1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 2 3 <html> 4 5 <head> 6 <title>Dalvik VM Instruction Formats</title> 7 <link rel=stylesheet href="instruction-formats.css"> 8 </head> 9 10 <body> 11 12 <h1>Dalvik VM Instruction Formats</h1> 13 <p>Copyright © 2007 The Android Open Source Project 14 15 <h2>Introduction and Overview</h2> 16 17 <p>This document lists the instruction formats used by Dalvik bytecode 18 and is meant to be used in conjunction with the 19 <a href="dalvik-bytecode.html">bytecode reference document</a>.</p> 20 21 <h3>Bitwise descriptions</h3> 22 23 <p>The first column in the format table lists the bitwise layout of 24 the format. It consists of one or more space-separated "words" each of 25 which describes a 16-bit code unit. Each character in a word 26 represents four bits, read from high bits to low, with vertical bars 27 ("<code>|</code>") interspersed to aid in reading. Uppercase letters 28 in sequence from "<code>A</code>" are used to indicate fields within 29 the format (which then get defined further by the syntax column). The term 30 "<code>op</code>" is used to indicate the position of the eight-bit 31 opcode within the format. A slashed zero ("<code>Ø</code>") is 32 used to indicate that all bits should be zero in the indicated 33 position.</p> 34 35 <p>For example, the format "<code>B|A|<i>op</i> CCCC</code>" indicates 36 that the format consists of two 16-bit code units. The first word 37 consists of the opcode in the low eight bits and a pair of four-bit 38 values in the high eight bits; and the second word consists of a single 39 16-bit value.</p> 40 41 <h3>Format IDs</h3> 42 43 <p>The second column in the format table indicates the short identifier 44 for the format, which is used in other documents and in code to identify 45 the format.</p> 46 47 <p>Format IDs consist of three characters, two digits followed by a 48 letter. The first digit indicates the number of 16-bit code units in the 49 format. The second digit indicates the maximum number of registers that the 50 format contains (maximum, since some formats can accomodate a variable 51 number of registers), with the special designation "<code>r</code>" indicating 52 that a range of registers is encoded. The final letter semi-mnemonically 53 indicates the type of any extra data encoded by the format. For example, 54 format "<code>21t</code>" is of length two, contains one register reference, 55 and additionally contains a branch target.</p> 56 57 <p>Suggested static linking formats have an additional "<code>s</code>" suffix, 58 making them four characters total.</p> 59 60 <p>The full list of typecode letters are as follows. Note that some 61 forms have different sizes, depending on the format:</p> 62 63 <table class="letters"> 64 <thead> 65 <tr> 66 <th>Mnemonic</th> 67 <th>Bit Sizes</th> 68 <th>Meaning</th> 69 </tr> 70 </thead> 71 <tbody> 72 <tr> 73 <td>b</td> 74 <td>8</td> 75 <td>immediate signed <b>b</b>yte</td> 76 </tr> 77 <tr> 78 <td>c</td> 79 <td>16, 32</td> 80 <td><b>c</b>onstant pool index</td> 81 </tr> 82 <tr> 83 <td>f</td> 84 <td>16</td> 85 <td>inter<b>f</b>ace constants (only used in statically linked formats) 86 </td> 87 </tr> 88 <tr> 89 <td>h</td> 90 <td>16</td> 91 <td>immediate signed <b>h</b>at (high-order bits of a 32- or 64-bit 92 value; low-order bits are all <code>0</code>) 93 </td> 94 </tr> 95 <tr> 96 <td>i</td> 97 <td>32</td> 98 <td>immediate signed <b>i</b>nt, or 32-bit