src/org/xwt/mips/Compiler.java

   1 // Copyright 2003 Adam Megacz, see the COPYING file for licensing [GPL]
   2 package org.xwt.imp;
   3
   4 import java.util.*;
   5 import java.io.*;
   6
   7 // FIXME: lb/sb/sh/lh need not be word aligned
   8 // FIXME: memory accesses aren't handling sign-extending properly
   9 // FIXME: probably have to implement nonaligned access
  10 // FIXME: implement malloc()
  11
  12 // FIXME: implement an ELF parser based on RandomAccessFile
  13
  14 // FEATURE: progress indicator
  15 // FEATURE: support n32 abi (passes more arguments in registers)
  16 // FEATURE: trap on arithmetic overflows
  17 // FEATURE: FPU
  18 // FEATURE: we always know the value of the pc register; we should emit it as a literal when it appears in computations
  19 // FEATURE: emit bytecode rather than .java code (for on-the-fly classloading without javac present in "real" JVMs)
  20
  21 /** reads a fully linked MIPS ELF binary image on stdin; writes a .java file on stdout */
  22 public class MIPS {
  23
  24     static String runs = "";
  25     static int last_emit = -1;
  26     static DataInputStream dis;
  27     public static void main(String[] s) throws IOException {
  28
  29         if (s.length != 2) {
  30             System.err.println("usage: java " + MIPS.class.getName() + " <classname> <binary.mips>");
  31             System.exit(-1);
  32         }
  33
  34         String packageName = null;
  35         String className = s[0];
  36         if (s[0].indexOf('.') != -1) {
  37             packageName = s[0].substring(0, s[0].lastIndexOf('.'));
  38             className = s[0].substring(s[0].lastIndexOf('.') + 1);
  39         }
  40
  41         System.out.println(prefix + "// This file was generated by MipsToJava");
  42         if (packageName != null) System.out.println(prefix + "package " + packageName + ";");
  43         System.out.println(prefix + "public class " + className + " {");
  44         System.out.println(prefix + "");
  45         System.out.println(prefix + "    public " + className + "() { }");
  46         System.out.println(prefix + "");
  47         System.out.println(prefix + "    // memory");
  48         System.out.println(prefix + "    public int mem_read[][] = new int[65535][];");
  49         System.out.println(prefix + "");
  50         System.out.println(prefix + "    // same as mem_read unless a page is write-protected");
  51         System.out.println(prefix + "    public int mem_write[][] = new int[65535][];");
  52         System.out.println(prefix + "");
  53         System.out.println(prefix + "    // program counter");
  54         System.out.println(prefix + "    int pc = 0;");
  55         System.out.println(prefix + "");
  56         System.out.println(prefix + "    // temporary");
  57         System.out.println(prefix + "    int tmp = 0;");
  58         System.out.println(prefix + "");
  59         System.out.println(prefix + "    // MIPS multiply/divide subsystem; 64-bit result");
  60         System.out.println(prefix + "    long hilo = 0;");
  61         System.out.println(prefix + "");
  62         System.out.println(prefix + "    // General Purpose registers");
  63         System.out.println(prefix + "    final int r0 = 0;");
  64         System.out.println(prefix + "    int r1 = 0, r2 = 0, r3 = 0, r4 = 0, r5 = 0, r6 = 0, r7 = 0,");
  65         System.out.println(prefix + "        r8 = 0, r9 = 0, r10 = 0, r11 = 0, r12 = 0, r13 = 0, r14 = 0, r15 = 0,");
  66         System.out.println(prefix + "        r16 = 0, r17 = 0, r18 = 0, r19 = 0, r20 = 0, r21 = 0, r22 = 0, r23 = 0,");
  67         System.out.println(prefix + "        r24 = 0, r25 = 0, r26 = 0, r27 = 0, r28 = 0, r29 = 0, r30 = 0, r31 = 0;");
  68         System.out.println(prefix + "");
  69
  70         dis = new DataInputStream(new FileInputStream(s[1]));
  71
  72         // read the ELF header
  73         if (dis.readByte() != 0x7f || dis.readByte() != 'E' || dis.readByte() != 'L' || dis.readByte() != 'F')
  74             throw new RuntimeException("input file is not an ELF binary");
  75         dis.skip(12);
  76
  77         if (dis.readShort() != 2)
  78             throw new RuntimeException("binary is not a linked executable");
  79
  80         if (dis.readShort() != 8)
  81             throw new RuntimeException("binary is not a MIPS R3000 binary");
  82
  83         dis.skip(4);
  84
  85         int entry_point = dis.readInt();
