path: root/compiler_and_linker/unsorted/Alias.c

#include "compiler/Alias.h"
#include "compiler/CClass.h"
#include "compiler/CError.h"
#include "compiler/CParser.h"
#include "compiler/CMachine.h"
#include "compiler/CodeGen.h"
#include "compiler/CopyPropagation.h"
#include "compiler/PCode.h"
#include "compiler/PCodeInfo.h"
#include "compiler/RegisterInfo.h"
#include "compiler/UseDefChains.h"
#include "compiler/ValueNumbering.h"
#include "compiler/BitVectors.h"
#include "compiler/CompilerTools.h"
#include "compiler/objects.h"
#include "compiler/types.h"

static Alias *aliases;
static int n_aliases;
static int n_gathered_aliases;
static Alias *alias_hash[997];
Alias *worst_case;
Object worst_case_obj;

static TypePointer worst_case_memory_type = {
    TYPEARRAY,
    0xFFFFFF,
    TYPE(&stchar)
};

static Boolean is_safe_const(Object *obj) {
    Type *type;

    type = obj->type;
    while (IS_TYPE_ARRAY(type))
        type = TPTR_TARGET(type);

    if (TYPE_FITS_IN_REGISTER(type) || IS_TYPE_VECTOR(type) || IS_TYPE_FLOAT(type) || IS_TYPE_STRUCT(type))
        return is_const_object(obj);

    if (IS_TYPE_CLASS(type))
        return is_const_object(obj) && CClass_IsPODClass(TYPE_CLASS(type));

    return 0;
}

void initialize_aliases(void) {
    int i;

    memclrw(&worst_case_obj, sizeof(Object));
    worst_case_obj.otype = OT_OBJECT;
    worst_case_obj.type = TYPE(&worst_case_memory_type);
    worst_case_obj.datatype = DDATA;
    worst_case_obj.name = GetHashNameNodeExport("@worst_case@");

    aliases = NULL;
    n_aliases = 0;
    n_gathered_aliases = 0;
    for (i = 0; i < 997; i++)
        alias_hash[i] = NULL;

    worst_case = make_alias_set();
    add_alias_member(worst_case, make_alias(&worst_case_obj, 0, 0));
}

static UInt32 hash_alias(Object *object, SInt32 offset, SInt32 size) {
    return (UInt32) (object->name->hashval * offset * size) % 997;
}

static Alias *create_alias(AliasType type, Object *object, SInt32 offset, SInt32 size, Boolean addToHash) {
    Alias *alias;
    UInt32 hash;

    alias = lalloc(sizeof(Alias));
    memclrw(alias, sizeof(Alias));
    alias->type = type;
    alias->index = n_aliases++;
    alias->next = aliases;
    aliases = alias;
    alias->object = object;
    alias->offset = offset;
    alias->size = size;

    if (addToHash) {
        hash = hash_alias(object, offset, size);
        alias->hashNext = alias_hash[hash];
        alias_hash[hash] = alias;
    }

    return alias;
}

static Alias *lookup_alias(Object *object, SInt32 offset, SInt32 size) {
    Alias *scan;

    for (scan = alias_hash[hash_alias(object, offset, size)]; scan; scan = scan->hashNext) {
        if (scan->object == object && scan->offset == offset && scan->size == size)
            return scan;
    }

    return NULL;
}

Alias *make_alias(Object *object, SInt32 offset, SInt32 size) {
    Alias *alias;
    Alias *alias2;

    if (!offset && !size)
        size = object->type->size;

    alias = lookup_alias(object, offset, size);
    if (!alias) {
        if (offset > 0 || size != object->type->size) {
            alias2 = make_alias(object, 0, object->type->size);
            alias = create_alias(AliasType1, object, offset, size, 1);
            add_alias_member(alias2, alias);
        } else {
            alias = create_alias(AliasType0, object, offset, size, 1);
        }

        switch (object->datatype) {
            case DLOCAL:
            case DNONLAZYPTR:
                break;
            default:
                if (!is_safe_const(object))
                    add_alias_member(worst_case, make_alias(object, 0, 0));
        }
    }

    if (offset > object->type->size)
        return NULL;
    else
        return alias;
}

