline() || !isDruntimeArrayOp(fdecl)))
        return templateLinkage;

    // A body-less declaration always needs to be marked as external in LLVM
    // (also e.g. naked template functions which would otherwise be weak_odr,
    // but where the definition is in module-level inline asm).
    if (!fdecl->fbody || fdecl->naked)
        return llvm::GlobalValue::ExternalLinkage;

    return DtoLinkage(fdecl);
}

void DtoDefineFunction(FuncDeclaration* fd)
{
    IF_LOG Logger::println("DtoDefineFunction(%s): %s", fd->toPrettyChars(), fd->loc.toChars());
    LOG_SCOPE;

    if (fd->ir.isDefined()) return;

    if ((fd->type && fd->type->ty == Terror) ||
        (fd->type && fd->type->ty == Tfunction && static_cast<TypeFunction *>(fd->type)->next == NULL) ||
        (fd->type && fd->type->ty == Tfunction && static_cast<TypeFunction *>(fd->type)->next->ty == Terror))
    {
        IF_LOG Logger::println("Ignoring; has error type, no return type or returns error type");
        fd->ir.setDefined();
        return;
    }

    if (fd->semanticRun == PASSsemanticdone)
    {
        /* What happened is this function failed semantic3() with errors,
         * but the errors were gagged.
         * Try to reproduce those errors, and then fail.
         */
        error(fd->loc, "errors compiling function %s", fd->toPrettyChars());
        fd->ir.setDefined();
        return;
    }

    DtoResolveFunction(fd);

    if (fd->isUnitTestDeclaration() && !global.params.useUnitTests)
    {
        IF_LOG Logger::println("No code generation for unit test declaration %s", fd->toChars());
        fd->ir.setDefined();
        return;
    }

    // Skip array ops implemented in druntime
    if (fd->isArrayOp && !willInline() && isDruntimeArrayOp(fd))
    {
        IF_LOG Logger::println("No code generation for array op %s implemented in druntime", fd->toChars());
        fd->ir.setDefined();
        return;
    }

    // Check whether the frontend knows that the function is already defined
    // in some other module (see DMD's FuncDeclaration::toObjFile).
    for (FuncDeclaration *f = fd; f; )
    {
        if (!f->isInstantiated() && f->inNonRoot())
        {
            IF_LOG Logger::println("Skipping '%s'.", fd->toPrettyChars());
            // TODO: Emit as available_externally for inlining purposes instead
            // (see #673).
            fd->ir.setDefined();
            return;
        }
        if (f->isNested())
            f = f->toParent2()->isFuncDeclaration();
        else
            break;
    }

    DtoDeclareFunction(fd);
    assert(fd->ir.isDeclared());

    // DtoResolveFunction might also set the defined flag for functions we
    // should not touch.
    if (fd->ir.isDefined()) return;
    fd->ir.setDefined();

    // We cannot emit nested functions with parents that have not gone through
    // semantic analysis. This can happen as DMD leaks some template instances
    // from constraints into the module member list. DMD gets away with being
    // sloppy as functions in template contraints obviously never need to access
    // data from the template function itself, but it would still mess up our
    // nested context creation code.
    FuncDeclaration* parent = fd;
    while ((parent = getParentFunc(parent, true)))
    {
        if (parent->semanticRun != PASSsemantic3done || parent->semantic3Errors)
        {
            IF_LOG Logger::println("Ignoring nested function with unanalyzed parent.");
            return;
        }
    }

    assert(fd->semanticRun == PASSsemantic3done);
    assert(fd->ident != Id::empty);

    if (fd->isUnitTestDeclaration()) {
        gIR->unitTests.push_back(fd);
    } else if (fd->isSharedStaticCtorDeclaration()) {
        gIR->sharedCtors.push_back(fd);
    } else if (StaticDtorDeclaration *dtorDecl = fd->isSharedStaticDtorDeclaration()) {
        gIR->sharedDtors.push_front(fd);
        if (dtorDecl->vgate)
            gIR->sharedGates.push_front(dtorDecl->vgate);
    } else if (fd->isStaticCtorDeclaration()) {
        gIR->ctors.push_back(fd);
    } else if (StaticDtorDeclaration *dtorDecl = fd->isStaticDtorDeclaration()) {
        gIR->dtors.push_front(fd);
        if (dtorDecl->vgate)
            gIR->gates.push_front(dtorDecl->vgate);
    }


