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      6 <title>const</title>
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     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 &amp; 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 
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