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| <a name="Constants-2"></a> |
| <h4 class="subsubsection">9.41.3.3 Constants</h4> |
| <a name="index-Sparc-constants"></a> |
| <a name="index-constants_002c-Sparc"></a> |
| |
| <p>Several Sparc instructions take an immediate operand field for |
| which mnemonic names exist. Two such examples are ‘<samp>membar</samp>’ |
| and ‘<samp>prefetch</samp>’. Another example are the set of V9 |
| memory access instruction that allow specification of an |
| address space identifier. |
| </p> |
| <p>The ‘<samp>membar</samp>’ instruction specifies a memory barrier that is |
| the defined by the operand which is a bitmask. The supported |
| mask mnemonics are: |
| </p> |
| <ul> |
| <li> ‘<samp>#Sync</samp>’ requests that all operations (including nonmemory |
| reference operations) appearing prior to the <code>membar</code> must have |
| been performed and the effects of any exceptions become visible before |
| any instructions after the <code>membar</code> may be initiated. This |
| corresponds to <code>membar</code> cmask field bit 2. |
| |
| </li><li> ‘<samp>#MemIssue</samp>’ requests that all memory reference operations |
| appearing prior to the <code>membar</code> must have been performed before |
| any memory operation after the <code>membar</code> may be initiated. This |
| corresponds to <code>membar</code> cmask field bit 1. |
| |
| </li><li> ‘<samp>#Lookaside</samp>’ requests that a store appearing prior to the |
| <code>membar</code> must complete before any load following the |
| <code>membar</code> referencing the same address can be initiated. This |
| corresponds to <code>membar</code> cmask field bit 0. |
| |
| </li><li> ‘<samp>#StoreStore</samp>’ defines that the effects of all stores appearing |
| prior to the <code>membar</code> instruction must be visible to all |
| processors before the effect of any stores following the |
| <code>membar</code>. Equivalent to the deprecated <code>stbar</code> instruction. |
| This corresponds to <code>membar</code> mmask field bit 3. |
| |
| </li><li> ‘<samp>#LoadStore</samp>’ defines all loads appearing prior to the |
| <code>membar</code> instruction must have been performed before the effect |
| of any stores following the <code>membar</code> is visible to any other |
| processor. This corresponds to <code>membar</code> mmask field bit 2. |
| |
| </li><li> ‘<samp>#StoreLoad</samp>’ defines that the effects of all stores appearing |
| prior to the <code>membar</code> instruction must be visible to all |
| processors before loads following the <code>membar</code> may be performed. |
| This corresponds to <code>membar</code> mmask field bit 1. |
| |
| </li><li> ‘<samp>#LoadLoad</samp>’ defines that all loads appearing prior to the |
| <code>membar</code> instruction must have been performed before any loads |
| following the <code>membar</code> may be performed. This corresponds to |
| <code>membar</code> mmask field bit 0. |
| |
| </li></ul> |
| |
| <p>These values can be ored together, for example: |
| </p> |
| <div class="example"> |
| <pre class="example">membar #Sync |
| membar #StoreLoad | #LoadLoad |
| membar #StoreLoad | #StoreStore |
| </pre></div> |
| |
| <p>The <code>prefetch</code> and <code>prefetcha</code> instructions take a prefetch |
| function code. The following prefetch function code constant |
| mnemonics are available: |
| </p> |
| <ul> |
| <li> ‘<samp>#n_reads</samp>’ requests a prefetch for several reads, and corresponds |
| to a prefetch function code of 0. |
| |
| <p>‘<samp>#one_read</samp>’ requests a prefetch for one read, and corresponds |
| to a prefetch function code of 1. |
| </p> |
| <p>‘<samp>#n_writes</samp>’ requests a prefetch for several writes (and possibly |
| reads), and corresponds to a prefetch function code of 2. |
| </p> |
| <p>‘<samp>#one_write</samp>’ requests a prefetch for one write, and corresponds |
| to a prefetch function code of 3. |
| </p> |
| <p>‘<samp>#page</samp>’ requests a prefetch page, and corresponds to a prefetch |
| function code of 4. |
| </p> |
| <p>‘<samp>#invalidate</samp>’ requests a prefetch invalidate, and corresponds to |
| a prefetch function code of 16. |
| </p> |
| <p>‘<samp>#unified</samp>’ requests a prefetch to the nearest unified cache, and |
| corresponds to a prefetch function code of 17. |
| </p> |
| <p>‘<samp>#n_reads_strong</samp>’ requests a strong prefetch for several reads, |
| and corresponds to a prefetch function code of 20. |
| </p> |
| <p>‘<samp>#one_read_strong</samp>’ requests a strong prefetch for one read, |
| and corresponds to a prefetch function code of 21. |
| </p> |
| <p>‘<samp>#n_writes_strong</samp>’ requests a strong prefetch for several writes, |
| and corresponds to a prefetch function code of 22. |
| </p> |
| <p>‘<samp>#one_write_strong</samp>’ requests a strong prefetch for one write, |
| and corresponds to a prefetch function code of 23. |
| </p> |
| <p>Onle one prefetch code may be specified. Here are some examples: |
| </p> |
| <div class="example"> |
| <pre class="example">prefetch [%l0 + %l2], #one_read |
| prefetch [%g2 + 8], #n_writes |
| prefetcha [%g1] 0x8, #unified |
| prefetcha [%o0 + 0x10] %asi, #n_reads |
| </pre></div> |
| |
| <p>The actual behavior of a given prefetch function code is processor |
| specific. If a processor does not implement a given prefetch |
| function code, it will treat the prefetch instruction as a nop. |
| </p> |
| <p>For instructions that accept an immediate address space identifier, |
| <code>as</code> provides many mnemonics corresponding to |
| V9 defined as well as UltraSPARC and Niagara extended values. |
| For example, ‘<samp>#ASI_P</samp>’ and ‘<samp>#ASI_BLK_INIT_QUAD_LDD_AIUS</samp>’. |
| See the V9 and processor specific manuals for details. |
| </p> |
| </li></ul> |
| |
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