  86         String entry_point_string = Long.toString(entry_point & 0xffffffffL, 16);
  87
  88         int ph_offset = dis.readInt();
  89         int sh_offset = dis.readInt();
  90         if (ph_offset == 0) throw new RuntimeException("binary is not statically linked");
  91         dis.skip(4);
  92         dis.skip(2);
  93
  94         int ph_entry_size = dis.readShort();
  95         int ph_num_entries = dis.readShort();
  96         int sh_entry_size = dis.readShort();
  97         int sh_num_entries = dis.readShort();
  98         int string_table_section_number = dis.readShort();
  99
 100         int skipamount = sh_offset - (4 + 12 + 2 + 2 + 4 + 4 + 4 + 4 + 4 + 2 + 2 + 2 + 2 + 2 + 2);
 101         while (skipamount>0) skipamount -= (int)dis.skip(skipamount);
 102
 103         int[] p_type = new int[sh_num_entries];
 104         int[] p_ofs = new int[sh_num_entries];
 105         int[] addr = new int[sh_num_entries];
 106         int[] p_size = new int[sh_num_entries];
 107         int[] p_name = new int[sh_num_entries];
 108         for(int i=0; i<sh_num_entries; i++) {
 109             p_name[i] = dis.readInt();
 110             p_type[i] = dis.readInt();
 111             dis.skip(4);
 112             addr[i] = dis.readInt();
 113             p_ofs[i] = dis.readInt();
 114             p_size[i] = dis.readInt();
 115             dis.skip(sh_entry_size - 4 * 6);
 116         }
 117
 118         dis.close();
 119         dis = new DataInputStream(new FileInputStream(s[1]));
 120
 121         int seek = p_ofs[string_table_section_number];
 122         while (seek > 0) seek -= dis.skip(seek);
 123         char[] stringTable = new char[p_size[string_table_section_number]];
 124         for(int i=0; i<p_size[string_table_section_number]; i++)
 125             stringTable[i] = (char)dis.readByte();
 126
 127         dis.close();
 128         dis = new DataInputStream(new FileInputStream(s[1]));
 129
 130         int pos = 0;
 131         for(int i=0; i<sh_num_entries; i++) {
 132
 133             String name = "";
 134             for(int j=p_name[i]; j<stringTable.length && stringTable[j] != 0; j++) name += stringTable[j];
 135             System.out.println();
 136             System.out.println(prefix + "// section \"" + name +
 137                                "\" #" + i + "; file offset 0x" + Long.toString(p_ofs[i] & 0xffffffffL, 16) +
 138                                ", vma 0x" + Long.toString(addr[i] & 0xffffffffL, 16) +
 139                                ", size 0x" + Long.toString(p_size[i] & 0xffffffff, 16));
 140
 141             if (name.equals(".sdata")) {
 142         if (last_emit != -1) {
 143             System.out.println(prefix + "                case 0x" + Long.toString((last_emit & 0xffffffffL) + 0x1000, 16) + ": return;");
 144             System.out.println(prefix + "                default: throw new Error(\"invalid address 0x\" + Long.toString(pc&0xffffffffL,16));");
 145             System.out.println(prefix + "        }");
 146             System.out.println(prefix + "    }");
 147             last_emit = -1;
 148         }
 149                 pos = 0; dis.close(); dis = new DataInputStream(new FileInputStream(s[1]));
 150                 while(pos < p_ofs[i]) pos += dis.skip(p_ofs[i] - pos);
 151                 String base = "0x" + Long.toString((addr[i] & 0xffff0000L) >> 16, 16);
 152                 System.out.println(prefix + "    private void initData() {");
 153                 System.out.println(prefix + "        r28 = 0x" + Long.toString((addr[i] - Short.MIN_VALUE - 12) & 0xffffffffL, 16) + ";");
 154                 System.out.println(prefix + "        mem_read[" + base + "] = mem_write[" + base + "] = new int[65535];");
 155                 for(long k=addr[i] & 0xffffffffL; k<((addr[i] + p_size[i]) & 0xffffffffL); k += 4)
 156                     System.out.println(prefix + "        mem_write[" + base + "][0x" + Long.toString(k & 0xffff, 16) + "] = 0x" +
 157                                        Long.toString(dis.readInt() & 0xffffffffL, 16) + ";");
 158                 System.out.println(prefix + "    }");
 159
 160             } else if (name.equals(".text") /*|| name.equals(".init")*/) {
 161                 if (pos > p_ofs[i]) { pos = 0; dis.close(); dis = new DataInputStream(new FileInputStream(s[1])); }
 162                 while(pos < p_ofs[i]) pos += dis.skip(p_ofs[i] - pos);
