简单MIPS汇编器
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OTL终于能写出点实用的东西了。今天写的一个MIPS汇编器，能读入若干行MIPS指令，将其翻译成机器码，存入一个文本文件中。目前只能编译add, sub, and, or, slt, beq, j, lw, sw, nop这几种指令，并且不能识别注释。不过对于完成计算机组成实验来说足够了。
// A simple and naive MIPS assembler// Use this command to make: g++ MIPS.cpp -o MIPS// Usage: ./MIPS CodeFile#include<iostream>#include<stdio.h>#include<memory.h>#include<cstring>#include<fstream>#include<iomanip>#include<cstdlib>using namespace std;// A function used to extract the register number from string "$xx"int getReg(char* arg){ int reg = 0; char *p = arg; while (*p == ' ') p++; // Skip the space at the beginning if (*p == '$') p++; else return -1; // Unexpected charaters // Parse while(*p >= '0' && *p <= '9'){ reg = 10 * reg + (*p - '0'); p++; } while (*p == ' ') p++; // Skip the space following the number if (*p != '\0') return -1; // Unexpected characters else return reg;}// Output a binary number with a given length to an object of ostreamvoid printBin(int num, int digi, ostream& os){ char *bin = new char[digi]; memset(bin, '0', digi * sizeof(char)); char *p = bin + (strlen(bin) - 1); int sign = (num >= 0)? 1: -1; num = num * sign; while (num > 0){ if (num & 1) *p = '1'; num >>= 1; p--; } // Transform to the 2's complement if (sign == -1){ p = bin + (strlen(bin) - 1); while (p >= bin && *p != '1') p--; // Find the last '1' if (p >= bin && *p == '1') p--; // Skip the last '1' while (p >= bin) { *p = ('0' + '1') - *p; p--; } } os << bin; delete bin;} int main(int argc, char** argv){ // Check the input if (argc != 2){ cout << "Error: File name needed." << endl; exit(-1); } ifstream code(argv[1]); char *objname = new char[strlen(argv[1]) + 10]; strcpy(objname, argv[1]); int i; // Find the suffix for (i = strlen(objname) - 1; i >= 0; i--) if (objname[i] == '.') break; // Give the output file a ".mips" suffix if (objname[i] == '.'){ objname[i + 1] = '\0'; strcat(objname, "mips"); } else strcat(objname, ".mips"); ofstream obj(objname); delete objname; /**************************************************** The instruction strctures R-type: +------------------------------------------------+ | opcode | rs | rt | rd | shamt | funct | |--------+-------+-------+-------+-------+-------| | 6-bit | 5-bit | 5-bit | 5-bit | 5-bit | 6-bit | +------------------------------------------------+ I-type: +------------------------------------------------+ | opcode | rs | rt | immediate | |--------+-------+-------+-----------------------| | 6-bit | 5-bit | 5-bit | 16-bit | +------------------------------------------------+ J-type: +------------------------------------------------+ | opcode | jump address | |--------+---------------------------------------| | 6-bit | 26-bit | +------------------------------------------------+ */ char command[20], arg1[20], arg2[20], arg3[20]; int line_no = 0; while (code >> command){ line_no++; // The current line //code >> command; if (!strcmp(command, "add")){ // ADD $rd, $rs, $rt printBin(0, 6, obj); // OpCode //code >> arg1 >> arg2 >> arg3; code.getline(arg1, 20, ','); int rd = getReg(arg1); if (rd == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20, ','); int rs = getReg(arg2); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg3, 20); int rt = getReg(arg3); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(rd, 5, obj); printBin(0, 5, obj); // shamt printBin(0x20, 6, obj); // funct obj << endl; } else if (!strcmp(command, "sub")){ // SUB $rd, $rs, $rt printBin(0, 6, obj); // OpCode code.getline(arg1, 20, ','); int rd = getReg(arg1); if (rd == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20, ','); int rs = getReg(arg2); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg3, 20); int rt = getReg(arg3); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(rd, 5, obj); printBin(0, 5, obj); // shamt printBin(0x22, 6, obj); // funct obj << endl; } else if (!strcmp(command, "and")){ // AND $rd, $rs, $rt printBin(0, 6, obj); // OpCode code.getline(arg1, 20, ','); int rd = getReg(arg1); if (rd == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20, ','); int