float</td> 99 </tr> 100 <tr> 101 <td>l</td> 102 <td>64</td> 103 <td>immediate signed <b>l</b>ong, or 64-bit double</td> 104 </tr> 105 <tr> 106 <td>m</td> 107 <td>16</td> 108 <td><b>m</b>ethod constants (only used in statically linked formats)</td> 109 </tr> 110 <tr> 111 <td>n</td> 112 <td>4</td> 113 <td>immediate signed <b>n</b>ibble</td> 114 </tr> 115 <tr> 116 <td>s</td> 117 <td>16</td> 118 <td>immediate signed <b>s</b>hort</td> 119 </tr> 120 <tr> 121 <td>t</td> 122 <td>8, 16, 32</td> 123 <td>branch <b>t</b>arget</td> 124 </tr> 125 <tr> 126 <td>x</td> 127 <td>0</td> 128 <td>no additional data</td> 129 </tr> 130 </tbody> 131 </table> 132 133 <h3>Syntax</h3> 134 135 <p>The third column of the format table indicates the human-oriented 136 syntax for instructions which use the indicated format. Each instruction 137 starts with the named opcode and is optionally followed by one or 138 more arguments, themselves separated with commas.</p> 139 140 <p>Wherever an argument refers to a field from the first column, the 141 letter for that field is indicated in the syntax, repeated once for 142 each four bits of the field. For example, an eight-bit field labeled 143 "<code>BB</code>" in the first column would also be labeled 144 "<code>BB</code>" in the syntax column.</p> 145 146 <p>Arguments which name a register have the form "<code>v<i>X</i></code>". 147 The prefix "<code>v</code>" was chosen instead of the more common 148 "<code>r</code>" exactly to avoid conflicting with (non-virtual) architectures 149 on which a Dalvik virtual machine might be implemented which themselves 150 use the prefix "<code>r</code>" for their registers. (That is, this 151 decision makes it possible to talk about both virtual and real registers 152 together without the need for circumlocution.)</p> 153 154 <p>Arguments which indicate a literal value have the form 155 "<code>#+<i>X</i></code>". Some formats indicate literals that only 156 have non-zero bits in their high-order bits; for these, the zeroes 157 are represented explicitly in the syntax, even though they do not 158 appear in the bitwise representation.</p> 159 160 <p>Arguments which indicate a relative instruction address offset have the 161 form "<code>+<i>X</i></code>".</p> 162 163 <p>Arguments which indicate a literal constant pool index have the form 164 "<code><i>kind</i>@<i>X</i></code>", where "<code><i>kind</i></code>" 165 indicates which constant pool is being referred to. Each opcode that 166 uses such a format explicitly allows only one kind of constant; see 167 the opcode reference to figure out the correspondence. The four 168 kinds of constant pool are "<code>string</code>" (string pool index), 169 "<code>type</code>" (type pool index), "<code>field</code>" (field 170 pool index), and "<code>meth</code>" (method pool index).</p> 171 172 <p>Similar to the representation of constant pool indices, there are 173 also suggested (optional) forms that indicate prelinked offsets or 174 indices. These prelinked values include "<code>vtaboff</code>" 175 (vtable offset), "<code>fieldoff</code>" (field offset), and 176 "<code>iface</code>" (interface pool index).</p> 177 178 <p>In the cases where a format value isn't explictly part of the syntax 179 but instead picks a variant, each variant is listed with the prefix 180 "<code>[<i>X</i>=<i>N</i>]</code>" (e.g., "<code>[B=2]</code>") to indicate 181 the correspondence.