MWCC/compiler_and_linker/unsorted/IroCSE.c

#include "compiler/IroCSE.h"
#include "compiler/IroDump.h"
#include "compiler/IroFlowgraph.h"
#include "compiler/IroLinearForm.h"
#include "compiler/IroMalloc.h"
#include "compiler/IroPointerAnalysis.h"
#include "compiler/IroSubable.h"
#include "compiler/IroUtil.h"
#include "compiler/IroVars.h"
#include "compiler/CError.h"
#include "compiler/CExpr.h"
#include "compiler/CInt64.h"
#include "compiler/CParser.h"
#include "compiler/CompilerTools.h"
#include "compiler/objects.h"

BitVector *IRO_Depends;
Boolean IRO_NotSubable;
Boolean IRO_IsVolatile;
Boolean IRO_CouldError;
IROExpr *IRO_FirstExpr;
IROExpr *IRO_LastExpr;
SInt32 IRO_NumExprs;
static Boolean HasVectorOperand;

// forward decls
static void IRO_DependsOnForDataFlow(IROLinear *linear, Boolean flag);

static void GetDependsOfIndirect(IROLinear *nd) {
    IROListNode *resultList;
    IROListNode *next;
    IROListNode *list;
    IROListNode *scan;
    IROLinear *scannd;
    Object *obj;
    VarRecord *var;
    int index;
    Boolean result;
    Boolean foundObjRef;

    result = 0;

    if (nd && copts.opt_pointer_analysis && nd->pointsToFunction && FunctionName) {
        resultList = NULL;
        PointerAnalysis_LookupLinearNodePointerExpr(FunctionName, nd, &resultList);
        if ((list = resultList)) {
            for (scan = list; scan; scan = scan->nextList) {
                if (!scan->list.head || !scan->list.tail) {
                    result = 1;
                    break;
                }

                foundObjRef = 0;
                for (scannd = scan->list.head; scannd != scan->list.tail->next; scannd = scannd->next) {
                    if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                        foundObjRef = 1;
                        break;
                    }
                }

                if (!foundObjRef) {
                    result = 1;
                    break;
                }
            }

            if (!result) {
                while (list) {
                    for (scannd = list->list.head; scannd != list->list.tail->next; scannd = scannd->next) {
                        if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                            obj = scannd->u.node->data.objref;
#line 119
                            CError_ASSERT(obj != NULL);
                            var = IRO_FindVar(obj, 1, 1);
#line 121
                            CError_ASSERT(var != NULL);
                            index = var->index;
#line 123
                            CError_ASSERT(index != 0);

                            if (is_volatile_object(obj)) {
                                IRO_IsVolatile = 1;
                                IRO_NotSubable = 1;
                            }
                            Bv_SetBit(index, IRO_Depends);
                        }
                    }
                    list = list->nextList;
                }
            }

            while (resultList) {
                next = resultList->nextList;
                IRO_free(resultList);
                resultList = next;
            }
        } else {
            result = 1;
        }
    } else {
        result = 1;
    }

    if (result) {
        nd = nd->u.monadic;
        if (nd->type == IROLinearOp1Arg && nd->nodetype == EBITFIELD)
            nd = nd->u.monadic;

        if (nd->type == IROLinearOp2Arg && nd->nodetype == EADD) {
            IRO_BaseTerms = 0;
            IRO_VarTerms = 0;
            IRO_DecomposeAddressExpression_Cheap(nd);
            if (IRO_BaseTerms != 1) {
                IRO_CouldError = 1;
                Bv_SetBit(0, IRO_Depends);
                Bv_Or(IRO_FuncKills, IRO_Depends);
            }
            if (IRO_VarTerms)
                IRO_CouldError = 1;
        } else {
            IRO_CouldError = 1;
            Bv_SetBit(0, IRO_Depends);
            Bv_Or(IRO_FuncKills, IRO_Depends);
        }
    }
}