Alias *make_alias_set(void) {
    return create_alias(AliasType2, NULL, 0, 0, 0);
}

void add_alias_member(Alias *parent, Alias *child) {
    AliasMember *member;

    if (child->type == AliasType2) {
        for (member = child->parents; member; member = member->nextParent)
            add_alias_member(parent, member->child);
    } else {
        if (parent == worst_case && child->type == AliasType1)
            child = make_alias(child->object, 0, 0);

        for (member = parent->parents; member; member = member->nextParent) {
            if (member->child == child)
                return;
        }

        member = lalloc(sizeof(AliasMember));
        member->parent = parent;
        member->child = child;
        member->nextParent = parent->parents;
        parent->parents = member;
        member->nextChild = child->children;
        child->children = member;
    }
}

Alias *make_alias_set_from_IR(void) {
    CError_FATAL(333);
    return NULL;
}

static Boolean aliases_overlap(Alias *a, Alias *b) {
    return (
        a->offset == b->offset ||
        (a->offset > b->offset && a->offset < (b->offset + b->size)) ||
        (b->offset > a->offset && b->offset < (a->offset + a->size))
        );
}

static int is_address_load(PCode *pcode) {
    Object *obj;

    switch (pcode->op) {
        case PC_LWZ:
            if (pcode->args[2].kind == PCOp_MEMORY && pcode->args[2].data.mem.obj->datatype == DNONLAZYPTR)
                return 1;
            break;
        case PC_LBZU:
        case PC_LBZUX:
        case PC_LHZU:
        case PC_LHZUX:
        case PC_LHAU:
        case PC_LHAUX:
        case PC_LWZU:
        case PC_LWZUX:
        case PC_STBU:
        case PC_STBUX:
        case PC_STHU:
        case PC_STHUX:
        case PC_STWU:
        case PC_STWUX:
            return 1;
        case PC_ADDI:
        case PC_ADDIS:
            if (pcode->args[0].data.reg.reg < n_real_registers[RegClass_GPR]) {
                if (pcode->args[2].kind == PCOp_MEMORY) {
                    obj = pcode->args[2].data.mem.obj;
                    if (obj->datatype == DLOCAL && !is_safe_const(obj))
                        add_alias_member(worst_case, make_alias(obj, 0, 0));
                    return 0;
                }
            } else {
                return 1;
            }
            break;
        case PC_ADD:
            return 1;
    }

    return 0;
}

static int addresspropagatestouse(int candidateID, int useID) {
    PCode *candidate_pcode; // r30
    PCode *use_pcode; // r29
    int reg; // r28
    short reg2;
    Object *object; // r27
    SInt32 offset; // r26
    Alias *alias; // r25
    Boolean flag24; // r24
    SInt32 size; // r23
    Alias *aliasSet; // r22
    int i;
    PCode *scan;
    PCodeArg *op;

    candidate_pcode = Candidates[candidateID].pcode;
    use_pcode = Uses[useID].pcode;
    flag24 = 0;
    size = 1;
    reg = candidate_pcode->args[0].data.reg.reg;

    if (candidate_pcode->alias && (candidate_pcode->alias->type == AliasType0 || candidate_pcode->alias->type == AliasType1)) {
        object = candidate_pcode->alias->object;
        offset = candidate_pcode->alias->offset;
        if (offset == 0 && candidate_pcode->alias->size == object->type->size)
            flag24 = 1;
    } else if (candidate_pcode->args[2].kind == PCOp_MEMORY) {
        object = candidate_pcode->args[2].data.mem.obj;
        if (candidate_pcode->op == PC_ADDIS)
            offset = candidate_pcode->args[2].data.mem.offset << 16;
        else
            offset = candidate_pcode->args[2].data.mem.offset;
    } else {
        return 0;
    }

    CError_ASSERT(478, object->otype == OT_OBJECT);

    if ((candidate_pcode->flags & (fIsRead | fIsWrite)) && (candidate_pcode->flags & fUpdatesPtr)) {
        reg = candidate_pcode->args[1].data.reg.reg;
        offset = 0;
        flag24 = 1;
    } else if (candidate_pcode->op == PC_LWZ) {
        if (object->datatype != DNONLAZYPTR)
            return 0;