    // if this function is naked, we take over right away! no standard processing!
    if (fd->naked)
    {
        DtoDefineNakedFunction(fd);
        return;
    }

    IrFunction *irFunc = getIrFunc(fd);
    IrFuncTy &irFty = irFunc->irFty;

    // debug info
    irFunc->diSubprogram = gIR->DBuilder.EmitSubProgram(fd);

    Type* t = fd->type->toBasetype();
    TypeFunction* f = static_cast<TypeFunction*>(t);
    // assert(f->ctype);

    llvm::Function* func = irFunc->func;

    // is there a body?
    if (fd->fbody == NULL)
        return;

    IF_LOG Logger::println("Doing function body for: %s", fd->toChars());
    gIR->functions.push_back(irFunc);

    if (fd->isMain())
        gIR->emitMain = true;

    func->setLinkage(lowerFuncLinkage(fd));

    // On x86_64, always set 'uwtable' for System V ABI compatibility.
    // TODO: Find a better place for this.
    // TODO: Is this required for Win64 as well?
    if (global.params.targetTriple.getArch() == llvm::Triple::x86_64)
    {
        func->addFnAttr(LDC_ATTRIBUTE(UWTable));
    }
#if LDC_LLVM_VER >= 303
    if (opts::sanitize != opts::None) {
        // Set the required sanitizer attribute.
        if (opts::sanitize == opts::AddressSanitizer) {
            func->addFnAttr(LDC_ATTRIBUTE(SanitizeAddress));
        }

        if (opts::sanitize == opts::MemorySanitizer) {
            func->addFnAttr(LDC_ATTRIBUTE(SanitizeMemory));
        }

        if (opts::sanitize == opts::ThreadSanitizer) {
            func->addFnAttr(LDC_ATTRIBUTE(SanitizeThread));
        }
    }
#endif

    llvm::BasicBlock* beginbb = llvm::BasicBlock::Create(gIR->context(), "", func);
    llvm::BasicBlock* endbb = llvm::BasicBlock::Create(gIR->context(), "endentry", func);

    //assert(gIR->scopes.empty());
    gIR->scopes.push_back(IRScope(beginbb, endbb));

    // create alloca point
    // this gets erased when the function is complete, so alignment etc does not matter at all
    llvm::Instruction* allocaPoint = new llvm::AllocaInst(LLType::getInt32Ty(gIR->context()), "alloca point", beginbb);
    irFunc->allocapoint = allocaPoint;

    // debug info - after all allocas, but before any llvm.dbg.declare etc
    gIR->DBuilder.EmitFuncStart(fd);

    // this hack makes sure the frame pointer elimination optimization is disabled.
    // this this eliminates a bunch of inline asm related issues.
    if (fd->hasReturnExp & 8) // has inline asm
    {
        // emit a call to llvm_eh_unwind_init
        LLFunction* hack = GET_INTRINSIC_DECL(eh_unwind_init);
#if LDC_LLVM_VER >= 307
        gIR->ir->CreateCall(hack, {});
#else
        gIR->ir->CreateCall(hack, "");
#endif
    }

    // give the 'this' argument storage and debug info
    if (irFty.arg_this)
    {
        LLValue* thisvar = irFunc->thisArg;
        assert(thisvar);