static void GetDependsOfFunctionCallForDataFlow(IROLinear *nd) {
    IROLinear *innernd;
    IROListNode *resultList;
    IROListNode *next;
    IROListNode *list;
    IROListNode *scan;
    IROLinear *scannd;
    Object *obj;
    VarRecord *var;
    int index;
    Boolean result;
    Boolean foundObjRef;
    ObjectList *olist;
    ObjectList *depsList;

    result = 0;
    innernd = nd->u.funccall.linear8;

    if (innernd && copts.opt_pointer_analysis && innernd->pointsToFunction && FunctionName) {
        resultList = NULL;
        PointerAnalysis_LookupLinearNodePointerExpr(FunctionName, innernd, &resultList);
        if ((list = resultList)) {
            for (scan = list; scan; scan = scan->nextList) {
                if (!scan->list.head || !scan->list.tail) {
                    result = 1;
                    break;
                }

                foundObjRef = 0;
                for (scannd = scan->list.head; scannd != scan->list.tail->next; scannd = scannd->next) {
                    if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                        foundObjRef = 1;
                        obj = scannd->u.node->data.objref;
#line 234
                        CError_ASSERT(obj != NULL);

                        depsList = NULL;
                        PointerAnalysis_GetFunctionDependencies(obj, nd, &depsList);

                        for (olist = depsList; olist; olist = olist->next) {
                            if (!olist->object) {
                                result = 1;
                                break;
                            }
                        }

                        while (depsList) {
                            olist = depsList->next;
                            IRO_free(depsList);
                            depsList = olist;
                        }

                        if (result)
                            break;
                    }
                }

                if (!foundObjRef)
                    result = 1;
                if (result)
                    break;
            }

            if (!result) {
                for (list = resultList; list; list = list->nextList) {
                    for (scannd = list->list.head; scannd != list->list.tail->next; scannd = scannd->next) {
                        if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                            obj = scannd->u.node->data.objref;

                            depsList = NULL;
                            PointerAnalysis_GetFunctionDependencies(obj, nd, &depsList);

                            for (olist = depsList; olist; olist = olist->next) {
                                var = IRO_FindVar(olist->object, 1, 1);
#line 285
                                CError_ASSERT(var != NULL);
                                index = var->index;
#line 287
                                CError_ASSERT(index != 0);

                                if (is_volatile_object(olist->object)) {
                                    IRO_IsVolatile = 1;
                                    IRO_NotSubable = 1;
                                }
                                Bv_SetBit(index, IRO_Depends);
                            }

                            while (depsList) {
                                olist = depsList->next;
                                IRO_free(depsList);
                                depsList = olist;
                            }
                        }
                    }
                }
            }

            while (resultList) {
                next = resultList->nextList;
                IRO_free(resultList);
                resultList = next;
            }
        } else {
            result = 1;
        }
    } else {
        result = 1;
    }

    if (result) {
        IRO_DependsOnForDataFlow(nd->u.funccall.linear8, 0);
        Bv_Or(IRO_FuncKills, IRO_Depends);

        for (index = nd->u.funccall.argCount - 1; index >= 0; index--)
            IRO_DependsOnForDataFlow(nd->u.funccall.args[index], 0);
    }
}

static void IRO_DependsOn(IROLinear *linear, Boolean flag) {
    VarRecord *var;
    IROLinear *inner;

    if (linear->rtype && CParser_IsVolatile(linear->rtype, linear->nodeflags & ENODE_FLAG_QUALS)) {
        IRO_IsVolatile = 1;
        IRO_NotSubable = 1;
    }

    if (!IRO_NotSubable) {
        switch (linear->type) {
            case IROLinearOperand:
                if (flag && linear->u.node->type == EOBJREF) {
                    if ((var = IRO_FindVar(linear->u.node->data.objref, 0, 1))) {
                        if (is_volatile_object(var->object)) {
                            IRO_IsVolatile = 1;
                            IRO_NotSubable = 1;
                        }
                        Bv_SetBit(var->index, IRO_Depends);
                    } else {
                        IRO_NotSubable = 1;
                    }
                }
                break;
            case IROLinearOp1Arg:
                if (IRO_IsAssignOp[linear->nodetype]) {
                    IRO_NotSubable = 1;
                } else {
                    inner = linear->u.monadic;
                    if (linear->nodetype == EINDIRECT) {
                        if (inner->type == IROLinearOp1Arg && inner->nodetype == EBITFIELD)
                            inner = inner->u.monadic;
                        if (inner->type != IROLinearOperand || inner->u.node->type != EOBJREF)
                            GetDependsOfIndirect(linear);
                    }

