| 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>if-<test>z</title> |
| 7 | <link rel=stylesheet href="opcode.css"> |
| 8 | </head> |
| 9 | |
| 10 | <body> |
| 11 | |
| 12 | <h1>if-<test>z</h1> |
| 13 | |
| 14 | <h2>Purpose</h2> |
| 15 | |
| 16 | <p> |
| 17 | Branch to the given destination if the given register's value compares with 0 |
| 18 | as specified. |
| 19 | </p> |
| 20 | <p> |
| 21 | Note: The branch offset may not be 0. (A spin loop may be legally constructed |
| 22 | either by branching around a backward goto or by including a nop as a target |
| Carl Shapiro | de75089 | 2010-06-08 16:37:12 -0700 | [diff] [blame] | 23 | before the branch.) |
| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 24 | </p> |
| 25 | |
| 26 | <h2>Details</h2> |
| 27 | |
| 28 | <table class="instruc"> |
| 29 | <thead> |
| 30 | <tr> |
| 31 | <th>Op & Format</th> |
| 32 | <th>Mnemonic / Syntax</th> |
| 33 | <th>Arguments</th> |
| 34 | </tr> |
| 35 | </thead> |
| 36 | <tbody> |
| 37 | <tr> |
| 38 | <td>38..3d 21t</td> |
| 39 | <td>if-<i>test</i>z vAA, +BBBB<br/> |
| 40 | 38: if-eqz<br/> |
| 41 | 39: if-nez<br/> |
| 42 | 3a: if-ltz<br/> |
| 43 | 3b: if-gez<br/> |
| 44 | 3c: if-gtz<br/> |
| 45 | 3d: if-lez<br/> |
| 46 | </td> |
| 47 | <td><code>A:</code> register to test (8 bits)<br/> |
| 48 | <code>B:</code> signed branch offset (16 bits)</td> |
| 49 | </tr> |
| 50 | </tbody> |
| 51 | </table> |
| 52 | |
| 53 | <h2>Constraints</h2> |
| 54 | |
| 55 | <ul> |
| 56 | <li> |
| 57 | A must be a valid register index for the current stackframe. |
| 58 | </li> |
| 59 | <li> |
| 60 | Register vA must not contain a reference value. |
| 61 | </li> |
| 62 | <li> |
| 63 | Register vA must not be part of a register pair. |
| 64 | </li> |
| 65 | <li> |
| 66 | Register vA must not contain a floating point value (???). |
| 67 | </li> |
| 68 | <li> |
| 69 | B must not be 0. |
| Carl Shapiro | de75089 | 2010-06-08 16:37:12 -0700 | [diff] [blame] | 70 | </li> |
| The Android Open Source Project | f6c3871 | 2009-03-03 19:28:47 -0800 | [diff] [blame] | 71 | </ul> |
| 72 | |
| 73 | <h2>Behavior</h2> |
| 74 | |
| 75 | <ul> |
| 76 | <li> |
| 77 | The value of register vA is compared to zero according to the <test> |
| 78 | condition. Two results are possible: |
| 79 | <ul> |
| 80 | <li> |
| 81 | The condition holds. The value of B is used as a signed offset to the |
| 82 | address of the if-<test>z instruction. Execution continues at the |
| 83 | resulting address. |
| 84 | </li> |
| 85 | <li> |
| 86 | The condition does not hold. Execution continues at the instruction |
| 87 | following the if-<test>z instruction. |
| 88 | </li> |
| 89 | </ul> |
| 90 | </li> |
| 91 | </ul> |
| 92 | |
| 93 | <h2>Exceptions</h2> |
| 94 | |
| 95 | <p> |
| 96 | None. |
| 97 | </p> |
| 98 | |
| 99 | </body> |
| 100 | </html> |