        LLValue* thismem = thisvar;
        if (!irFty.arg_this->byref)
        {
            thismem = DtoRawAlloca(thisvar->getType(), 0, "this"); // FIXME: align?
            DtoStore(thisvar, thismem);
            irFunc->thisArg = thismem;
        }

        assert(getIrParameter(fd->vthis)->value == thisvar);
        getIrParameter(fd->vthis)->value = thismem;

        gIR->DBuilder.EmitLocalVariable(thismem, fd->vthis);
    }

    // give the 'nestArg' storage
    if (irFty.arg_nest)
    {
        LLValue *nestArg = irFunc->nestArg;
        LLValue *val = DtoRawAlloca(nestArg->getType(), 0, "nestedFrame");
        DtoStore(nestArg, val);
        irFunc->nestArg = val;
    }

    // give arguments storage
    // and debug info
    if (fd->parameters)
    {
        size_t n = irFty.args.size();
        assert(n == fd->parameters->dim);
        for (size_t i=0; i < n; ++i)
        {
            Dsymbol* argsym = static_cast<Dsymbol*>(fd->parameters->data[i]);
            VarDeclaration* vd = argsym->isVarDeclaration();
            assert(vd);

            IrParameter* irparam = getIrParameter(vd);
            assert(irparam);

            bool refout = vd->storage_class & (STCref | STCout);
            bool lazy = vd->storage_class & STClazy;
            if (!refout && (!irparam->arg->byref || lazy))
            {
                // alloca a stack slot for this first class value arg
                LLValue* mem = DtoAlloca(irparam->arg->type, vd->ident->toChars());

                // let the abi transform the argument back first
                DImValue arg_dval(vd->type, irparam->value);
                irFty.getParam(vd->type, i, &arg_dval, mem);

                // set the arg var value to the alloca
                irparam->value = mem;
            }

            if (global.params.symdebug && !(isaArgument(irparam->value) && isaArgument(irparam->value)->hasByValAttr()) && !refout)
                gIR->DBuilder.EmitLocalVariable(irparam->value, vd);
        }
    }

    FuncGen fg;
    irFunc->gen = &fg;

    DtoCreateNestedContext(fd);

    if (fd->vresult && !
        fd->vresult->nestedrefs.dim // FIXME: not sure here :/
    )
    {
        DtoVarDeclaration(fd->vresult);
    }

    // D varargs: prepare _argptr and _arguments
    if (f->linkage == LINKd && f->varargs == 1)
    {
        // allocate _argptr (of type core.stdc.stdarg.va_list)
        LLValue* argptrmem = DtoAlloca(Type::tvalist, "_argptr_mem");
        irFunc->_argptr = argptrmem;

        // initialize _argptr with a call to the va_start intrinsic
        LLValue* vaStartArg = gABI->prepareVaStart(argptrmem);
        llvm::CallInst::Create(GET_INTRINSIC_DECL(vastart), vaStartArg, "", gIR->scopebb());

        // copy _arguments to a memory location
        LLType* argumentsType = irFunc->_arguments->getType();
        LLValue* argumentsmem = DtoRawAlloca(argumentsType, 0, "_arguments_mem");
        new llvm::StoreInst(irFunc->_arguments, argumentsmem, gIR->scopebb());
        irFunc->_arguments = argumentsmem;
    }

    // output function body
    codegenFunction(fd->fbody, gIR);
    irFunc->gen = 0;

    llvm::BasicBlock* bb = gIR->scopebb();
    if (pred_begin(bb) == pred_end(bb) && bb != &bb->getParent()->getEntryBlock()) {
        // This block is trivially unreachable, so just delete it.
        // (This is a common case because it happens when 'return'
        // is the last statement in a function)
        bb->eraseFromParent();
    } else if (!gIR->scopereturned()) {
        // llvm requires all basic blocks to end with a TerminatorInst but DMD does not put a return statement
        // in automatically, so we do it here.