                    IRO_DependsOn(inner, linear->nodetype == EINDIRECT);
                }
                break;
            case IROLinearOp2Arg:
                if (IRO_IsAssignOp[linear->nodetype]) {
                    IRO_NotSubable = 1;
                } else {
                    if (linear->nodetype == EDIV || linear->nodetype == EMODULO) {
                        if (IRO_IsIntConstant(linear->u.diadic.right)) {
                            if (CInt64_Equal(linear->u.diadic.right->u.node->data.intval, cint64_zero))
                                IRO_CouldError = 1;
                        } else {
                            IRO_CouldError = 1;
                        }
                    }

                    IRO_DependsOn(linear->u.diadic.left, flag);
                    IRO_DependsOn(linear->u.diadic.right, flag);
                }
                break;
            case IROLinearOp3Arg:
                if (IRO_IsAssignOp[linear->nodetype]) {
                    IRO_NotSubable = 1;
                } else {
                    IRO_DependsOn(linear->u.args3.a, flag);
                    IRO_DependsOn(linear->u.args3.b, flag);
                    IRO_DependsOn(linear->u.args3.c, flag);
                }
                break;
            case IROLinearFunccall:
                IRO_NotSubable = 1;
                break;
            default:
#line 479
                CError_FATAL();
        }
    }
}

static void IRO_DependsOnForDataFlow(IROLinear *linear, Boolean flag) {
    VarRecord *var;
    IROLinear *inner;

    if (linear->rtype && CParser_IsVolatile(linear->rtype, linear->nodeflags & ENODE_FLAG_QUALS)) {
        IRO_IsVolatile = 1;
        IRO_NotSubable = 1;
    }

    switch (linear->type) {
        case IROLinearOperand:
            if (flag && linear->u.node->type == EOBJREF) {
                if ((var = IRO_FindVar(linear->u.node->data.objref, 0, 1))) {
                    if (is_volatile_object(var->object)) {
                        IRO_IsVolatile = 1;
                        IRO_NotSubable = 1;
                    }
                    Bv_SetBit(var->index, IRO_Depends);
                } else {
                    IRO_NotSubable = 1;
                }
            }
            break;
        case IROLinearOp1Arg:
            if (IRO_IsAssignOp[linear->nodetype])
                IRO_NotSubable = 1;

            inner = linear->u.monadic;
            if (linear->nodetype == EINDIRECT) {
                if (inner->type == IROLinearOp1Arg && inner->nodetype == EBITFIELD)
                    inner = inner->u.monadic;
                if (inner->type != IROLinearOperand || inner->u.node->type != EOBJREF)
                    GetDependsOfIndirect(linear);
            }

            IRO_DependsOnForDataFlow(inner, linear->nodetype == EINDIRECT);
            break;
        case IROLinearOp2Arg:
            if (IRO_IsAssignOp[linear->nodetype])
                IRO_NotSubable = 1;

            if (linear->nodetype == EDIV || linear->nodetype == EMODULO) {
                if (IRO_IsIntConstant(linear->u.diadic.right)) {
                    if (CInt64_Equal(linear->u.diadic.right->u.node->data.intval, cint64_zero))
                        IRO_CouldError = 1;
                } else {
                    IRO_CouldError = 1;
                }
            }

            IRO_DependsOnForDataFlow(linear->u.diadic.left, flag);
            IRO_DependsOnForDataFlow(linear->u.diadic.right, flag);
            break;
        case IROLinearOp3Arg:
            if (IRO_IsAssignOp[linear->nodetype])
                IRO_NotSubable = 1;