 163                 int remaining = p_size[i];
 164                 for(int ofs = addr[i]; ofs < addr[i] + p_size[i];) {
 165                     String base = Long.toString(ofs & 0xffffff00L, 16);
 166                     int len = Math.min(((ofs + 0x100) & 0xffffff00) - ofs, remaining);
 167                     emit(ofs, len, dis);
 168                     last_emit = ofs;
 169                     remaining -= len;
 170                     ofs += len;
 171                 }
 172             }
 173         }
 174
 175         if (last_emit != -1) {
 176             System.out.println(prefix + "                case 0x" + Long.toString((last_emit & 0xffffffffL) + 0x1000, 16) + ": return;");
 177             System.out.println(prefix + "                default: throw new Error(\"invalid address 0x\" + Long.toString(pc&0xffffffffL,16));");
 178             System.out.println(prefix + "        }");
 179             System.out.println(prefix + "    }");
 180             last_emit = -1;
 181         }
 182
 183         System.out.println();
 184         System.out.println(prefix + "    public static void main(String[] s) { new " + className + "().main(); }");
 185         System.out.println();
 186         System.out.println(prefix + "    public void main() {");
 187         System.out.println();
 188         System.out.println(prefix + "        // allocate the stack");
 189         System.out.println(prefix + "        mem_read[1] = mem_write[1] = new int[65535];");
 190         System.out.println();
 191         System.out.println(prefix + "        // set the stack pointer");
 192         System.out.println(prefix + "        r29 = 0x0001ff00;");
 193         System.out.println();
 194         System.out.println(prefix + "        // set the \"return address\" from _start to point at the \"magic exit address\" (0xdeadbeef)");
 195         System.out.println(prefix + "        r31 = 0xdeadbeef;");
 196         System.out.println();
 197         System.out.println(prefix + "        // read in the .data segment");
 198         System.out.println(prefix + "        initData();");
 199         System.out.println();
 200         System.out.println(prefix + "        trampoline(0x" + entry_point_string + ");");
 201         System.out.println();
 202         System.out.println(prefix + "    }");
 203
 204         System.out.println();
 205         System.out.println(prefix + "    public void trampoline(int pc) {");
 206         System.out.println(prefix + "        this.pc = pc;");
 207         System.out.println(prefix + "        while(true) {");
 208         System.out.println(prefix + "            switch(this.pc & 0xffffff00) {");
 209         System.out.println(prefix + "                case 0xdeadbe00: System.out.println(\"exiting with return value \" + r2); System.exit(r2); continue;");
 210         System.out.print(runs);
 211         System.out.println(prefix + "                default: throw new Error(\"invalid address 0x\" + Long.toString(this.pc&0xffffffffL,16));");
 212         System.out.println(prefix + "            }");
 213         System.out.println(prefix + "        }");
 214         System.out.println(prefix + "    }");
 215         System.out.println(prefix + "}");
 216     }
 217
 218     static int _instruction;
 219     static boolean readnext = true;
 220
 221     /** reads <tt>numbytes</tt> from the stream, emitting <tt>case</tt> blocks starting at vaddr <tt>ofs</tt> */
 222     static void emit(int vaddr, int numbytes, DataInputStream dis) throws IOException {
 223         if (last_emit != -1 && ((last_emit & 0xffffff00) != (vaddr & 0xffffff00))) {
 224             System.out.println(prefix + "                case 0x" + Long.toString((last_emit & 0xffffffffL) + 0x1000, 16) + ": return;");
 225             System.out.println(prefix + "                default: throw new Error(\"invalid address 0x\" + Long.toString(pc&0xffffffffL,16));");
 226             System.out.println(prefix + "        }");
 227             System.out.println(prefix + "    }");
 228         }
 229         if (last_emit == -1 || ((last_emit & 0xffffff00) != (vaddr & 0xffffff00))) {
 230             System.out.println("");
 231             System.out.println(prefix + "    private void run_" + Long.toString(vaddr & 0xffffff00L,16) + "() {");
 232             runs += "                case 0x" + Long.toString(vaddr & 0xffffff00L,16) +
 233                 ": run_" + Long.toString(vaddr & 0xffffff00L,16) + "(); continue;\n";