        // pass the previous block into this block
        gIR->DBuilder.EmitFuncEnd(fd);
        if (func->getReturnType() == LLType::getVoidTy(gIR->context())) {
            llvm::ReturnInst::Create(gIR->context(), gIR->scopebb());
        }
        else if (!fd->isMain()) {
            CompoundAsmStatement* asmb = fd->fbody->endsWithAsm();
            if (asmb) {
                assert(asmb->abiret);
                llvm::ReturnInst::Create(gIR->context(), asmb->abiret, bb);
            }
            else {
                llvm::ReturnInst::Create(gIR->context(), llvm::UndefValue::get(func->getReturnType()), bb);
            }
        }
        else
            llvm::ReturnInst::Create(gIR->context(), LLConstant::getNullValue(func->getReturnType()), bb);
    }

    // erase alloca point
    if (allocaPoint->getParent())
        allocaPoint->eraseFromParent();
    allocaPoint = 0;
    gIR->func()->allocapoint = 0;

    gIR->scopes.pop_back();

    // get rid of the endentry block, it's never used
    assert(!func->getBasicBlockList().empty());
    func->getBasicBlockList().pop_back();

    gIR->functions.pop_back();
}

//////////////////////////////////////////////////////////////////////////////////////////

DValue* DtoArgument(Parameter* fnarg, Expression* argexp)
{
    IF_LOG Logger::println("DtoArgument");
    LOG_SCOPE;

    // ref/out arg
    if (fnarg && (fnarg->storageClass & (STCref | STCout)))
    {
        Loc loc;
        DValue* arg = toElem(argexp, true);
        return new DImValue(argexp->type, arg->isLVal() ? arg->getLVal() : makeLValue(loc, arg));
    }

    DValue* arg = toElem(argexp);

    // lazy arg
    if (fnarg && (fnarg->storageClass & STClazy))
    {
        assert(argexp->type->toBasetype()->ty == Tdelegate);
        assert(!arg->isLVal());
        return arg;
    }

    // byval arg, but expr has no storage yet
    if (DtoIsPassedByRef(argexp->type) && (arg->isSlice() || arg->isNull()))
    {
        LLValue* alloc = DtoAlloca(argexp->type, ".tmp_arg");
        DVarValue* vv = new DVarValue(argexp->type, alloc);
        DtoAssign(argexp->loc, vv, arg);
        arg = vv;
    }

    return arg;
}

//////////////////////////////////////////////////////////////////////////////////////////

int binary(const char *p , const char **tab, int high)
{
    int i = 0, j = high, k, l;
    do
    {
        k = (i + j) / 2;
        l = strcmp(p, tab[k]);
        if (!l)
            return k;
        else if (l < 0)
            j = k;
        else
            i = k + 1;
    }
    while (i != j);
    return -1;
}

int isDruntimeArrayOp(FuncDeclaration *fd)
{
    /* Some of the array op functions are written as library functions,
     * presumably to optimize them with special CPU vector instructions.
     * List those library functions here, in alpha order.
     */
    static const char *libArrayopFuncs[] =
    {
        "_arrayExpSliceAddass_a",
        "_arrayExpSliceAddass_d",
        "_arrayExpSliceAddass_f",           // T[]+=T
        "_arrayExpSliceAddass_g",
        "_arrayExpSliceAddass_h",
        "_arrayExpSliceAddass_i",
        "_arrayExpSliceAddass_k",
        "_arrayExpSliceAddass_s",
        "_arrayExpSliceAddass_t",
        "_arrayExpSliceAddass_u",
        "_arrayExpSliceAddass_w",

        "_arrayExpSliceDivass_d",           // T[]/=T
        "_arrayExpSliceDivass_f",           // T[]/=T

