code.c

#include "code.h"
#include <stdarg.h>

#define GLOBAL_SCOPE 0

void emitComment(FILE* out, const char* msg, ...)
{
    va_list args;

    fprintf(out, "# ");

    va_start(args, msg);
    vfprintf(out, msg, args);
    va_end(args);

    fprintf(out, "\n");
}

static int instr_cnt = 0;

void emitInstruction(FILE* out, const char* msg, ...)
{
    va_list args;

    va_start(args, msg);
    vfprintf(out, msg, args);
    va_end(args);

    instr_cnt++;
}

int resetInstrCnt(void)
{
    int t = instr_cnt;
    instr_cnt = 0;
    return t;
}

void register_name(enum Storage reg, int reg_num, char* reg_name)
{
    char reg_prefix;
    switch (reg) {
    case Temp:
        reg_prefix = 't';
        break;
    case SavedTemp:
        reg_prefix = 's';
        break;
    case Return:
        reg_prefix = 'v';
        break;
    case Argument:
        reg_prefix = 'a';
        break;
    default:
        reg_prefix = '0';
        break;
    }
    sprintf(reg_name, "%c%d", reg_prefix, reg_num);
}

void load_id(FILE* out, Node t, enum Storage reg, int reg_num)
{
    char reg_name[3];
    register_name(reg, reg_num, reg_name);

    if (t->expr == ExprConst) {
        emitInstruction(out, "li    $%s, %d\n", reg_name, t->value.num);
    } else if (t->record->scope == GLOBAL_SCOPE) {
        char addr_reg_name[3];
        register_name(reg, reg_num + 1, addr_reg_name);
        emitInstruction(out, "la    $%s, %s\n", addr_reg_name, t->value.name);
        emitInstruction(out, "lw    $%s, 0($%s)\n", reg_name, addr_reg_name);
    } else {
        int loc = t->record->loc;
        switch (t->storage) {
        case Memory:
            emitInstruction(out, "lw    $%s, %d($fp)\n", reg_name, loc);
            break;
        default:
            break;
        }
    }
}

void store_id(FILE* out, int loc, enum Storage reg, int reg_num)
{
    char reg_name[3];
    register_name(reg, reg_num, reg_name);
    emitInstruction(out, "sw    $%s, %d($fp)\n", reg_name, loc);
}

void exec_binop(FILE* out, Node t,
    enum Storage rst_reg, int rst_reg_num,
    enum Storage opa_reg, int opa_reg_num,
    enum Storage opb_reg, int opb_reg_num)
{
    char opa_reg_name[3];
    char opb_reg_name[3];
    char rst_reg_name[3];
    register_name(opa_reg, opa_reg_num, opa_reg_name);
    register_name(opb_reg, opb_reg_num, opb_reg_name);
    register_name(rst_reg, rst_reg_num, rst_reg_name);

    switch (t->value.op) {
    case OpLessThan:
        emitInstruction(out, "slt   $%s, $%s, $%s\n", rst_reg_name, opa_reg_name, opb_reg_name);
        emitInstruction(out, "andi  $%s, $%s, 0x00ff\n", rst_reg_name, rst_reg_name);
        break;
    case OpLessThanEq:
        emitInstruction(out, "slt   $%s, $%s, $%s\n", rst_reg_name, opb_reg_name, opa_reg_name);
        emitInstruction(out, "xori  $%s, $%s, 0x1\n", rst_reg_name, rst_reg_name);
        emitInstruction(out, "andi  $%s, $%s, 0x00ff\n", rst_reg_name, rst_reg_name);
        break;
    case OpGreaterThan:
        emitInstruction(out, "slt   $%s, $%s, $%s\n", rst_reg_name, opb_reg_name, opa_reg_name);
        emitInstruction(out, "andi  $%s, $%s, 0x00ff\n", rst_reg_name, rst_reg_name);
        break;
    case OpGreaterThanEq:
        emitInstruction(out, "slt   $%s, $%s, $%s\n", rst_reg_name, opa_reg_name, opb_reg_name);
        emitInstruction(out, "xori  $%s, $%s, 0x1\n", rst_reg_name, rst_reg_name);
        emitInstruction(out, "andi  $%s, $%s, 0x00ff\n", rst_reg_name, rst_reg_name);
        break;
    case OpEqual:
        emitInstruction(out, "xor   $%s, $%s, $%s\n", rst_reg_name, opa_reg_name, opb_reg_name);
        emitInstruction(out, "sltu  $%s, $%s, 1\n", rst_reg_name, rst_reg_name);
        emitInstruction(out, "andi  $%s, $%s, 0x00ff\n", rst_reg_name, rst_reg_name);
        break;
    case OpNotEqual:
        emitInstruction(out, "xor   $%s, $%s, $%s\n", rst_reg_name, opa_reg_name, opb_reg_name);
        emitInstruction(out, "sltu  $%s, $0, $%s\n", rst_reg_name, rst_reg_name);
        emitInstruction(out, "andi  $%s, $%s, 0x00ff\n", rst_reg_name, rst_reg_name);
        break;
    case OpAdd:
        emitInstruction(out, "addu   $%s, $%s, $%s\n", rst_reg_name, opa_reg_name, opb_reg_name);
        break;
    case OpSubtract:
        emitInstruction(out, "subu   $%s, $%s, $%s\n", rst_reg_name, opa_reg_name, opb_reg_name);
        break;
    case OpMultiply:
        emitInstruction(out, "mult  $%s, $%s\n", opa_reg_name, opb_reg_name);
        emitInstruction(out, "mflo  $%s\n", rst_reg_name);
        break;
    case OpDivide:
        emitInstruction(out, "div   $0,$%s,$%s\n", opa_reg_name, opb_reg_name);
        emitInstruction(out, "mfhi  $%s\n", rst_reg_name);
        emitInstruction(out, "mflo  $%s\n", rst_reg_name);
        break;
    }
}

void fetchSourceLine(FILE* fp, int n, char* output, int maxLength)
{
    for (int i = 0; i < n && fgets(output, maxLength, fp); ++i)
        ; //printf("# %s", output);
}