 234             System.out.println(prefix + "        switch(pc) {");
 235         }
 236         int ofs = vaddr;
 237         try {
 238             OUTER: for(ofs = vaddr; ofs < vaddr + numbytes; ofs+=4) {
 239                 if (readnext) _instruction = dis.readInt();
 240                 readnext = true;
 241
 242                 String istring = Long.toString(_instruction & 0xffffffffL, 16);
 243                 while(istring.length() < 8) istring = "0" + istring;
 244                 String ostring = Long.toString(ofs & 0xffffffffL, 16);
 245                 while(ostring.length() < 8) ostring = "0" + ostring;
 246                 System.out.print(prefix + "                /* " + istring + " */   case 0x" + ostring + ": System.out.println(\"pc=0x\" + Long.toString(pc&0xffffffffL,16));");
 247
 248                 emit_instruction(ofs, _instruction);
 249             }
 250         } catch (EOFException e) {
 251             emit(ofs, "                // warning, reached EOF before section end");
 252         } finally {
 253             last_emit = ofs;
 254         }
 255     }
 256
 257     private static void emit_instruction(int ofs, int instruction) throws IOException {
 258         int op = (instruction >>> 26) & 0xff;                // bits 26-31
 259         int rs = (instruction >> 21) & 0x1f;                 // bits 21-25
 260         int rt = (instruction >> 16) & 0x1f;                 // bits 16-20
 261         int rd = (instruction >> 11) & 0x1f;                 // bits 11-15
 262         int shamt = (instruction >> 6) & 0x1f;               // bits 6-10
 263         int subcode = instruction & 0x3f;                    // bits 0-5
 264
 265                 int branch_offset = (((instruction & 0x8000) << 16) | ((instruction & 0x7fff))) * 4;
 266                 int jump_target = (instruction & 0x03ffffff) * 4;
 267                 int signed_immediate = (int)((short)(instruction & 0xffff));
 268                 int unsigned_immediate = instruction & 0xffff;
 269
 270                 switch(op) {
 271
 272                     case 0: {
 273                         switch(subcode) {
 274
 275                         case 0:
 276                             if (instruction == 0) emit(ofs, "    /* NOP */;");                     // NOP
 277                             else emit(ofs, "    r" + rd + " = r" + rt + " << " + shamt + ";");     // SLL
 278                             break;
 279
 280                         case 1: throw new Error("opcode 0, subcode 1 is not part of the MIPS I instruction set");
 281
 282                         case 2:
 283                             emit(ofs, "    r" + rd + " = r" + rt + " >>> " + shamt + ";");    // SRL
 284                             break;
 285
 286                         case 3:
 287                             emit(ofs, "    r" + rd + " = r" + rt + " >> " + shamt + ";");     // SRA
 288                             break;
 289
 290                         case 4:
 291                             emit(ofs, "    r" + rd + " = r" + rt + " << (r" + rs + " % 32);");     // SLLV
 292                             break;
 293
 294                         case 5: throw new Error("opcode 0, subcode 5 is not part of the MIPS I instruction set");
 295
 296                         case 6:
 297                             emit(ofs, "    r" + rd + " = r" + rs + " >>> (r" + rt + " % 32);");     // SRLV
 298                             break;
 299
 300                         case 7:
 301                             emit(ofs, "    r" + rd + " = r" + rs + " >> (r" + rt + " % 32);");     // SRAV
 302                             break;
 303
 304                         case 8:
 305                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 306                             emit(ofs, "    pc = r" + rs + "; return;");                                   // JR
 307                             break;
 308
 309                         case 9:
 310                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 311                             emit(ofs, "    r" + rd + " = pc + 8; pc = r" + rs + "; return;");             // JALR
 312                             break;
 313
 314                         case 10: throw new Error("opcode 0, subcode 10 is not part of the MIPS I instruction set");
 315                         case 11: throw new Error("opcode 0, subcode 11 is not part of the MIPS I instruction set");
 316