        "_arrayExpSliceMinSliceAssign_a",
        "_arrayExpSliceMinSliceAssign_d",   // T[]=T-T[]
        "_arrayExpSliceMinSliceAssign_f",   // T[]=T-T[]
        "_arrayExpSliceMinSliceAssign_g",
        "_arrayExpSliceMinSliceAssign_h",
        "_arrayExpSliceMinSliceAssign_i",
        "_arrayExpSliceMinSliceAssign_k",
        "_arrayExpSliceMinSliceAssign_s",
        "_arrayExpSliceMinSliceAssign_t",
        "_arrayExpSliceMinSliceAssign_u",
        "_arrayExpSliceMinSliceAssign_w",

        "_arrayExpSliceMinass_a",
        "_arrayExpSliceMinass_d",           // T[]-=T
        "_arrayExpSliceMinass_f",           // T[]-=T
        "_arrayExpSliceMinass_g",
        "_arrayExpSliceMinass_h",
        "_arrayExpSliceMinass_i",
        "_arrayExpSliceMinass_k",
        "_arrayExpSliceMinass_s",
        "_arrayExpSliceMinass_t",
        "_arrayExpSliceMinass_u",
        "_arrayExpSliceMinass_w",

        "_arrayExpSliceMulass_d",           // T[]*=T
        "_arrayExpSliceMulass_f",           // T[]*=T
        "_arrayExpSliceMulass_i",
        "_arrayExpSliceMulass_k",
        "_arrayExpSliceMulass_s",
        "_arrayExpSliceMulass_t",
        "_arrayExpSliceMulass_u",
        "_arrayExpSliceMulass_w",

        "_arraySliceExpAddSliceAssign_a",
        "_arraySliceExpAddSliceAssign_d",   // T[]=T[]+T
        "_arraySliceExpAddSliceAssign_f",   // T[]=T[]+T
        "_arraySliceExpAddSliceAssign_g",
        "_arraySliceExpAddSliceAssign_h",
        "_arraySliceExpAddSliceAssign_i",
        "_arraySliceExpAddSliceAssign_k",
        "_arraySliceExpAddSliceAssign_s",
        "_arraySliceExpAddSliceAssign_t",
        "_arraySliceExpAddSliceAssign_u",
        "_arraySliceExpAddSliceAssign_w",

        "_arraySliceExpDivSliceAssign_d",   // T[]=T[]/T
        "_arraySliceExpDivSliceAssign_f",   // T[]=T[]/T

        "_arraySliceExpMinSliceAssign_a",
        "_arraySliceExpMinSliceAssign_d",   // T[]=T[]-T
        "_arraySliceExpMinSliceAssign_f",   // T[]=T[]-T
        "_arraySliceExpMinSliceAssign_g",
        "_arraySliceExpMinSliceAssign_h",
        "_arraySliceExpMinSliceAssign_i",
        "_arraySliceExpMinSliceAssign_k",
        "_arraySliceExpMinSliceAssign_s",
        "_arraySliceExpMinSliceAssign_t",
        "_arraySliceExpMinSliceAssign_u",
        "_arraySliceExpMinSliceAssign_w",

        "_arraySliceExpMulSliceAddass_d",   // T[] += T[]*T
        "_arraySliceExpMulSliceAddass_f",
        "_arraySliceExpMulSliceAddass_r",

        "_arraySliceExpMulSliceAssign_d",   // T[]=T[]*T
        "_arraySliceExpMulSliceAssign_f",   // T[]=T[]*T
        "_arraySliceExpMulSliceAssign_i",
        "_arraySliceExpMulSliceAssign_k",
        "_arraySliceExpMulSliceAssign_s",
        "_arraySliceExpMulSliceAssign_t",
        "_arraySliceExpMulSliceAssign_u",
        "_arraySliceExpMulSliceAssign_w",

        "_arraySliceExpMulSliceMinass_d",   // T[] -= T[]*T
        "_arraySliceExpMulSliceMinass_f",
        "_arraySliceExpMulSliceMinass_r",