        object = object->u.var.realObj;
        CError_ASSERT(495, object->otype == OT_OBJECT);
        offset = 0;
    } else if (candidate_pcode->op == PC_ADDI) {
        if (!candidate_pcode->alias && object)
            candidate_pcode->alias = make_alias(object, offset, 1);
    } else if (candidate_pcode->op == PC_ADDIS) {
        if (!candidate_pcode->alias && object)
            candidate_pcode->alias = make_alias(object, offset, 1);
    } else if (candidate_pcode->op == PC_ADD) {
        offset = 0;
        flag24 = 1;
    } else {
        CError_FATAL(509);
    }

    if (
        !(use_pcode->flags & (fIsRead | fIsWrite)) &&
        use_pcode->op != PC_ADDI &&
        use_pcode->op != PC_ADD &&
        use_pcode->op != PC_ADDIS
        ) {
        if (object->datatype == DLOCAL && !is_safe_const(object))
            add_alias_member(worst_case, make_alias(object, 0, 0));
        return 1;
    }

    if (
        (use_pcode->flags & (fIsWrite | fPCodeFlag40000)) &&
        use_pcode->args[0].kind == PCOp_REGISTER &&
        use_pcode->args[0].arg == RegClass_GPR &&
        use_pcode->args[0].data.reg.reg == reg &&
        object->datatype == DLOCAL &&
        !is_safe_const(object)
        )
        add_alias_member(worst_case, make_alias(object, 0, 0));

    if (use_pcode->argCount < 3)
        return 1;

    CError_ASSERT(543, use_pcode->args[1].kind == PCOp_REGISTER);

    if (candidate_pcode->block == use_pcode->block && precedes(candidate_pcode, use_pcode)) {
        for (scan = candidate_pcode->nextPCode; scan && scan != use_pcode; scan = scan->nextPCode) {
            for (op = scan->args, i = scan->argCount; i--; op++) {
                if (op->kind == PCOp_REGISTER &&
                    op->arg == RegClass_GPR &&
                    (op->data.reg.effect & EffectWrite) &&
                    op->data.reg.reg == reg)
                    return 1;
            }
        }
    } else {
        if (!bitvectorgetbit(candidateID, propinfo[use_pcode->block->blockIndex].vec8)) {
            if (bitvectorgetbit(candidate_pcode->defID, usedefinfo[use_pcode->block->blockIndex].defvec8)) {
                for (scan = use_pcode->block->firstPCode; scan && scan != use_pcode; scan = scan->nextPCode) {
                    for (op = scan->args, i = scan->argCount; i--; op++) {
                        if (op->kind == PCOp_REGISTER &&
                            op->arg == RegClass_GPR &&
                            (op->data.reg.effect & EffectWrite) &&
                            op->data.reg.reg == reg)
                            return 1;
                    }
                }
            } else {
                return 1;
            }
        }

        for (scan = use_pcode->block->firstPCode; scan; scan = scan->nextPCode) {
            if (scan == use_pcode)
                break;
            for (op = scan->args, i = scan->argCount; i--; op++) {
                if (op->kind == PCOp_REGISTER &&
                    op->arg == RegClass_GPR &&
                    (op->data.reg.effect & EffectWrite) &&
                    op->data.reg.reg == reg)
                    return 1;
            }
        }
    }

    CError_ASSERT(598, object != NULL);

    if (use_pcode->op == PC_ADDI || use_pcode->op == PC_ADD || use_pcode->op == PC_ADDIS) {
        if (use_pcode->args[0].data.reg.reg < n_real_registers[RegClass_GPR] && !is_safe_const(object))
            add_alias_member(worst_case, make_alias(object, 0, 0));
    }

    if (use_pcode->flags & (fIsRead | fIsWrite))
        size = nbytes_loaded_or_stored_by(use_pcode);

    if (use_pcode->args[2].kind == PCOp_REGISTER) {
        if (use_pcode->args[1].data.reg.reg == 0) {
            if (use_pcode->args[2].data.reg.reg == reg)
                alias = make_alias(object, offset, size);
        } else {
            if (use_pcode->args[1].data.reg.reg == reg)
                reg2 = use_pcode->args[2].data.reg.reg;
            else if (use_pcode->args[2].data.reg.reg == reg)
                reg2 = use_pcode->args[1].data.reg.reg;
            else
                return 1;

            for (scan = use_pcode->prevPCode; scan; scan = scan->prevPCode) {
                if (scan->op == PC_LI && scan->args[0].data.reg.reg == reg2)
                    break;