 317                         case 12:
 318                             emit(ofs, "    syscall(" + ((instruction & 0x07ffffc0) >> 6) + ");");         // SYSCALL
 319                             break;
 320
 321                         case 13:
 322                             emit(ofs, "    /* BREAKPOINT */");
 323                             break;
 324
 325                         case 14: throw new Error("opcode 0, subcode 14 is not part of the MIPS I instruction set");
 326                         case 15: throw new Error("opcode 0, subcode 15 is not part of the MIPS I instruction set");
 327
 328                         case 16:
 329                             emit(ofs, "    r" + rd + " = (int)(hilo >>> 32);");               // MFHI
 330                             break;
 331
 332                         case 17:
 333                             emit(ofs, "    hilo = (hilo & 0x00000000ffffffffL) | ((r" + rs + " & 0xffffffffL) << 32);");   // MTHI
 334                             break;
 335
 336                         case 18:
 337                             emit(ofs, "    r" + rd + " = (int)hilo;");               // MFLO
 338                             break;
 339
 340                         case 19:
 341                             emit(ofs, "    hilo = (hilo & 0xffffffff00000000L) | (r" + rs + " & 0xffffffffL);");   // MTLO
 342                             break;
 343
 344                         case 20: throw new Error("opcode 0, subcode 20 is not part of the MIPS I instruction set");
 345                         case 22: throw new Error("opcode 0, subcode 22 is not part of the MIPS I instruction set");
 346                         case 23: throw new Error("opcode 0, subcode 23 is not part of the MIPS I instruction set");
 347
 348                         case 24:
 349                             emit(ofs, "    hilo = ((long)r" + rs + ") * ((long)r" + rt + ");");   // MULT
 350                             break;
 351
 352                         case 25:
 353                             emit(ofs, "    hilo = (r" + rs + " & 0xffffffffL) * (r" + rt + " & 0xffffffffL);");   // MULTU
 354                             break;
 355
 356                         case 26:
 357                             emit(ofs, "    hilo = (((r" + rs + " % r" + rt +") & 0xffffffffL) << 32) | ((r" + rs + " / r" + rt +") & 0xffffffffL);");   // DIV
 358                             break;
 359
 360                         case 27:
 361                             emit(ofs, "    hilo = (((r" + rs + " & 0xffffffffL) % (r" + rt +" & 0xffffffffL)) << 32) | " +               // DIVU
 362                                   "((r" + rs + " & 0xffffffffL) / (r" + rt +" & 0xffffffffL));");
 363                             break;
 364
 365                         case 28: throw new Error("opcode 0, subcode 28 is not part of the MIPS I instruction set");
 366                         case 29: throw new Error("opcode 0, subcode 29 is not part of the MIPS I instruction set");
 367                         case 30: throw new Error("opcode 0, subcode 30 is not part of the MIPS I instruction set");
 368                         case 31: throw new Error("opcode 0, subcode 31 is not part of the MIPS I instruction set");
 369
 370                         case 32:
 371                             emit(ofs, "    r" + rd + " = r" + rs + " + r" + rt + ";");                                                    // ADD
 372                             break;
 373
 374                         case 33:
 375                             emit(ofs, "    r" + rd + " = (int)(((r" + rs + " & 0xffffffffL) + (r" + rt + " & 0xffffffffL)));");           // ADDU
 376                             break;
 377
 378                         case 34:
 379                             emit(ofs, "    r" + rd + " = r" + rs + " - r" + rt + ";");                                                    // SUB
 380                             break;
 381
 382                         case 35:
 383                             emit(ofs, "    r" + rd + " = (int)(((r" + rs + " & 0xffffffffL) - (r" + rt + " & 0xffffffffL)));");           // SUBU
 384                             break;
 385
 386                         case 36:
 387                             emit(ofs, "    r" + rd + " = r" + rs + " & r" + rt + ";");                                                    // AND
 388                             break;
 389
 390                         case 37:
 391                             emit(ofs, "    r" + rd + " = r" + rs + " | r" + rt + ";");                                                    // OR
 392                             break;
 393
 394                         case 38:
 395                             emit(ofs, "    r" + rd + " = r" + rs + " ^ r" + rt + ";");                                                    // XOR
 396                             break;
 397
 398                         case 39:
 399                             emit(ofs, "    r" + rd + " = ~(r" + rs + " | r" + rt + ");");                                                 // NOR
 400                             break;
 401
 402                         case 40: throw new Error("opcode 0, subcode 40 is not part of the MIPS I instruction set");
 403                         case 41: throw new Error("opcode 0, subcode 41 is not part of the MIPS I instruction set");
 404
 405                         case 42:
 406                             emit(ofs, "    r" + rd + " = (r" + rs + " < r" + rt + ") ? 1 : 0;");                                          // SLT
 407                             break;
 408
 409                         case 43:
 410                             emit(ofs, "    r" + rd + " = ((r" + rs + " & 0xffffffffL) < (r" + rt + " & 0xffffffffL)) ? 1 : 0;");            // SLTU
 411                             break;
 412
 413                         case 44: case 45: case 46: case 47: case 48: case 49: case 50: case 51: case 52: case 53: case 54:
 414                         case 55: case 56: case 57: case 58: case 59: case 60: case 61: case 62: case 63:
 415                             throw new Error("opcode 0, subcode " + subcode + " is not part of the MIPS I instruction set");
 416                         default:
 417                             throw new Error("opcode 0, subcode " + subcode + " is not a valid MIPS instruction");
 418                         }
 419                         break;
 420                     }
 421
 422                 case 1: {
 423                     switch(rt) {
 424                     case 0:
 425                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 426                         emit(ofs, "    if (r" + rs + " < 0) { pc += " + (branch_offset + 4) + "; return; }; ");                            // BLTZ
 427                         break;
 428
 429                     case 1:
 430                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 431                         emit(ofs, "    if (r" + rs + " >= 0) { pc += " + (branch_offset + 4) + "; return; }; ");                               // BGEZ
 432                         break;
 433
 434                     case 16:
 435                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 436                         emit(ofs, "    r31 = pc + 4; if (r" + rs + " < 0) { pc += " + (branch_offset + 4) + "; return; }; ");                  // BLTZAL
 437                         break;
 438
 439                     case 17:
 440                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 441                         emit(ofs, "    r31 = pc + 4; if (r" + rs + " >= 0) { pc += " + (branch_offset + 4) + "; return; }; ");                // BGEZAL
 442                         break;
 443
 444                     default: throw new Error("opcode 1, subcode " + rt + " is not part of the MIPS I instruction set");
 445                     }
 446                     break;
 447                 }
 448
 449                 case 2:
 450                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 451                     emit(ofs, "    pc &= 0xf0000000; pc |= 0x" + Long.toString(jump_target & 0xffffffffL, 16) + "; return;");                                            // J
 452                     break;
 453
 454                 case 3:
 455                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 456                     emit(ofs, "    r31 = pc + 4; pc &= 0xf0000000; pc |= 0x" + Long.toString(jump_target & 0xffffffffL, 16) + "; return;");                                  // JAL
 457                     break;
 458
 459                 case 4:
 460                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 461                     emit(ofs, "    if (r" + rs + " == r" + rt + ") { pc += 0x" + Long.toString((branch_offset + 4) & 0xffffffffL, 16) + "; return; }; ");                  // BEQ
 462                     break;