        "_arraySliceSliceAddSliceAssign_a",
        "_arraySliceSliceAddSliceAssign_d", // T[]=T[]+T[]
        "_arraySliceSliceAddSliceAssign_f", // T[]=T[]+T[]
        "_arraySliceSliceAddSliceAssign_g",
        "_arraySliceSliceAddSliceAssign_h",
        "_arraySliceSliceAddSliceAssign_i",
        "_arraySliceSliceAddSliceAssign_k",
        "_arraySliceSliceAddSliceAssign_r", // T[]=T[]+T[]
        "_arraySliceSliceAddSliceAssign_s",
        "_arraySliceSliceAddSliceAssign_t",
        "_arraySliceSliceAddSliceAssign_u",
        "_arraySliceSliceAddSliceAssign_w",

        "_arraySliceSliceAddass_a",
        "_arraySliceSliceAddass_d",         // T[]+=T[]
        "_arraySliceSliceAddass_f",         // T[]+=T[]
        "_arraySliceSliceAddass_g",
        "_arraySliceSliceAddass_h",
        "_arraySliceSliceAddass_i",
        "_arraySliceSliceAddass_k",
        "_arraySliceSliceAddass_s",
        "_arraySliceSliceAddass_t",
        "_arraySliceSliceAddass_u",
        "_arraySliceSliceAddass_w",

        "_arraySliceSliceMinSliceAssign_a",
        "_arraySliceSliceMinSliceAssign_d", // T[]=T[]-T[]
        "_arraySliceSliceMinSliceAssign_f", // T[]=T[]-T[]
        "_arraySliceSliceMinSliceAssign_g",
        "_arraySliceSliceMinSliceAssign_h",
        "_arraySliceSliceMinSliceAssign_i",
        "_arraySliceSliceMinSliceAssign_k",
        "_arraySliceSliceMinSliceAssign_r", // T[]=T[]-T[]
        "_arraySliceSliceMinSliceAssign_s",
        "_arraySliceSliceMinSliceAssign_t",
        "_arraySliceSliceMinSliceAssign_u",
        "_arraySliceSliceMinSliceAssign_w",

        "_arraySliceSliceMinass_a",
        "_arraySliceSliceMinass_d",         // T[]-=T[]
        "_arraySliceSliceMinass_f",         // T[]-=T[]
        "_arraySliceSliceMinass_g",
        "_arraySliceSliceMinass_h",
        "_arraySliceSliceMinass_i",
        "_arraySliceSliceMinass_k",
        "_arraySliceSliceMinass_s",
        "_arraySliceSliceMinass_t",
        "_arraySliceSliceMinass_u",
        "_arraySliceSliceMinass_w",

        "_arraySliceSliceMulSliceAssign_d", // T[]=T[]*T[]
        "_arraySliceSliceMulSliceAssign_f", // T[]=T[]*T[]
        "_arraySliceSliceMulSliceAssign_i",
        "_arraySliceSliceMulSliceAssign_k",
        "_arraySliceSliceMulSliceAssign_s",
        "_arraySliceSliceMulSliceAssign_t",
        "_arraySliceSliceMulSliceAssign_u",
        "_arraySliceSliceMulSliceAssign_w",

        "_arraySliceSliceMulass_d",         // T[]*=T[]
        "_arraySliceSliceMulass_f",         // T[]*=T[]
        "_arraySliceSliceMulass_i",
        "_arraySliceSliceMulass_k",
        "_arraySliceSliceMulass_s",
        "_arraySliceSliceMulass_t",
        "_arraySliceSliceMulass_u",
        "_arraySliceSliceMulass_w",
    };
    char *name = fd->ident->toChars();
    int i = binary(name, libArrayopFuncs, sizeof(libArrayopFuncs) / sizeof(char *));
    if (i != -1)
        return 1;

#ifdef DEBUG    // Make sure our array is alphabetized
    for (i = 0; i < sizeof(libArrayopFuncs) / sizeof(char *); i++)
    {
        if (strcmp(name, libArrayopFuncs[i]) == 0)
            assert(0);
    }
#endif
    return 0;
}