            IRO_DependsOnForDataFlow(linear->u.args3.a, flag);
            IRO_DependsOnForDataFlow(linear->u.args3.b, flag);
            IRO_DependsOnForDataFlow(linear->u.args3.c, flag);
            break;
        case IROLinearFunccall:
            IRO_NotSubable = 1;
            GetDependsOfFunctionCallForDataFlow(linear);
            break;
        default:
#line 650
            CError_FATAL();
    }
}

void IRO_FindDepends_NoAlloc(IROLinear *linear) {
    Bv_Clear(IRO_Depends);
    IRO_CouldError = 0;
    IRO_NotSubable = 0;
    IRO_IsVolatile = 0;
    IRO_DependsOnForDataFlow(linear, 0);
}

void IRO_FindDepends(IROLinear *linear) {
    Bv_AllocVector(&IRO_Depends, IRO_NumVars + 1);
    IRO_CouldError = 0;
    IRO_NotSubable = 0;
    IRO_DependsOn(linear, 0);
}

static void VecAct(IROLinear *linear, Boolean isFirst) {
    if (!isFirst && (linear->flags & IROLF_VecOpBase))
        HasVectorOperand = 1;
}

static Boolean IRO_DoesNotHaveVectorOperand(IROLinear *linear) {
    HasVectorOperand = 0;
    IRO_WalkTree(linear, VecAct);
    return HasVectorOperand == 0;
}

static void IRO_AddExpression(IROLinear *linear, IRONode *node, Boolean flag) {
    IROExpr *expr;

    if ((linear->flags & IROLF_Reffed) && IRO_IsSubableExpression(linear) && IRO_DoesNotHaveVectorOperand(linear)) {
        expr = oalloc(sizeof(IROExpr));
        expr->x0 = 0;
        expr->index = ++IRO_NumExprs;
        expr->linear = linear;
        expr->x8 = NULL;
        expr->node = node;
        IRO_FindDepends(linear);
        expr->depends = IRO_Depends;
        expr->notSubable = IRO_NotSubable;
        expr->couldError = IRO_CouldError;
        expr->next = NULL;
        expr->x14 = NULL;
        if (IRO_FirstExpr)
            IRO_LastExpr->next = expr;
        else
            IRO_FirstExpr = expr;
        IRO_LastExpr = expr;
        linear->expr = expr;
    }
}

void IRO_FindExpressions(BitVector *bv, Boolean flag) {
    IROLinear *nd;
    IRONode *fnode;

    IRO_FirstExpr = IRO_LastExpr = NULL;
    IRO_NumExprs = 0;

    for (fnode = IRO_FirstNode; fnode; fnode = fnode->nextnode) {
        if (!bv || Bv_IsBitSet(fnode->index, bv)) {
            for (nd = fnode->first; nd; nd = nd->next) {
                nd->expr = NULL;
                IRO_AddExpression(nd, fnode, flag);
                if (nd == fnode->last)
                    break;
            }
        } else {
            for (nd = fnode->first; nd; nd = nd->next) {
                nd->expr = NULL;
                if (nd == fnode->last)
                    break;
            }
        }
    }

    IRO_CheckForUserBreak();
}

void IRO_RemoveExpr(IROExpr *expr) {
    IROExpr *prev;
    IROExpr *scan;

    scan = IRO_FirstExpr;
    prev = NULL;
    while (scan != expr) {
        prev = scan;
        scan = scan->next;
#line 809
        CError_ASSERT(scan);
    }

    expr->linear->expr = NULL;
    if (prev)
        prev->next = expr->next;
    else
        IRO_FirstExpr = expr->next;
}

static void GetExprKillsByIndirectAssignment(IROLinear *linear) {
    IROLinear *inner;
    IROListNode *resultList;
    IROListNode *next;
    IROListNode *list;
    IROListNode *scan;
    IROLinear *scannd;
    Object *obj;
    VarRecord *var;
    int index;
    Boolean result;
    Boolean foundObjRef;
    IROExpr *expr;

    result = 0;
    if (linear->type == IROLinearOp2Arg)
        linear = linear->u.diadic.left;
    else
        linear = linear->u.monadic;