 463
 464                 case 5:
 465                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 466                     emit(ofs, "    if (r" + rs + " != r" + rt + ") { pc += 0x" + Long.toString((branch_offset + 4) & 0xffffffffL, 16) + "; return; }; ");                  // BNE
 467                     break;
 468
 469                 case 6:
 470                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 471                     emit(ofs, "    if (r" + rs + " <= 0) { pc += 0x" + Long.toString((branch_offset + 4) & 0xffffffffL, 16) + "; return; }; ");                            // BLEZ
 472                     break;
 473
 474                 case 7:
 475                             _instruction = dis.readInt(); readnext = false; emit_instruction(ofs, _instruction);
 476                     emit(ofs, "    if (r" + rs + " > 0) { pc += 0x" + Long.toString((branch_offset + 4) & 0xffffffffL, 16) + "; return; }; ");                             // BGTZ
 477                     break;
 478
 479                 case 8: case 9:
 480                     emit(ofs, "    r" + rt + " = r" + rs + " + " + signed_immediate + ";");                                         // ADDI[U]
 481                     break;
 482
 483                 case 10:
 484                     emit(ofs, "    r" + rt + " = (r" + rs + " < " + signed_immediate + ") ? 1 : 0;");                               // SLTI
 485                     break;
 486
 487                 case 11:
 488                     emit(ofs, "    r" + rt + " = ((r" + rs + " & 0xffffffffL) < (" + signed_immediate + " & 0xffffffffL)) ? 1 : 0;");     // SLTIU
 489                     break;
 490
 491                 case 12:
 492                     emit(ofs, "    r" + rt + " = r" + rs + " & " + unsigned_immediate + ";");                                         // ANDI
 493                     break;
 494
 495                 case 13:
 496                     emit(ofs, "    r" + rt + " = r" + rs + " | " + unsigned_immediate + ";");                                         // ORI
 497                     break;
 498
 499                 case 14:
 500                     emit(ofs, "    r" + rt + " = r" + rs + " ^ " + unsigned_immediate + ";");                                         // XORI
 501                     break;
 502
 503                 case 15:
 504                     emit(ofs, "    r" + rt + " = " + unsigned_immediate + " << 16;");                                                 // LUI
 505                     break;
 506
 507                 case 16: /* throw new Error("coprocessor instructions (opcode 16) are not implemented"); */
 508                     emit(ofs, "    throw new Error(\"coprocessor instructions (opcode 16) are not implemented\");");
 509                     break;
 510                 case 17: throw new Error("coprocessor instructions (opcode 17) are not implemented");
 511                 case 18: throw new Error("coprocessor instructions (opcode 18) are not implemented");
 512
 513                 case 19: case 20: case 21: case 22: case 23: case 24: case 25: case 26: case 27: case 28:
 514                     throw new Error("opcode " + op + " is not part of the MIPS I instruction set @" + Long.toString(ofs & 0xffffffffL, 16));
 515
 516                 case 32: {
 517                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 518                     emit(ofs, "    tmp = mem_read[" + dest + ">>>16][" + dest + " & 0xffff];  r" + rt + " = ((tmp & 0x80) << 24) | (tmp & 0x7f);");       // LB
 519                     break;
 520                 }
 521
 522                 case 33:  {
 523                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 524                     emit(ofs, "    tmp = mem_read[" + dest + ">>>16][" + dest + " & 0xffff];  r" + rt + " = ((tmp & 0x8000) << 16) | (tmp & 0x7fff);");   // LH
 525                     break;
 526                 }
 527
 528                 case 34:
 529                     emit(ofs, "    throw new Error(\"LWL (opcode 34) is not supported; are you sure you used -mstrict-align?\");");
 530                     break;
 531
 532                 case 35: {
 533                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 534                     emit(ofs, "    r" + rt + " = mem_read[" + dest + ">>>16][" + dest + " & 0xffff];");               // LW
 535                     break;
 536                 }
 537
 538                 case 36: {