                for (i = 0; i < scan->argCount; i++) {
                    if (scan->args[i].kind == PCOp_REGISTER &&
                        scan->args[i].arg == RegClass_GPR &&
                        scan->args[i].data.reg.reg == reg2 &&
                        (scan->args[i].data.reg.effect & EffectWrite)) {
                        scan = NULL;
                        break;
                    }
                }

                if (!scan)
                    break;
            }

            if (scan) {
                offset += scan->args[1].data.mem.offset;
                alias = make_alias(object, offset, size);
            } else {
                alias = make_alias(object, 0, 0);
            }
        }
    } else {
        if (use_pcode->args[1].kind != PCOp_REGISTER ||
            use_pcode->args[1].arg != RegClass_GPR ||
            use_pcode->args[1].data.reg.reg != reg)
            return 1;

        if (use_pcode->args[1].data.reg.effect & EffectWrite) {
            alias = make_alias(object, 0, 0);
        } else if (use_pcode->args[2].kind == PCOp_IMMEDIATE) {
            if (use_pcode->op == PC_ADDIS) {
                offset += use_pcode->args[2].data.imm.value << 16;
                alias = make_alias(object, offset, 1);
            } else {
                offset += use_pcode->args[2].data.imm.value;
                alias = make_alias(object, offset, size);
            }
        } else {
            return 1;
        }
    }

    if (flag24)
        alias = make_alias(object, 0, 0);

    if (!alias)
        return 1;

    if (!use_pcode->alias) {
        if (
            use_pcode->op == PC_ADDI ||
            use_pcode->op == PC_ADD ||
            use_pcode->op == PC_ADDIS ||
            ((candidate_pcode->flags & (fIsRead | fIsWrite)) && (candidate_pcode->flags & fUpdatesPtr))
            )
            recursive_propagation = 1;
    }

    if (use_pcode->alias) {
        if (use_pcode->alias == worst_case) {
            add_alias_member(worst_case, make_alias(object, 0, 0));
        } else if (use_pcode->alias == alias) {
            return 1;
        } else if (use_pcode->alias->type == AliasType0 || use_pcode->alias->type == AliasType1) {
            if (object == use_pcode->alias->object) {
                use_pcode->alias = make_alias(object, 0, 0);
            } else {
                aliasSet = make_alias_set();
                if (
                    use_pcode->op == PC_ADDI ||
                    use_pcode->op == PC_ADD ||
                    use_pcode->op == PC_ADDIS ||
                    ((use_pcode->flags & (fIsRead | fIsWrite)) && (use_pcode->flags & fUpdatesPtr))
                    ) {
                    if (alias->type == AliasType2)
                        add_alias_member(worst_case, alias);
                    else
                        add_alias_member(worst_case, make_alias(use_pcode->alias->object, 0, 0));
                }
                add_alias_member(aliasSet, use_pcode->alias);
                add_alias_member(aliasSet, alias);
                use_pcode->alias = aliasSet;
            }
        } else {
            add_alias_member(use_pcode->alias, alias);
        }
    } else {
        use_pcode->alias = alias;
    }

    propagated_instructions = 1;
    return 1;
}

static void finishpropagatealiases(int id) {
    propagated_instructions = 1;
}

static Propagation alias_prop = {
    &is_address_load,
    &addresspropagatestouse,
    &finishpropagatealiases,
    "ALIAS",
    "ALIASES",
    "A%" PRId32,
    1
};

static void propagatealiasinfo(Object *proc) {
    propagateinstructions(proc, &alias_prop, (copts.optimizationlevel >= 4) ? 4 : 1, 1);
}

void gather_alias_info(void) {
    UInt32 *myvec; // r31
    Alias *alias; // r22
    AliasMember *member;
    AliasMember *member2;
    PCodeBlock *block; // r21
    PCode *pcode; // r20
    PCodeArg *op; // r19
    RegUseOrDef *list; // r18
    int i; // r17
    Alias *alias_choice; // r16
    int aliases_idx; // r15 (helper in r23)
    PCode *defpcode; // r14
    Alias *alias_array[3];
    UseOrDef *def;
    int defID;

    if (coloring) {
        propagatealiasinfo(gFunction);
        myvec = oalloc(4 * ((number_of_Defs + 31) >> 5));