    if (
        linear &&
        linear->type == IROLinearOp1Arg &&
        linear->nodetype == EINDIRECT &&
        (inner = linear->u.monadic) &&
        copts.opt_pointer_analysis &&
        inner->pointsToFunction &&
        FunctionName
        ) {
        resultList = NULL;
        PointerAnalysis_LookupLinearNodePointerExpr(FunctionName, inner, &resultList);
        if ((list = resultList)) {
            for (scan = list; scan; scan = scan->nextList) {
                if (!scan->list.head || !scan->list.tail) {
                    result = 1;
                    break;
                }

                foundObjRef = 0;
                for (scannd = scan->list.head; scannd != scan->list.tail->next; scannd = scannd->next) {
                    if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                        foundObjRef = 1;
                        break;
                    }
                }

                if (!foundObjRef) {
                    result = 1;
                    break;
                }
            }

            if (!result) {
                while (list) {
                    for (scannd = list->list.head; scannd != list->list.tail->next; scannd = scannd->next) {
                        if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                            obj = scannd->u.node->data.objref;
#line 893
                            CError_ASSERT(obj != NULL);
                            var = IRO_FindVar(obj, 1, 1);
#line 895
                            CError_ASSERT(var != NULL);
                            index = var->index;

                            for (expr = IRO_FirstExpr; expr; expr = expr->next) {
                                if (Bv_IsBitSet(index, expr->depends))
                                    Bv_SetBit(expr->index, IRO_ExprKills);
                            }
                        }
                    }
                    list = list->nextList;
                }
            }

            while (resultList) {
                next = resultList->nextList;
                IRO_free(resultList);
                resultList = next;
            }
        } else {
            result = 1;
        }
    } else {
        result = 1;
    }

    if (result) {
        for (expr = IRO_FirstExpr; expr; expr = expr->next) {
            if (Bv_BitsInCommon(expr->depends, IRO_FuncKills))
                Bv_SetBit(expr->index, IRO_ExprKills);
        }
    }
}

static void GetExprKillsByFunctionCall(IROLinear *funccall) {
    IROLinear *innernd;
    IROListNode *resultList;
    IROListNode *next;
    IROListNode *list;
    IROListNode *scan;
    IROLinear *scannd;
    Object *obj;
    VarRecord *var;
    int index;
    Boolean result;
    Boolean foundObjRef;
    ObjectList *olist;
    ObjectList *depsList;
    IROExpr *expr;

    result = 0;
    innernd = funccall->u.funccall.linear8;

    if (innernd && copts.opt_pointer_analysis && innernd->pointsToFunction && FunctionName) {
        resultList = NULL;
        PointerAnalysis_LookupLinearNodePointerExpr(FunctionName, innernd, &resultList);
        if ((list = resultList)) {
            for (scan = list; scan; scan = scan->nextList) {
                if (!scan->list.head || !scan->list.tail) {
                    result = 1;
                    break;
                }

                foundObjRef = 0;
                for (scannd = scan->list.head; scannd != scan->list.tail->next; scannd = scannd->next) {
                    if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                        foundObjRef = 1;
                        obj = scannd->u.node->data.objref;
#line 991
                        CError_ASSERT(obj != NULL);

                        depsList = NULL;
                        PointerAnalysis_GetFunctionKills(obj, funccall, &depsList);

                        for (olist = depsList; olist; olist = olist->next) {
                            if (!olist->object) {
                                result = 1;
                                break;
                            }
                        }

                        while (depsList) {
                            olist = depsList->next;
                            IRO_free(depsList);
                            depsList = olist;
                        }

                        if (result)
                            break;
                    }
                }

                if (!foundObjRef)
                    result = 1;
                if (result)
                    break;
            }

            if (!result) {
                for (list = resultList; list; list = list->nextList) {
                    for (scannd = list->list.head; scannd != list->list.tail->next; scannd = scannd->next) {
                        if (scannd->type == IROLinearOperand && scannd->u.node->type == EOBJREF) {
                            obj = scannd->u.node->data.objref;

                            depsList = NULL;
                            PointerAnalysis_GetFunctionKills(obj, funccall, &depsList);