rs = getReg(arg2); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg3, 20); int rt = getReg(arg3); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(rd, 5, obj); printBin(0, 5, obj); // shamt printBin(0x24, 6, obj); // funct obj << endl; } else if (!strcmp(command, "or")){// OR $rd, $rs, $rt printBin(0, 6, obj); // OpCode code.getline(arg1, 20, ','); int rd = getReg(arg1); if (rd == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20, ','); int rs = getReg(arg2); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg3, 20); int rt = getReg(arg3); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(rd, 5, obj); printBin(0, 5, obj); // shamt printBin(0x25, 6, obj); // funct obj << endl; } else if (!strcmp(command, "slt")){// SLT $rd, $rs, $rt printBin(0, 6, obj); // OpCode code.getline(arg1, 20, ','); int rd = getReg(arg1); if (rd == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20, ','); int rs = getReg(arg2); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg3, 20); int rt = getReg(arg3); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(rd, 5, obj); printBin(0, 5, obj); // shamt printBin(0x2A, 6, obj); // funct obj << endl; } else if (!strcmp(command, "beq")){ // BEQ $rs, $rt, imm printBin(0x4, 6, obj); // OpCode code.getline(arg1, 20, ','); int rs = getReg(arg1); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20, ','); int rt = getReg(arg2); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } int offset; code >> offset; printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(offset, 16, obj); // immediate obj << endl; } else if (!strcmp(command, "lw")){ // LW $rt, offset($rs) printBin(0x23, 6, obj); // OpCode code.getline(arg1, 20, ','); int rt = getReg(arg1); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20); int offset = 0; int sign = 1; char *p = arg2; while (*p == ' ') p++; if (*p == '-'){ p++; sign = -1; } // Parse while (*p >= '0' && *p <= '9'){ offset = 10 * offset + (*p - '0'); p++; } offset = sign * offset; while (*p == ' ') p++; // Skip the space before '(' if (*p == '(') p++; else { cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } char *q = arg2 + (strlen(arg2) - 1); while (*q == ' ') q--; if (*q == ')') *q = '\0'; // Find the ')' and delete it else { // No ')' found, syntax error occurred cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } int rs = getReg(p); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(offset, 16, obj); obj << endl; } else if (!strcmp(command, "sw")){ // SW $rt, offset($rs) printBin(0x2B, 6, obj); // OpCode code.getline(arg1, 20, ','); int rt = getReg(arg1); if (rt == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } code.getline(arg2, 20); int offset = 0; int sign = 1; char *p = arg2; while (*p == ' ') p++; if (*p == '-'){ p++; sign = -1; } // Parse while (*p >= '0' && *p <= '9'){ offset = 10 * offset + (*p - '0'); p++; } offset = sign * offset; while (*p == ' ') p++; // Skip the space before '(' if (*p == '(') p++; else { cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } char *q = arg2 + (strlen(arg2) - 1); while (*q == ' ') q--; if (*q == ')') *q = '\0'; // Find the ')' and delete it else { // No ')' found, syntax error occurred cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } int rs = getReg(p); if (rs == -1){ cout << "Syntax error at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(rs, 5, obj); printBin(rt, 5, obj); printBin(offset, 16, obj); obj << endl; } else if (!strcmp(command, "j")){ // J addr printBin(0x02, 6, obj); // OpCode int addr; code >> addr; if (addr < 0){ // Negative address is not allowed cout << "Invalid address at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } printBin(addr, 26, obj); obj << endl; } else if (!strcmp(command, "nop")){ // NOP printBin(0, 32, obj); obj << endl; } else { // No other instructions allowed cout << "Invalid instruction at Line " << line_no << "." << endl; code.close(); obj.close(); exit(-1); } } code.close(); obj.close(); return 0;} 0 0
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