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| <h5 class="subsubsection">9.20.2.1 Symbolic Operand Modifiers</h5> |
| |
| <p><a name="index-M32C-modifiers-1343"></a><a name="index-modifiers_002c-M32C-1344"></a> |
| The assembler supports several modifiers when using symbol addresses |
| in M32C instruction operands. The general syntax is the following: |
| |
| <pre class="smallexample"> %modifier(symbol) |
| </pre> |
| |
| <a name="index-symbol-modifiers-1345"></a> |
| <dl> |
| <dt><code>%dsp8</code><dt><code>%dsp16</code><dd> |
| These modifiers override the assembler's assumptions about how big a |
| symbol's address is. Normally, when it sees an operand like |
| ‘<samp><span class="samp">sym[a0]</span></samp>’ it assumes ‘<samp><span class="samp">sym</span></samp>’ may require the widest |
| displacement field (16 bits for ‘<samp><span class="samp">-m16c</span></samp>’, 24 bits for |
| ‘<samp><span class="samp">-m32c</span></samp>’). These modifiers tell it to assume the address will fit |
| in an 8 or 16 bit (respectively) unsigned displacement. Note that, of |
| course, if it doesn't actually fit you will get linker errors. Example: |
| |
| <pre class="smallexample"> mov.w %dsp8(sym)[a0],r1 |
| mov.b #0,%dsp8(sym)[a0] |
| </pre> |
| <br><dt><code>%hi8</code><dd> |
| This modifier allows you to load bits 16 through 23 of a 24 bit |
| address into an 8 bit register. This is useful with, for example, the |
| M16C ‘<samp><span class="samp">smovf</span></samp>’ instruction, which expects a 20 bit address in |
| ‘<samp><span class="samp">r1h</span></samp>’ and ‘<samp><span class="samp">a0</span></samp>’. Example: |
| |
| <pre class="smallexample"> mov.b #%hi8(sym),r1h |
| mov.w #%lo16(sym),a0 |
| smovf.b |
| </pre> |
| <br><dt><code>%lo16</code><dd> |
| Likewise, this modifier allows you to load bits 0 through 15 of a 24 |
| bit address into a 16 bit register. |
| |
| <br><dt><code>%hi16</code><dd> |
| This modifier allows you to load bits 16 through 31 of a 32 bit |
| address into a 16 bit register. While the M32C family only has 24 |
| bits of address space, it does support addresses in pairs of 16 bit |
| registers (like ‘<samp><span class="samp">a1a0</span></samp>’ for the ‘<samp><span class="samp">lde</span></samp>’ instruction). This |
| modifier is for loading the upper half in such cases. Example: |
| |
| <pre class="smallexample"> mov.w #%hi16(sym),a1 |
| mov.w #%lo16(sym),a0 |
| ... |
| lde.w [a1a0],r1 |
| </pre> |
| </dl> |
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