| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 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>instance-of</title> |
| 7 | <link rel=stylesheet href="opcode.css"> |
| 8 | </head> |
| 9 | |
| 10 | <body> |
| 11 | |
| 12 | <h1>instance-of</h1> |
| 13 | |
| 14 | <h2>Purpose</h2> |
| 15 | |
| 16 | <p> |
| 17 | Store in the given destination register 1 if the indicated reference is an |
| 18 | instance of the given type, or 0 if not. The type must be a reference type (not |
| 19 | a primitive type). |
| 20 | </p> |
| 21 | |
| 22 | <h2>Details</h2> |
| 23 | |
| 24 | <table class="instruc"> |
| 25 | <thead> |
| 26 | <tr> |
| 27 | <th>Op & Format</th> |
| 28 | <th>Mnemonic / Syntax</th> |
| 29 | <th>Arguments</th> |
| 30 | </tr> |
| 31 | </thead> |
| 32 | <tbody> |
| 33 | <tr> |
| 34 | <td>20 22c</td> |
| 35 | <td>instance-of vA, vB, type@CCCC</td> |
| 36 | <td><code>A:</code> destination register (4 bits)<br/> |
| 37 | <code>B:</code> reference-bearing register (4 bits)<br/> |
| 38 | <code>C:</code> type index (16 bits)</td> |
| 39 | </tr> |
| 40 | </tbody> |
| 41 | </table> |
| 42 | |
| 43 | <h2>Constraints</h2> |
| 44 | |
| 45 | <ul> |
| 46 | <li> |
| 47 | Both A and B must be a valid register indices for the current stack frame. |
| 48 | </li> |
| 49 | <li> |
| 50 | Register vB must contain a reference value. |
| 51 | </li> |
| 52 | <li> |
| 53 | C must be a valid index into the type constant pool. |
| 54 | </li> |
| 55 | <li> |
| 56 | Type constant pool entry C must contain a valid type descriptor for a |
| 57 | reference type. |
| Carl Shapiro | de75089 | 2010-06-08 16:37:12 -0700 | [diff] [blame] | 58 | </li> |
| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 59 | </ul> |
| 60 | |
| 61 | <h2>Behavior</h2> |
| 62 | |
| 63 | <ul> |
| 64 | <li> |
| 65 | An attempt is made to get a reference to the class K the name of which is |
| 66 | contained in type pool entry C. |
| 67 | </li> |
| 68 | <li> |
| 69 | If K has not been loaded and resolved before, it is being loaded and |
| 70 | resolved. All exceptions that are possible during class loading can occur at |
| 71 | this point. |
| 72 | </li> |
| 73 | <li> |
| 74 | The run-time type of the object reference vB is compared against K. The |
| 75 | register vA reflects the result: |
| 76 | <ul> |
| 77 | <li> |
| 78 | vA' = 1 if (and only if) vB is not null and vB is assignment compatible |
| 79 | with K according to the usual rules of the Java programming language. |
| 80 | </li> |
| 81 | <li> |
| 82 | vA' = 0 otherwise |
| 83 | </li> |
| 84 | </ul> |
| 85 | </li> |
| 86 | <li> |
| 87 | If v(A-1) is the lower half of a register pair, v(A-1)' becomes undefined. |
| 88 | </li> |
| 89 | <li> |
| 90 | If v(A+1) is the upper half of a register pair, v(A+1)' becomes undefined. |
| Carl Shapiro | de75089 | 2010-06-08 16:37:12 -0700 | [diff] [blame] | 91 | </li> |
| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 92 | |
| 93 | <h2>Exceptions</h2> |
| 94 | |
| 95 | <p> |
| 96 | None. |
| 97 | </p> |
| 98 | |
| 99 | </body> |
| 100 | </html> |