        for (block = pcbasicblocks; block; block = block->nextBlock) {
            bitvectorcopy(myvec, usedefinfo[block->blockIndex].defvec8, number_of_Defs);

            for (pcode = block->firstPCode; pcode; pcode = pcode->nextPCode) {
                if (pcode->flags & (fIsRead | fIsWrite | fPCodeFlag20000 | fPCodeFlag40000)) {
                    if (!pcode->alias) {
                        pcode->alias = worst_case;
                    } else {
                        if ((pcode->alias->type == AliasType0 || pcode->alias->type == AliasType1) &&
                            pcode->alias->size == nbytes_loaded_or_stored_by(pcode)) {
                            pcode->flags &= ~fIsPtrOp;
                        } else {
                            pcode->flags |= fIsPtrOp;
                        }

                        if (pcode->alias != worst_case) {
                            aliases_idx = 0;
                            alias_choice = NULL;
                            op = pcode->args;
                            for (i = 0; i < pcode->argCount; i++, op++) {
                                if (
                                    (!(pcode->flags & (fIsWrite | fPCodeFlag40000)) || op != pcode->args) &&
                                    op->kind == PCOp_REGISTER &&
                                    op->arg == RegClass_GPR &&
                                    (op->data.reg.effect & EffectRead)
                                    ) {
                                    alias_array[aliases_idx] = NULL;
                                    if (aliases_idx >= 2) {
                                        alias_choice = worst_case;
                                        break;
                                    }
                                    alias_array[aliases_idx] = pcode->alias;

                                    for (list = reg_Defs[RegClass_GPR][op->data.reg.reg]; list; list = list->next) {
                                        if (bitvectorgetbit(list->id, myvec)) {
                                            defpcode = Defs[list->id].pcode;
                                            if (!defpcode->alias || !is_address_load(defpcode) || defpcode->alias == worst_case) {
                                                alias_array[aliases_idx] = worst_case;
                                                break;
                                            }
                                        }
                                    }

                                    aliases_idx++;
                                }
                            }

                            if (!alias_choice) {
                                if (aliases_idx > 0) {
                                    alias_choice = alias_array[0];
                                    if (aliases_idx == 2) {
                                        if (alias_array[0] != worst_case) {
                                            if (alias_array[1] != worst_case)
                                                alias_choice = worst_case;
                                        } else if (alias_array[1] != worst_case) {
                                            alias_choice = alias_array[1];
                                        }
                                    }
                                }

                                if (alias_choice == worst_case) {
                                    pcode->flags |= fIsPtrOp;
                                    if (pcode->alias->type == AliasType2)
                                        add_alias_member(worst_case, pcode->alias);
                                    else
                                        add_alias_member(worst_case, make_alias(pcode->alias->object, 0, 0));
                                }

                                if (alias_choice)
                                    pcode->alias = alias_choice;
                            }
                        }
                    }
                } else {
                    if ((pcode->flags & fIsCall) && !pcode->alias)
                        pcode->alias = worst_case;
                }

                for (def = &Defs[defID = pcode->defID]; defID < number_of_Defs && def->pcode == pcode; defID++, def++) {
                    if (def->v.kind == PCOp_REGISTER && def->v.arg == RegClass_GPR) {
                        for (list = reg_Defs[RegClass_GPR][def->v.u.reg]; list; list = list->next)
                            bitvectorclearbit(list->id, myvec);
                    }
                    bitvectorsetbit(defID, myvec);
                }
            }
        }

        freeoheap();
    } else {
        for (block = pcbasicblocks; block; block = block->nextBlock) {
            for (pcode = block->firstPCode; pcode; pcode = pcode->nextPCode) {
                if ((pcode->flags & (fIsRead | fIsWrite | fIsCall | fPCodeFlag20000 | fPCodeFlag40000)) && !pcode->alias)
                    pcode->alias = worst_case;
            }
        }
    }

    if (n_gathered_aliases != n_aliases) {
        for (alias = aliases; alias; alias = alias->next) {
            if (alias->type == AliasType2) {
                alias->vec24 = lalloc(4 * ((n_aliases + 31) >> 5));
                bitvectorinitialize(alias->vec24, n_aliases, 0);
                for (member = alias->parents; member; member = member->nextParent) {
                    bitvectorsetbit(member->child->index, alias->vec24);
                    for (member2 = member->child->parents; member2; member2 = member2->nextParent)
                        bitvectorsetbit(member2->child->index, alias->vec24);
                }
            }
        }
        n_gathered_aliases = n_aliases;
    }
}

