ARMv8/src/twopassassembly.c

# include "global.h"
# include "a64instruction.h"
# include "symboltable.h"
//generates assembled code based on two pass assembly method


word assembleBranch(a64inst_instruction *instr){
    word binInstr = 0;
    binInstr += (5^28); //101 start of branch instr
    switch (instr->data.BranchData.BranchType)
    {
    case a64inst_UNCONDITIONAL:
        //000101
        //25-0: sign extended simm26
        binInstr += instr->data.processOpData.unconditionalOffset;
        break;
    case a64inst_REGISTER:
        //10000
        //11111
        //000000
        //9-5: address from register
        //0000
        binInstr += ((instr->processOpData.src)^5);
        break;
    case a64inst_CONDITIONAL:
        // 01010100 
        // 25-5: sign extended offset
        // 4-0: 0{condition}
        binInstr += ((instr->processOpData.offset)^5);
        binInstr += instr->processOpData.cond;
        break;
    default:
        break;
    }
    return binInstr;
}

st* firstPass(a64inst_instruction instrs[], int numInstrs){
    //TODO:
    // -iterate over instructions, adding to symbol table
    // create symbol table and map labels to addresses/lines
    struct st table;
    for(int i=0; i<numInstrs; i++){
        
        // discuss defining a LABEL type
        if(instrs[i].type==a64inst_LABEL){
            st_add(table, &(instrs[i].data.LabelData.label), &i);
        }
    }
    return &table;
}
word dpi(a64inst_instruction cI) {
    word out = 0;
    a64inst_DPImmediateData data = cI.data.DPImmediateData;
    //sf
    out += data.regType*(2^31);
    out += data.processOp*(2^29);
    out += 2^28;
    // if arithmetic
    if (data.DPIOpType == a64inst_DPI_ARITHM) {
        out += 2^24;
        // shift
        if (data.processOpData.arithmData.shiftImmediate){
            out += 2^22;
        }
        out += data.processOpData.arithmData.immediate*(2^10);
        out += data.processOpData.arithmData.src*(2^5);
    }
    // if wide move
    else {
        out += 5*(2^23);
        // hw
        out += data.processOpData.wideMovData.shiftScalar*(2^21);
        out += data.processOpData.wideMovData.immediate*(2^5);
    }
    // destination register
    out += data.dest;
    return out;
}

word dpr(a64inst_instruction cI) {
    word out = 0;
    a64inst_DPRegisterData data = cI.data.DPRegisterData;
    // sf
    int sf = data.regType;
    // bits 27-25
    out += 5*(2^25);
    int m = data.DPROpType;
    int opc = 0;
    int opr = 0;
    int rm = 0;
    int operand = 0;
    int rn = 0;
    int rd = 0;
    // multiply
    if (m == 1) {
        //opc = 0;
        opr = 8;
        if (data.processOpData.multiplydata.negProd) {
            operand += 32;
        }
        operand += data.processOpData.multiplydata.summand;
    }
    // arithmetic and logical
    else {
        // shift
        opr += 2*data.processOpData.arithmLogicData.shiftType;
        // arithmetic
        if (data.processOpData.arithmLogicData.type == 1){
            opr += 8;
        }
        // logical
        else {
            if (data.processOpData.arithmLogicData.negShiftedSrc2) {
                opr += 1;
            }
        }
        operand += data.processOpData.arithmLogicData.shiftAmount;
    }
    rm += data.src1;
    rn += data.src2;
    rd += data.dest;
    out += sf*(2^31);
    out += opc * (2^29);
    out += m* (2^28);
    out += opr * (2^21);
    out += rm * (2^16);
    out += operand * 1024;
    out += rn * 32;
    out += rd;
    return out;
}

word sts(a64inst_instruction cI) {
    a64inst_SingleTransferData data = cI.data.SingleTransferData;
    word out = 0;
    a64inst_SingleDataTransferData data2 = data.processOpData.singleDataTransferData;
    // this deals with every bit in the 31-23 range apart from sf and U
    out += (512+128+64+32)*(2^23);
    int sf = data.regType;
    int u = 0;
    int l = data2.transferType;
    int offset = 0;
    int xn = data2.base;
    int rt = data.target;
    switch (data2.addressingMode) {
        // register offset
        case 2:
            offset += 2074 + 64*data2.a64inst_addressingModeData.offsetReg;
            break;
        // unsigned offset
        case 3:
            offset += data2.a64inst_addressingModeData.unsignedOffset;
            u = 1;
            break;
        // pre/post indexed
        default:
            offset = 1 + data2.addressingMode*2 + data2.a64inst_addressingModeData.indexedOffset*4;
            break;
    }
    out += sf*(2^30);
    out += u*(2^22);
    out += offset*1024;
    out += xn * 32;
    out += rt;
    return out;
}

word ldl(a64inst_instruction cI) {
    word out = 3*(2^27);
    a64inst_SingleTransferData data = cI.data.SingleTransferData;
    int sf = data.regType;
    int simm19 = data.processOpData.loadLiteralData.offset;
    int rt = data.target;
    out += sf * (2^30);
    out += simm19*32;
    out += rt;
    return out;
}

void secondPass(a64inst_instruction instrs[], int numInstrs, st* table, word arr[]){
    //TODO:
    // iterate over instructions again, this time replacing labels
    // with values from symbol table
    // after a line has had all the values replaced, assemble it and append
    int index = 0;
    int lbl = 0;
    for (int i=0; i<numInstrs; i++) {
        a64inst_instruction cI = instrs[i];
        switch (cI.type) {
            case a64inst_DPIMMEDIATE:
                arr[index] = dpi(cI);
                index++;
                break;
            case a64inst_DPREGISTER:
                arr[index] = dpr(cI);
                index++;
                break;
            case a64inst_SINGLETRANSFER:
                arr[index] = sts(cI);
                index++;
                break;
            case a64inst_LOADLITERAL:
                arr[index] = ldl(cI);
                index++;
                break;
            case a64inst_DIRECTIVE:
                arr[index] = cI.data.DirectiveData.value;
                index++;
                break;
            case a64inst_HALT:
                arr[index] = 69*(2^25);
                index++;
                break;
            case a64inst_LABEL:
                lbl++;
                break;
            case a64inst_BRANCH:
                arr[index] = assembleBranch(&cI, table, lbl);
                index++;
            default:
                break;
        }
    }
    return;
}