                            for (olist = depsList; olist; olist = olist->next) {
                                var = IRO_FindVar(olist->object, 1, 1);
#line 1042
                                CError_ASSERT(var != NULL);
                                index = var->index;
#line 1044
                                CError_ASSERT(index != 0);

                                for (expr = IRO_FirstExpr; expr; expr = expr->next) {
                                    if (Bv_IsBitSet(index, expr->depends))
                                        Bv_SetBit(expr->index, IRO_ExprKills);
                                }
                            }

                            while (depsList) {
                                olist = depsList->next;
                                IRO_free(depsList);
                                depsList = olist;
                            }
                        }
                    }
                }
            }

            while (resultList) {
                next = resultList->nextList;
                IRO_free(resultList);
                resultList = next;
            }
        } else {
            result = 1;
        }
    } else {
        result = 1;
    }

    if (result) {
        for (expr = IRO_FirstExpr; expr; expr = expr->next) {
            if (Bv_BitsInCommon(expr->depends, IRO_FuncKills))
                Bv_SetBit(expr->index, IRO_ExprKills);
        }
    }
}

static void IRO_GetExprKills(IROLinear *linear) {
    Bv_Clear(IRO_ExprKills);
    switch (linear->type) {
        case IROLinearOp1Arg:
        case IROLinearOp2Arg:
            if (IRO_IsAssignOp[linear->nodetype]) {
                VarRecord *var;
                int index;

                var = IRO_FindAssigned(linear);
                index = 0;
                if (var)
                    index = var->index;
                if (!index) {
                    GetExprKillsByIndirectAssignment(linear);
                } else {
                    IROExpr *expr;
                    for (expr = IRO_FirstExpr; expr; expr = expr->next) {
                        if (Bv_IsBitSet(index, expr->depends))
                            Bv_SetBit(expr->index, IRO_ExprKills);
                    }
                }
            }
            break;
        case IROLinearAsm: {
            IROExpr *expr;
            IRO_GetKills(linear);
            for (expr = IRO_FirstExpr; expr; expr = expr->next) {
                if (Bv_BitsInCommon(expr->depends, IRO_VarKills))
                    Bv_SetBit(expr->index, IRO_ExprKills);
            }
            break;
        }
        case IROLinearFunccall:
            GetExprKillsByFunctionCall(linear);
            break;
    }
}

void IRO_ComputeAvail(void) {
    IRONode *node;
    IROLinear *linear;
    SInt32 counter;
    BitVector *bv;
    Boolean flag;

    counter = 0;
    node = IRO_FirstNode;
    Bv_AllocVector(&IRO_VarKills, IRO_NumVars + 1);
    Bv_AllocVector(&IRO_ExprKills, IRO_NumExprs + 1);

    while (node) {
        Bv_AllocVector(&node->x16, IRO_NumExprs);
        if (node->numpred)
            Bv_Set(node->x16);
        Bv_AllocVector(&node->x22, IRO_NumExprs);
        Bv_AllocVector(&node->x1E, IRO_NumExprs);
        Bv_AllocVector(&node->x1A, IRO_NumExprs);

        for (linear = node->first; linear; linear = linear->next) {
            if (linear->expr)
                Bv_SetBit(linear->expr->index, node->x1E);
            IRO_GetExprKills(linear);
            Bv_Or(IRO_ExprKills, node->x22);
            Bv_Minus(IRO_ExprKills, node->x1E);
            if (linear == node->last)
                break;

            if (counter > 250) {
                IRO_CheckForUserBreak();
                counter = 0;
            } else {
                counter++;
            }
        }

        Bv_Copy(node->x16, node->x1A);
        Bv_Minus(node->x22, node->x1A);
        Bv_Or(node->x1E, node->x1A);
        node = node->nextnode;
    }

    IRO_CheckForUserBreak();

    Bv_AllocVector(&bv, IRO_NumExprs);
    do {
        flag = 0;
        for (node = IRO_FirstNode; node; node = node->nextnode) {
            if (!node->numpred) {
                Bv_Clear(bv);
            } else {
                UInt16 i;
                Bv_Set(bv);
                for (i = 0; i < node->numpred; i++)
                    Bv_And(IRO_NodeTable[node->pred[i]]->x1A, bv);
            }

            if (!Bv_Compare(bv, node->x16)) {
                flag = 1;
                Bv_Copy(bv, node->x16);
            }

