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| <h5 class="subsubsection">9.12.2.3 Special Characters</h5> |
| |
| <p><a name="index-line-comment-character_002c-D30V-1014"></a><a name="index-D30V-line-comment-character-1015"></a>A semicolon (‘<samp><span class="samp">;</span></samp>’) can be used anywhere on a line to start a |
| comment that extends to the end of the line. |
| |
| <p>If a ‘<samp><span class="samp">#</span></samp>’ appears as the first character of a line, the whole line |
| is treated as a comment, but in this case the line could also be a |
| logical line number directive (see <a href="Comments.html#Comments">Comments</a>) or a preprocessor |
| control command (see <a href="Preprocessing.html#Preprocessing">Preprocessing</a>). |
| |
| <p><a name="index-sub_002dinstruction-ordering_002c-D30V-1016"></a><a name="index-D30V-sub_002dinstruction-ordering-1017"></a>Sub-instructions may be executed in order, in reverse-order, or in parallel. |
| Instructions listed in the standard one-per-line format will be executed |
| sequentially unless you use the ‘<samp><span class="samp">-O</span></samp>’ option. |
| |
| <p>To specify the executing order, use the following symbols: |
| <dl> |
| <dt>‘<samp><span class="samp">-></span></samp>’<dd>Sequential with instruction on the left first. |
| |
| <br><dt>‘<samp><span class="samp"><-</span></samp>’<dd>Sequential with instruction on the right first. |
| |
| <br><dt>‘<samp><span class="samp">||</span></samp>’<dd>Parallel |
| </dl> |
| |
| <p>The D30V syntax allows either one instruction per line, one instruction per line with |
| the execution symbol, or two instructions per line. For example |
| <dl> |
| <dt><code>abs r2,r3 -> abs r4,r5</code><dd>Execute these sequentially. The instruction on the right is in the right |
| container and is executed second. |
| |
| <br><dt><code>abs r2,r3 <- abs r4,r5</code><dd>Execute these reverse-sequentially. The instruction on the right is in the right |
| container, and is executed first. |
| |
| <br><dt><code>abs r2,r3 || abs r4,r5</code><dd>Execute these in parallel. |
| |
| <br><dt><code>ldw r2,@(r3,r4) ||</code><dt><code>mulx r6,r8,r9</code><dd>Two-line format. Execute these in parallel. |
| |
| <br><dt><code>mulx a0,r8,r9</code><dt><code>stw r2,@(r3,r4)</code><dd>Two-line format. Execute these sequentially unless ‘<samp><span class="samp">-O</span></samp>’ option is |
| used. If the ‘<samp><span class="samp">-O</span></samp>’ option is used, the assembler will determine if |
| the instructions could be done in parallel (the above two instructions |
| can be done in parallel), and if so, emit them as parallel instructions. |
| The assembler will put them in the proper containers. In the above |
| example, the assembler will put the ‘<samp><span class="samp">stw</span></samp>’ instruction in left |
| container and the ‘<samp><span class="samp">mulx</span></samp>’ instruction in the right container. |
| |
| <br><dt><code>stw r2,@(r3,r4) -></code><dt><code>mulx a0,r8,r9</code><dd>Two-line format. Execute the ‘<samp><span class="samp">stw</span></samp>’ instruction followed by the |
| ‘<samp><span class="samp">mulx</span></samp>’ instruction sequentially. The first instruction goes in the |
| left container and the second instruction goes into right container. |
| The assembler will give an error if the machine ordering constraints are |
| violated. |
| |
| <br><dt><code>stw r2,@(r3,r4) <-</code><dt><code>mulx a0,r8,r9</code><dd>Same as previous example, except that the ‘<samp><span class="samp">mulx</span></samp>’ instruction is |
| executed before the ‘<samp><span class="samp">stw</span></samp>’ instruction. |
| </dl> |
| |
| <p><a name="index-symbol-names_002c-_0040samp_007b_0024_007d-in-1018"></a><a name="index-g_t_0040code_007b_0024_007d-in-symbol-names-1019"></a>Since ‘<samp><span class="samp">$</span></samp>’ has no special meaning, you may use it in symbol names. |
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