static Boolean may_alias_alias(Alias *a, Alias *b) {
    switch ((a->type * 3) + b->type) {
        case (AliasType0 * 3) + AliasType0:
            return a == b;
        case (AliasType0 * 3) + AliasType1:
        case (AliasType1 * 3) + AliasType0:
            return a->object == b->object;
        case (AliasType1 * 3) + AliasType1:
            return (a->object == b->object) && aliases_overlap(a, b);
        case (AliasType0 * 3) + AliasType2:
        case (AliasType1 * 3) + AliasType2:
            return bitvectorgetbit(a->index, b->vec24) != 0;
        case (AliasType2 * 3) + AliasType0:
        case (AliasType2 * 3) + AliasType1:
            return bitvectorgetbit(b->index, a->vec24) != 0;
        case (AliasType2 * 3) + AliasType2:
            return (a == b) || !bitvectorintersectionisempty(a->vec24, b->vec24, n_aliases);
        default:
            CError_FATAL(1054);
            return 1;
    }
}

Boolean may_alias(PCode *a, PCode *b) {
    return may_alias_alias(a->alias, b->alias);
}

Boolean uniquely_aliases(PCode *a, PCode *b) {
    if (may_alias_alias(a->alias, b->alias)) {
        if (
            a->alias->type != AliasType2 &&
            b->alias->type != AliasType2 &&
            a->alias &&
            b->alias &&
            a->alias->size == nbytes_loaded_or_stored_by(a) &&
            b->alias->size == nbytes_loaded_or_stored_by(b)
            )
            return 1;
    }

    return 0;
}

Boolean may_alias_worst_case(PCode *pcode) {
    return may_alias_alias(pcode->alias, worst_case);
}

Boolean may_alias_object(PCode *pcode, Object *object) {
    return may_alias_alias(pcode->alias, make_alias(object, 0, 0));
}

void initialize_alias_values(void) {
    Alias *alias;

    for (alias = aliases; alias; alias = alias->next) {
        alias->valuenumber = nextvaluenumber++;
        alias->valuepcode = NULL;
    }
}

void update_alias_value(Alias *alias, PCode *pcode) {
    AliasMember *member;
    AliasMember *member2;
    AliasMember *member3;

    switch (alias->type) {
        case AliasType0:
            killmemory(alias, pcode);
            for (member = alias->children; member; member = member->nextChild) {
                CError_ASSERT(1152, member->parent->type == AliasType2);
                killmemory(member->parent, NULL);
            }
            for (member = alias->parents; member; member = member->nextParent) {
                CError_ASSERT(1157, member->child->type == AliasType1);
                killmemory(member->child, NULL);
                for (member2 = member->child->children; member2; member2 = member2->nextChild) {
                    if (member2->parent != alias) {
                        CError_ASSERT(1163, member2->parent->type == AliasType2);
                        killmemory(member2->parent, NULL);
                    }
                }
            }
            break;

        case AliasType1:
            killmemory(alias, pcode);
            for (member = alias->children; member; member = member->nextChild) {
                killmemory(member->parent, NULL);
                if (member->parent->type == AliasType0) {
                    for (member2 = member->parent->parents; member2; member2 = member2->nextParent) {
                        if (member2->child != alias && aliases_overlap(alias, member2->child)) {
                            killmemory(member2->child, NULL);
                        }
                    }
                }
            }
            break;

        case AliasType2:
            killmemory(alias, NULL);
            for (member = alias->parents; member; member = member->nextParent) {
                killmemory(member->child, NULL);
                for (member2 = member->child->children; member2; member2 = member2->nextChild) {
                    if (member2->parent != alias)
                        killmemory(member2->parent, NULL);
                }
                for (member3 = member->child->parents; member3; member3 = member3->nextParent) {
                    killmemory(member3->child, NULL);
                    for (member2 = member3->child->children; member2; member2 = member2->nextChild) {
                        if (member2->parent != member->child)
                            killmemory(member2->parent, NULL);
                    }
                }
            }
            break;
    }
}

void update_all_alias_values(void) {
    Alias *alias;

    for (alias = aliases; alias; alias = alias->next)
        killmemory(alias, NULL);
}