            Bv_Copy(node->x16, node->x1A);
            Bv_Minus(node->x22, node->x1A);
            Bv_Or(node->x1E, node->x1A);
        }
        IRO_CheckForUserBreak();
    } while (flag);
}

static void IRO_MakeReplacementEmbedded(IROExpr *expr) {
    IROLinear *opnd;
    IROLinear *ind;
    IROLinear *ass;

    IRO_GetTemp(expr);

    opnd = IRO_NewLinear(IROLinearOperand);
    opnd->u.node = create_objectrefnode(expr->x8);
    opnd->rtype = opnd->u.node->data.objref->type;
    opnd->index = ++IRO_NumLinear;
    opnd->flags |= IROLF_Reffed | IROLF_Assigned | IROLF_Ind;

    ind = IRO_NewLinear(IROLinearOp1Arg);
    ind->nodetype = EINDIRECT;
    ind->rtype = expr->linear->rtype;
    ind->u.monadic = opnd;
    ind->index = ++IRO_NumLinear;
    ind->flags |= IROLF_Reffed | IROLF_Assigned;

    ass = IRO_NewLinear(IROLinearOp2Arg);
    ass->nodetype = EASS;
    ass->u.diadic.left = ind;
    ass->u.diadic.right = expr->linear;
    ass->rtype = expr->linear->rtype;
    ass->index = ++IRO_NumLinear;

    opnd->next = ind;
    ind->next = ass;
    IRO_ReplaceReferenceWithNode(expr->linear, ass);
    IRO_PasteAfter(opnd, ass, expr->linear);
}

static void IRO_ActUnmarkSubExpressions(IROLinear *linear, Boolean isFirst) {
    if (isFirst)
        linear->flags &= ~IROLF_8;
}

static void CheckCommonSub(IROLinear *linear) {
    IROExpr *expr;

    for (expr = IRO_FirstExpr; expr; expr = expr->next) {
        if (expr->linear != linear && !expr->x14) {
            if (Bv_IsBitSet(expr->index, IRO_Avail) && !expr->notSubable && IRO_ExprsSame(linear, expr->linear)) {
                IRO_WalkTree(linear, IRO_ActUnmarkSubExpressions);
                linear->flags |= IROLF_8;
                linear->expr->x14 = expr;
                break;
            }
        }
    }
}

static void MoveCommonSub(IROExpr *expr) {
    SInt32 best;
    SInt32 sz1;
    SInt32 sz2;
    SInt32 i1;
    SInt32 i2;
    IROLinear *scan;
    IROLinear *array1[64];
    IROLinear *array2[64];
    IROExpr *scanexpr;

    sz1 = 0;
    scan = expr->linear;
    do {
        scan = IRO_LocateFather(scan);
        if (scan) {
            if (sz1 == 64)
                return;
            array1[sz1++] = scan;
        }
    } while (scan);

    best = -1;
    for (scanexpr = IRO_FirstExpr; scanexpr; scanexpr = scanexpr->next) {
        if (scanexpr->x14 == expr) {
            sz2 = 0;
            scan = scanexpr->linear;
            do {
                scan = IRO_LocateFather(scan);
                if (scan) {
                    if (sz2 == 64)
                        return;
                    array2[sz2++] = scan;
                }
            } while (scan);

            i1 = sz1;
            i2 = sz2;
            while (i1 && i2 && array1[sz1 - 1] == array2[sz2 - 1]) {
                i1--;
                i2--;
            }

            if (i1 != sz1 && i1 > best)
                best = i1;
        }
    }

    if (best < 0) {
        IRO_MakeReplacementEmbedded(expr);
    } else {
        IROLinear *start;
        IROLinear *comma;
        IRO_Dump("Moving common sub from node %d to %d\n", expr->linear->index, array1[best]->index);
        start = IRO_FindStart(array1[best]);
        IRO_GetTemp(expr);
        IRO_ReplaceReference(expr->linear, expr->x8, expr->linear);
        IRO_MoveExpression(expr, start);