 539                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 540                     emit(ofs, "    r" + rt + " = mem_read[" + dest + ">>>16][" + dest + " & 0xffff] & 0xff;");       // LBU
 541                     break;
 542                 }
 543
 544                 case 37: {
 545                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 546                     emit(ofs, "    r" + rt + " = mem_read[" + dest + ">>>16][" + dest + " & 0xffff] & 0xffff;");       // LHU
 547                     break;
 548                 }
 549
 550                 case 38:
 551                     emit(ofs, "    throw new Error(\"LWR (opcode 38) is not supported; are you sure you used -mstrict-align?\");");
 552                     break;
 553
 554                 case 39:  throw new Error("opcode 39 is not part of the MIPS I instruction set");
 555
 556                 case 40: {
 557                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 558                     emit(ofs, "    tmp = mem_read[" + dest + ">>>16][" + dest + " & 0xffff]; " +
 559                           "mem_write[" + dest + ">>>16][" + dest + " & 0xffff] = (tmp & 0xffffff00) | (r" + rt + " & 0xff);");   // SB
 560                     break;
 561                 }
 562
 563                 case 41: {
 564                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 565                     emit(ofs, "    tmp = mem_read[" + dest + ">>>16][" + dest + " & 0xffff]; " +
 566                           "mem_write[" + dest + ">>>16][" + dest + " & 0xffff] = (tmp & 0xffff0000) | (r" + rt + " & 0xffff);");   // SH
 567                     break;
 568                 }
 569
 570                 case 42:
 571                     emit(ofs, "    throw new Error(\"SWL (opcode 42) is not supported; are you sure you used -mstrict-align?\");");
 572                     break;
 573
 574                 case 43: {
 575                     String dest = "(r" + rs + " + " + signed_immediate + ")";
 576                     emit(ofs, "    mem_write[" + dest + ">>>16][" + dest + " & 0xffff] = r" + rt + ";");               // SW
 577                     break;
 578                 }
 579
 580                 case 44:  throw new Error("opcode 44 is not part of the MIPS I instruction set");
 581                 case 45:  throw new Error("opcode 45 is not part of the MIPS I instruction set");
 582
 583                 case 46:
 584                     emit(ofs, "    throw new Error(\"SWR (opcode 46) is not supported; are you sure you used -mstrict-align?\");");
 585                     break;
 586
 587                 case 47:  throw new Error("opcode 47 is not part of the MIPS I instruction set");
 588                 case 48:  throw new Error("opcode 48 is not part of the MIPS I instruction set");
 589
 590                 case 49:
 591                     emit(ofs, "    throw new Error(\"floating point operations (opcode 49) are not yet supported\");");
 592                     break;
 593
 594                 case 50:
 595                     emit(ofs, "    throw new Error(\"floating point operations (opcode 50) are not yet supported\");");
 596                     break;
 597
 598                 case 51: case 52: case 53: case 54: case 55: case 56:
 599                     throw new Error("opcode " + op + " is not part of the MIPS I instruction set");
 600
 601                 case 57:
 602                     emit(ofs, "    throw new Error(\"floating point operations (opcode 57) are not yet supported\");");
 603                     break;
 604
 605                 case 58:
 606                     emit(ofs, "    throw new Error(\"floating point operations (opcode 58) are not yet supported\");");
 607                     break;
 608
 609                 case 60: case 61: case 62: case 63:
 610                     throw new Error("opcode " + op + " is not part of the MIPS I instruction set");
 611
 612                 default:
 613                     throw new Error("unknown opcode " + op);
 614                 }
 615     }
 616
 617
 618
 619     static String prefix = "";
 620     static void emit(int vaddr, String s) {
 621         if (s.indexOf("r0 = ") != -1) s = "    /* NOP */";
 622         if (!s.trim().endsWith("return;") && s.indexOf("throw") == -1) s += " pc = 0x" + Long.toString((vaddr + 4) & 0xffffffffL,16) + ";";
 623         System.out.println(s);
 624     }
 625 }
 626