| The Android Open Source Project | 89c1feb | 2008-12-17 18:03:55 -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>const</title> |
| 7 | <link rel=stylesheet href="opcode.css"> |
| 8 | </head> |
| 9 | |
| 10 | <body> |
| 11 | |
| 12 | <h1>const</h1> |
| 13 | |
| 14 | <h2>Purpose</h2> |
| 15 | |
| 16 | <p> |
| 17 | Move the given literal value (sign-extended to 32 bits, if necessary) into the |
| 18 | specified register. |
| 19 | </p> |
| 20 | |
| 21 | <h2>Details</h2> |
| 22 | |
| 23 | <table class="instruc"> |
| 24 | <thead> |
| 25 | <tr> |
| 26 | <th>Op & Format</th> |
| 27 | <th>Mnemonic / Syntax</th> |
| 28 | <th>Arguments</th> |
| 29 | </tr> |
| 30 | </thead> |
| 31 | <tbody> |
| 32 | <tr> |
| 33 | <td>12 11n</td> |
| 34 | <td>const/4 vA, #+B</td> |
| 35 | <td><code>A:</code> destination register (4 bits)<br/> |
| 36 | <code>B:</code> signed int (4 bits)</td> |
| 37 | </tr> |
| 38 | <tr> |
| 39 | <td>13 21s</td> |
| 40 | <td>const/16 vAA, #+BBBB</td> |
| 41 | <td><code>A:</code> destination register (8 bits)<br/> |
| 42 | <code>B:</code> signed int (16 bits)</td> |
| 43 | </tr> |
| 44 | <tr> |
| 45 | <td>14 31i</td> |
| 46 | <td>const vAA, #+BBBBBBBB</td> |
| 47 | <td><code>A:</code> destination register (8 bits)<br/> |
| 48 | <code>B:</code> arbitrary 32-bit constant</td> |
| 49 | </tr> |
| 50 | <tr> |
| 51 | <td>15 21h</td> |
| 52 | <td>const/high16 vAA, #+BBBB0000</td> |
| 53 | <td><code>A:</code> destination register (8 bits)<br/> |
| 54 | <code>B:</code> signed int (16 bits)</td> |
| 55 | </tr> |
| 56 | </tbody> |
| 57 | </table> |
| 58 | |
| 59 | <h2>Constraints</h2> |
| 60 | |
| 61 | <ul> |
| 62 | <li> |
| 63 | A must be a valid register index in the current stackframe. |
| 64 | </li> |
| 65 | </ul> |
| 66 | |
| 67 | <h2>Behavior</h2> |
| 68 | |
| 69 | <ul> |
| 70 | <li> |
| 71 | First, an adjusted value B' is determined as follows: |
| 72 | <ul> |
| 73 | <li> |
| 74 | If we are executing the /high16 variant, then B is left-shifted by 16 |
| 75 | bits, that is, B'=B << 0x10 |
| 76 | <li> |
| 77 | Otherwise, if B is a 4 bit or 16 bit constant, it is sign-extended to 32 |
| 78 | bits, that is, B'=sign-extended(B). |
| 79 | </li> |
| 80 | <li> |
| 81 | Otherwise, B'=B. |
| 82 | </li> |
| 83 | </ul> |
| 84 | <li> |
| 85 | Then, the adjusted value B' is moved into the register A, that is, vA'=B' |
| 86 | </li> |
| 87 | <li> |
| 88 | If v(A-1) is the lower half of a register pair, v(A-1)' becomes undefined. |
| 89 | </li> |
| 90 | <li> |
| 91 | If v(A+1) is the upper half of a register pair, v(A+1)' becomes undefined. |
| 92 | </li> |
| 93 | </ul> |
| 94 | |
| 95 | <h2>Exceptions</h2> |
| 96 | |
| 97 | <p> |
| 98 | None. |
| 99 | </p> |
| 100 | |
| 101 | </body> |
| 102 | </html> |