        comma = IRO_NewLinear(IROLinearOp2Arg);
        comma->nodetype = ECOMMA;
        comma->rtype = array1[best]->rtype;
        comma->u.diadic.left = IRO_AssignToTemp(expr);
        comma->u.diadic.right = array1[best];
        comma->stmt = array1[best]->stmt;
        IRO_ReplaceReferenceWithNode(array1[best], comma);
        IRO_PasteAfter(comma, comma, array1[best]);
    }
}

static void ReplaceCommonSub(IROLinear *linear) {
    IROExpr *expr = linear->expr->x14;
    if (!expr->x8) {
        MoveCommonSub(expr);
        if (!expr->x8)
            return;
    }

    IRO_Dump("Replacing common sub at %d with %d\n", linear->index, expr->linear->index);
    IRO_ReplaceReference(linear, expr->x8, linear);
    IRO_RemoveExpr(linear->expr);
    IRO_NopOut(linear);
}

void IRO_CommonSubs(void) {
    IRONode *node;
    IROLinear *linear;
    SInt32 counter;

    counter = 0;
    for (node = IRO_FirstNode; node; node = node->nextnode) {
        IRO_Avail = node->x16;
        linear = node->first;
        while (1) {
            if (!linear)
                break;
            if (linear->expr && !linear->expr->notSubable)
                CheckCommonSub(linear);
            if (linear->expr)
                Bv_SetBit(linear->expr->index, IRO_Avail);
            IRO_GetExprKills(linear);
            Bv_Minus(IRO_ExprKills, IRO_Avail);
            if (linear == node->last)
                break;
            if (counter > 250) {
                IRO_CheckForUserBreak();
                counter = 0;
            } else {
                counter++;
            }
            linear = linear->next;
        }
    }

    for (node = IRO_FirstNode; node; node = node->nextnode) {
        for (linear = node->first; linear; linear = linear->next) {
            if (linear->expr && (linear->flags & IROLF_8) && !IRO_HasSideEffect(linear))
                ReplaceCommonSub(linear);
            if (linear == node->last)
                break;
            if (counter > 250) {
                IRO_CheckForUserBreak();
                counter = 0;
            } else {
                counter++;
            }
        }
    }

    IRO_CheckForUserBreak();
}

static Boolean CountThisSubableOperandUse() {
}

static void GetSubableOperandUseCount() {
}

static void IRO_MakeTopLevelExprForSubableOperand(IROLinear *linear) {
    IROLinear *copy = IRO_NewLinear(IROLinearOperand);
    memcpy(copy, linear, sizeof(IROLinear));
    copy->index = ++IRO_NumLinear;

    if (IRO_FirstLinear && IRO_FirstLinear->type == IROLinearNop)
        IRO_PasteAfter(copy, copy, IRO_FirstLinear);
    else
        IRO_Paste(copy, copy, IRO_FirstLinear);
}

void IRO_GenerateTopLevelExprsForSubableOperands(void) {
    IROLinear *nd;
    IRONode *fnode;
    VarRecord *var;
    BitVector *bv;

    Bv_AllocVector(&bv, IRO_NumVars + 1);

    for (fnode = IRO_FirstNode; fnode; fnode = fnode->nextnode) {
        for (nd = fnode->first; nd; nd = nd->next) {
            nd->expr = NULL;
            if ((nd->flags & IROLF_Reffed) && IRO_IsSubableExpression(nd) && IRO_DoesNotHaveVectorOperand(nd)) {
                if (nd->type == IROLinearOperand && nd->u.node && nd->u.node->type == EOBJREF) {
                    if ((var = IRO_FindVar(nd->u.node->data.objref, 0, 1))) {
                        if (!Bv_IsBitSet(var->index, bv)) {
                            IRO_MakeTopLevelExprForSubableOperand(nd);
                            Bv_SetBit(var->index, bv);
                        }
                    }
                }
            }

            if (nd == fnode->last)
                break;
        }
    }
}