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| <title>const</title> |
| <link rel=stylesheet href="opcode.css"> |
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| <body> |
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| <h1>const</h1> |
| |
| <h2>Purpose</h2> |
| |
| <p> |
| Move the given literal value (sign-extended to 32 bits, if necessary) into the |
| specified register. |
| </p> |
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| <h2>Details</h2> |
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| <table class="instruc"> |
| <thead> |
| <tr> |
| <th>Op & Format</th> |
| <th>Mnemonic / Syntax</th> |
| <th>Arguments</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td>12 11n</td> |
| <td>const/4 vA, #+B</td> |
| <td><code>A:</code> destination register (4 bits)<br/> |
| <code>B:</code> signed int (4 bits)</td> |
| </tr> |
| <tr> |
| <td>13 21s</td> |
| <td>const/16 vAA, #+BBBB</td> |
| <td><code>A:</code> destination register (8 bits)<br/> |
| <code>B:</code> signed int (16 bits)</td> |
| </tr> |
| <tr> |
| <td>14 31i</td> |
| <td>const vAA, #+BBBBBBBB</td> |
| <td><code>A:</code> destination register (8 bits)<br/> |
| <code>B:</code> arbitrary 32-bit constant</td> |
| </tr> |
| <tr> |
| <td>15 21h</td> |
| <td>const/high16 vAA, #+BBBB0000</td> |
| <td><code>A:</code> destination register (8 bits)<br/> |
| <code>B:</code> signed int (16 bits)</td> |
| </tr> |
| </tbody> |
| </table> |
| |
| <h2>Constraints</h2> |
| |
| <ul> |
| <li> |
| A must be a valid register index in the current stackframe. |
| </li> |
| </ul> |
| |
| <h2>Behavior</h2> |
| |
| <ul> |
| <li> |
| First, an adjusted value B' is determined as follows: |
| <ul> |
| <li> |
| If we are executing the /high16 variant, then B is left-shifted by 16 |
| bits, that is, B'=B << 0x10 |
| <li> |
| Otherwise, if B is a 4 bit or 16 bit constant, it is sign-extended to 32 |
| bits, that is, B'=sign-extended(B). |
| </li> |
| <li> |
| Otherwise, B'=B. |
| </li> |
| </ul> |
| <li> |
| Then, the adjusted value B' is moved into the register A, that is, vA'=B' |
| </li> |
| <li> |
| If v(A-1) is the lower half of a register pair, v(A-1)' becomes undefined. |
| </li> |
| <li> |
| If v(A+1) is the upper half of a register pair, v(A+1)' becomes undefined. |
| </li> |
| </ul> |
| |
| <h2>Exceptions</h2> |
| |
| <p> |
| None. |
| </p> |
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