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167 lines
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HTML
4 years ago
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<title>Sparc-Constants - Using as</title>
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Sparc_002dSyntax.html#Sparc_002dSyntax" title="Sparc-Syntax">
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<link rel="prev" href="Sparc_002dRegs.html#Sparc_002dRegs" title="Sparc-Regs">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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</head>
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<body>
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<div class="node">
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<a name="Sparc-Constants"></a>
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<a name="Sparc_002dConstants"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Sparc_002dRelocs.html#Sparc_002dRelocs">Sparc-Relocs</a>,
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Previous: <a rel="previous" accesskey="p" href="Sparc_002dRegs.html#Sparc_002dRegs">Sparc-Regs</a>,
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Up: <a rel="up" accesskey="u" href="Sparc_002dSyntax.html#Sparc_002dSyntax">Sparc-Syntax</a>
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<hr>
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</div>
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<h5 class="subsubsection">9.42.3.3 Constants</h5>
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<p><a name="index-Sparc-constants-2024"></a><a name="index-constants_002c-Sparc-2025"></a>
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Several Sparc instructions take an immediate operand field for
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which mnemonic names exist. Two such examples are ‘<samp><span class="samp">membar</span></samp>’
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and ‘<samp><span class="samp">prefetch</span></samp>’. Another example are the set of V9
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memory access instruction that allow specification of an
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address space identifier.
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<p>The ‘<samp><span class="samp">membar</span></samp>’ instruction specifies a memory barrier that is
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the defined by the operand which is a bitmask. The supported
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mask mnemonics are:
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<ul>
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<li>‘<samp><span class="samp">#Sync</span></samp>’ requests that all operations (including nonmemory
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reference operations) appearing prior to the <code>membar</code> must have
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been performed and the effects of any exceptions become visible before
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any instructions after the <code>membar</code> may be initiated. This
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corresponds to <code>membar</code> cmask field bit 2.
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<li>‘<samp><span class="samp">#MemIssue</span></samp>’ requests that all memory reference operations
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appearing prior to the <code>membar</code> must have been performed before
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any memory operation after the <code>membar</code> may be initiated. This
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corresponds to <code>membar</code> cmask field bit 1.
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<li>‘<samp><span class="samp">#Lookaside</span></samp>’ requests that a store appearing prior to the
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<code>membar</code> must complete before any load following the
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<code>membar</code> referencing the same address can be initiated. This
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corresponds to <code>membar</code> cmask field bit 0.
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<li>‘<samp><span class="samp">#StoreStore</span></samp>’ defines that the effects of all stores appearing
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prior to the <code>membar</code> instruction must be visible to all
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processors before the effect of any stores following the
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<code>membar</code>. Equivalent to the deprecated <code>stbar</code> instruction.
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This corresponds to <code>membar</code> mmask field bit 3.
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<li>‘<samp><span class="samp">#LoadStore</span></samp>’ defines all loads appearing prior to the
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<code>membar</code> instruction must have been performed before the effect
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of any stores following the <code>membar</code> is visible to any other
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processor. This corresponds to <code>membar</code> mmask field bit 2.
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<li>‘<samp><span class="samp">#StoreLoad</span></samp>’ defines that the effects of all stores appearing
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prior to the <code>membar</code> instruction must be visible to all
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processors before loads following the <code>membar</code> may be performed.
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This corresponds to <code>membar</code> mmask field bit 1.
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<li>‘<samp><span class="samp">#LoadLoad</span></samp>’ defines that all loads appearing prior to the
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<code>membar</code> instruction must have been performed before any loads
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following the <code>membar</code> may be performed. This corresponds to
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<code>membar</code> mmask field bit 0.
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</ul>
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<p>These values can be ored together, for example:
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<pre class="example"> membar #Sync
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membar #StoreLoad | #LoadLoad
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membar #StoreLoad | #StoreStore
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</pre>
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<p>The <code>prefetch</code> and <code>prefetcha</code> instructions take a prefetch
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function code. The following prefetch function code constant
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mnemonics are available:
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<ul>
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<li>‘<samp><span class="samp">#n_reads</span></samp>’ requests a prefetch for several reads, and corresponds
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to a prefetch function code of 0.
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<p>‘<samp><span class="samp">#one_read</span></samp>’ requests a prefetch for one read, and corresponds
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to a prefetch function code of 1.
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<p>‘<samp><span class="samp">#n_writes</span></samp>’ requests a prefetch for several writes (and possibly
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reads), and corresponds to a prefetch function code of 2.
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<p>‘<samp><span class="samp">#one_write</span></samp>’ requests a prefetch for one write, and corresponds
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to a prefetch function code of 3.
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<p>‘<samp><span class="samp">#page</span></samp>’ requests a prefetch page, and corresponds to a prefetch
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function code of 4.
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<p>‘<samp><span class="samp">#invalidate</span></samp>’ requests a prefetch invalidate, and corresponds to
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a prefetch function code of 16.
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<p>‘<samp><span class="samp">#unified</span></samp>’ requests a prefetch to the nearest unified cache, and
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corresponds to a prefetch function code of 17.
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<p>‘<samp><span class="samp">#n_reads_strong</span></samp>’ requests a strong prefetch for several reads,
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and corresponds to a prefetch function code of 20.
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<p>‘<samp><span class="samp">#one_read_strong</span></samp>’ requests a strong prefetch for one read,
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and corresponds to a prefetch function code of 21.
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<p>‘<samp><span class="samp">#n_writes_strong</span></samp>’ requests a strong prefetch for several writes,
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and corresponds to a prefetch function code of 22.
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<p>‘<samp><span class="samp">#one_write_strong</span></samp>’ requests a strong prefetch for one write,
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and corresponds to a prefetch function code of 23.
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<p>Onle one prefetch code may be specified. Here are some examples:
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<pre class="example"> prefetch [%l0 + %l2], #one_read
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prefetch [%g2 + 8], #n_writes
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prefetcha [%g1] 0x8, #unified
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prefetcha [%o0 + 0x10] %asi, #n_reads
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</pre>
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<p>The actual behavior of a given prefetch function code is processor
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specific. If a processor does not implement a given prefetch
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function code, it will treat the prefetch instruction as a nop.
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<p>For instructions that accept an immediate address space identifier,
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<code>as</code> provides many mnemonics corresponding to
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V9 defined as well as UltraSPARC and Niagara extended values.
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For example, ‘<samp><span class="samp">#ASI_P</span></samp>’ and ‘<samp><span class="samp">#ASI_BLK_INIT_QUAD_LDD_AIUS</span></samp>’.
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See the V9 and processor specific manuals for details.
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</ul>
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</body></html>
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