</p> 182 183 <h2>The Formats</h2> 184 185 <table class="format"> 186 <thead> 187 <tr> 188 <th>Format</th> 189 <th>ID</th> 190 <th>Syntax</th> 191 <th>Notable Opcodes Covered</th> 192 </tr> 193 </thead> 194 <tbody> 195 <tr> 196 <td>ØØ|<i>op</i></td> 197 <td>10x</td> 198 <td><i><code>op</code></i></td> 199 <td> </td> 200 </tr> 201 <tr> 202 <td rowspan="2">B|A|<i>op</i></td> 203 <td>12x</td> 204 <td><i><code>op</code></i> vA, vB</td> 205 <td> </td> 206 </tr> 207 <tr> 208 <td>11n</td> 209 <td><i><code>op</code></i> vA, #+B</td> 210 <td> </td> 211 </tr> 212 <tr> 213 <td rowspan="2">AA|<i>op</i></td> 214 <td>11x</td> 215 <td><i><code>op</code></i> vAA</td> 216 <td> </td> 217 </tr> 218 <tr> 219 <td>10t</td> 220 <td><i><code>op</code></i> +AA</td> 221 <td>goto</td> 222 </tr> 223 <tr> 224 <td>ØØ|<i>op</i> AAAA</td></td> 225 <td>20t</td> 226 <td><i><code>op</code></i> +AAAA</td> 227 <td>goto/16</td> 228 </tr> 229 <tr> 230 <td rowspan="5">AA|<i>op</i> BBBB</td> 231 <td>22x</td> 232 <td><i><code>op</code></i> vAA, vBBBB</td> 233 <td> </td> 234 </tr> 235 <tr> 236 <td>21t</td> 237 <td><i><code>op</code></i> vAA, +BBBB</td> 238 <td> </td> 239 </tr> 240 <tr> 241 <td>21s</td> 242 <td><i><code>op</code></i> vAA, #+BBBB</td> 243 <td> </td> 244 </tr> 245 <tr> 246 <td>21h</td> 247 <td><i><code>op</code></i> vAA, #+BBBB0000<br/> 248 <i><code>op</code></i> vAA, #+BBBB000000000000 249 </td> 250 <td> </td> 251 </tr> 252 <tr> 253 <td>21c</td> 254 <td><i><code>op</code></i> vAA, type@BBBB<br/> 255 <i><code>op</code></i> vAA, field@BBBB<br/> 256 <i><code>op</code></i> vAA, string@BBBB 257 </td> 258 <td>check-cast<br/> 259 const-class<br/> 260 const-string 261 </td> 262 </tr> 263 <tr> 264 <td rowspan="2">AA|<i>op</i> CC|BB</td> 265 <td>23x</td> 266 <td><i><code>op</code></i> vAA, vBB, vCC</td> 267 <td> </td> 268 </tr> 269 <tr> 270 <td>22b</td> 271 <td><i><code>op</code></i> vAA, vBB, #+CC</td> 272 <td> </td> 273 </tr> 274 <tr> 275 <td rowspan="4">B|A|<i>op</i> CCCC</td> 276 <td>22t</td> 277 <td><i><code>op</code></i> vA, vB, +CCCC</td> 278 <td> </td> 279 </tr> 280 <tr> 281 <td>22s</td> 282 <td><i><code>op</code></i> vA, vB, #+CCCC</td> 283 <td> </td> 284 </tr> 285 <tr> 286 <td>22c</td> 287 <td><i><code>op</code></i> vA, vB, type@CCCC<br/> 288 <i><code>op</code></i> vA, vB, field@CCCC 289 </td> 290 <td>instance-of</td> 291 </tr> 292 <tr> 293 <td>22cs</td> 294 <td><i><code>op</code></i> vA, vB, fieldoff@CCCC</td> 295 <td><i>(suggested format for statically linked field access instructions of 296 format 22c)</i> 297 </td> 298 </tr> 299 <tr> 300 <td>ØØ|<i>op</i> AAAA<sub>lo</sub> AAAA<sub>hi</sub></td></td> 301 <td>30t</td> 302 <td><i><code>op</code></i> +AAAAAAAA</td> 303 <td>goto/32</td> 304 </tr> 305 <tr> 306 <td>ØØ|<i>op</i> AAAA BBBB</td> 307 <td>32x</td> 308 <td><i><code>op</code></i> vAAAA, vBBBB</td> 309 <td> </td> 310 </tr> 311 <tr> 312 <td rowspan="3">AA|<i>op</i> BBBB<sub>lo</sub> BBBB<sub>hi</sub></td> 313 <td>31i</td> 314 <td><i><code>op</code></i> vAA, #+BBBBBBBB</td> 315 <td> </td> 316 </tr> 317 <tr> 318 <td>31t</td> 319 <td><i><code>op</code></i> vAA, +BBBBBBBB</td> 320 <td> </td> 321 </tr> 322 <tr> 323 <td>31c</td> 324 <td><i><code>op</code></i> vAA, string@BBBBBBBB</td> 325 <td>const-string/jumbo</td> 326 </tr> 327 <tr> 328 <td>B|A|<i>op</i> CCCC G|F|E|D</td> 329 <td>35c</td> 330 <td><i>[<code>B=5</code>] <code>op</code></i> {vD, vE, vF, vG, vA}, 331 meth@CCCC<br/> 332 <i>[<code>B=5</code>] <code>op</code></i> {vD, vE, vF, vG, vA}, 333 type@CCCC<br/> 334 <i>[<code>B=4</code>] <code>op</code></i> {vD, vE, vF, vG}, 335 <i><code>kind</code></i>@CCCC<br/> 336 <i>[<code>B=3</code>] <code>op</code></i> {vD, vE, vF}, 337 <i><code>kind</code></i>@CCCC<br/> 338 <i>[<code>B=2</code>] <code>op</code></i> {vD, vE}, 339 <i><code>kind</code></i>@CCCC<br/> 340 <i>[<code>B=1</code>] <code>op</code></i> {vD}, 341 <i><code>kind</code></i>@CCCC<br/> 342 <i>[<code>B=0</code>] <code>op</code></i> {}, 343 <i><code>kind</code></i>@CCCC 344 </td> 345 <td> </td> 346 </tr> 347 <tr> 348 <td>B|A|<i>op</i> CCCC G|F|E|D</td> 349 <td>35ms</td> 350 351 <td><i>[<code>B=5</code>] <code>op</code></i> {vD, vE, vF, vG, vA}, 352 vtaboff@CCCC<br/> 353 <i>[<code>B=4</code>] <code>op</code></i> {vD, vE, vF, vG}, 354 vtaboff@CCCC<br/> 355 <i>[<code>B=3</code>] <code>op</code></i> {vD, vE, vF}, 356 vtaboff@CCCC<br/> 357 <i>[<code>B=2</code>] <code>op</code></i> {vD, vE}, 358 vtaboff@CCCC<br/> 359 <i>[<code>B=1</code>] <code>op</code></i> {vD}, 360 vtaboff@CCCC<br/> 361 </td> 362 <td><i>(suggested format for statically linked <code>invoke-virtual</code> 363 and <code>invoke-super</code> instructions of format 35c)</i> 364 </td> 365 </tr> 366 <tr> 367 <td>B|A|<i>op</i> DDCC H|G|F|E</td> 368 <td>35fs</td> 369 <td><i>[<code>B=5</code>] <code>op</code></i> {vE, vF, vG, vH, vA}, 370 vtaboff@CC, iface@DD<br/> 371 <i>[<code>B=4</code>] <code>op</code></i> {vE, vF, vG, vH}, 372 vtaboff@CC, iface@DD<br/> 373 <i>[<code>B=3</code>] <code>op</code></i> {vE, vF, vG}, 374 vtaboff@CC, iface@DD<br/> 375 <i>[<code>B=2</code>] <code>op</code></i> {vE, vF}, 376 vtaboff@CC, iface@DD<br/> 377 <i>[<code>B=1</code>] <code>op</code></i> {vE}, 378 vtaboff@CC, iface@DD<br/> 379 </td> 380 <td><i>(suggested format for statically linked <code>invoke-interface</code> 381 instructions of format 35c)</i> 382 </td> 383 </tr> 384 <tr> 385 <td>AA|<i>op</i> BBBB CCCC</td> 386 <td>3rc</td> 387 <td><i><code>op</code></i> {vCCCC .. vNNNN}, meth@BBBB<br/> 388 <i><code>op</code></i> {vCCCC .. vNNNN}, type@BBBB<br/> 389 <p><i>(where <code>NNNN = CCCC+AA-1</code>, that is <code>A</code> 390 determines the count <code>0..255</code>, and <code>C</code> 391 determines the first register)</i></p> 392 </td> 393 <td> </td> 394 </tr> 395 <tr> 396 <td>AA|<i>op</i> BBBB CCCC</td> 397 <td>3rms</td> 398 <td><i><code>op</code></i> {vCCCC .. vNNNN}, vtaboff@BBBB<br/> 399 <p><i>(where <code>NNNN = CCCC+AA-1</code>, that is <code>A</code> 400 determines the count <code>0..255</code>, and <code>C</code> 401 determines the first register)</i></p> 402 </td> 403 <td><i>(suggested format for statically linked <code>invoke-virtual</code> 404 and <code>invoke-super</code> instructions of format <code>3rc</code>)</i> 405 </td> 406 </tr> 407 <tr> 408 <td>AA|<i>op</i> CCBB DDDD</td> 409 <td>3rfs</td> 410 <td><i><code>op</code></i> {vDDDD .. vNNNN}, vtaboff@BB, 411 iface@CC<br/> 412 <p><i>(where <code>NNNN = DDDD+AA-1</code>, that is <code>A</code> 413 determines the count <code>0..255</code>, and <code>D</code> 414 determines the first register)</i></p> 415 </td> 416 <td><i>(suggested format for statically linked <code>invoke-interface</code> 417 instructions of format <code>3rc</code>)</i> 418 </td> 419 </tr> 420 <tr> 421 <td>AA|<i>op</i> BBBB<sub>lo</sub> BBBB BBBB BBBB<sub>hi</sub></td> 422 <td>51l</td> 423 <td><i><code>op</code></i> vAA, #+BBBBBBBBBBBBBBBB</td> 424 <td>const-wide</td> 425 </tr> 426 </tbody> 427 </table> 428 429 </body> 430 </html> 431
