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<a name="s390-Formats"></a>
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<hr>
<a name="Instruction-Formats-1"></a>
<h4 class="subsubsection">9.40.3.4 Instruction Formats</h4>
<a name="index-instruction-formats_002c-s390"></a>
<a name="index-s390-instruction-formats"></a>
<p>The Principles of Operation manuals lists 26 instruction formats where
some of the formats have multiple variants. For the ‘<samp>.insn</samp>’
pseudo directive the assembler recognizes some of the formats.
Typically, the most general variant of the instruction format is used
by the ‘<samp>.insn</samp>’ directive.
</p>
<p>The following table lists the abbreviations used in the table of
instruction formats:
</p>
<div class="display">
<table>
<tr><td><pre class="display">OpCode / OpCd</pre></td><td><pre class="display">Part of the op code.</pre></td></tr>
<tr><td><pre class="display">Bx</pre></td><td><pre class="display">Base register number for operand x.</pre></td></tr>
<tr><td><pre class="display">Dx</pre></td><td><pre class="display">Displacement for operand x.</pre></td></tr>
<tr><td><pre class="display">DLx</pre></td><td><pre class="display">Displacement lower 12 bits for operand x.</pre></td></tr>
<tr><td><pre class="display">DHx</pre></td><td><pre class="display">Displacement higher 8-bits for operand x.</pre></td></tr>
<tr><td><pre class="display">Rx</pre></td><td><pre class="display">Register number for operand x.</pre></td></tr>
<tr><td><pre class="display">Xx</pre></td><td><pre class="display">Index register number for operand x.</pre></td></tr>
<tr><td><pre class="display">Ix</pre></td><td><pre class="display">Signed immediate for operand x.</pre></td></tr>
<tr><td><pre class="display">Ux</pre></td><td><pre class="display">Unsigned immediate for operand x.</pre></td></tr>
</table>
</div>
<p>An instruction is two, four, or six bytes in length and must be aligned
on a 2 byte boundary. The first two bits of the instruction specify the
length of the instruction, 00 indicates a two byte instruction, 01 and 10
indicates a four byte instruction, and 11 indicates a six byte instruction.
</p>
<p>The following table lists the s390 instruction formats that are available
with the ‘<samp>.insn</samp>’ pseudo directive:
</p>
<dl compact="compact">
<dt><code>E format</code></dt>
<dd><pre class="verbatim">+-------------+
| OpCode |
+-------------+
0 15
</pre>
</dd>
<dt><code>RI format: <insn> R1,I2</code></dt>
<dd><pre class="verbatim">+--------+----+----+------------------+
| OpCode | R1 |OpCd| I2 |
+--------+----+----+------------------+
0 8 12 16 31
</pre>
</dd>
<dt><code>RIE format: <insn> R1,R3,I2</code></dt>
<dd><pre class="verbatim">+--------+----+----+------------------+--------+--------+
| OpCode | R1 | R3 | I2 |////////| OpCode |
+--------+----+----+------------------+--------+--------+
0 8 12 16 32 40 47
</pre>
</dd>
<dt><code>RIL format: <insn> R1,I2</code></dt>
<dd><pre class="verbatim">+--------+----+----+------------------------------------+
| OpCode | R1 |OpCd| I2 |
+--------+----+----+------------------------------------+
0 8 12 16 47
</pre>
</dd>
<dt><code>RILU format: <insn> R1,U2</code></dt>
<dd><pre class="verbatim">+--------+----+----+------------------------------------+
| OpCode | R1 |OpCd| U2 |
+--------+----+----+------------------------------------+
0 8 12 16 47
</pre>
</dd>
<dt><code>RIS format: <insn> R1,I2,M3,D4(B4)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+--------+--------+
| OpCode | R1 | M3 | B4 | D4 | I2 | Opcode |
+--------+----+----+----+-------------+--------+--------+
0 8 12 16 20 32 36 47
</pre>
</dd>
<dt><code>RR format: <insn> R1,R2</code></dt>
<dd><pre class="verbatim">+--------+----+----+
| OpCode | R1 | R2 |
+--------+----+----+
0 8 12 15
</pre>
</dd>
<dt><code>RRE format: <insn> R1,R2</code></dt>
<dd><pre class="verbatim">+------------------+--------+----+----+
| OpCode |////////| R1 | R2 |
+------------------+--------+----+----+
0 16 24 28 31
</pre>
</dd>
<dt><code>RRF format: <insn> R1,R2,R3,M4</code></dt>
<dd><pre class="verbatim">+------------------+----+----+----+----+
| OpCode | R3 | M4 | R1 | R2 |
+------------------+----+----+----+----+
0 16 20 24 28 31
</pre>
</dd>
<dt><code>RRS format: <insn> R1,R2,M3,D4(B4)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+----+----+--------+
| OpCode | R1 | R3 | B4 | D4 | M3 |////| OpCode |
+--------+----+----+----+-------------+----+----+--------+
0 8 12 16 20 32 36 40 47
</pre>
</dd>
<dt><code>RS format: <insn> R1,R3,D2(B2)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+
| OpCode | R1 | R3 | B2 | D2 |
+--------+----+----+----+-------------+
0 8 12 16 20 31
</pre>
</dd>
<dt><code>RSE format: <insn> R1,R3,D2(B2)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+--------+--------+
| OpCode | R1 | R3 | B2 | D2 |////////| OpCode |
+--------+----+----+----+-------------+--------+--------+
0 8 12 16 20 32 40 47
</pre>
</dd>
<dt><code>RSI format: <insn> R1,R3,I2</code></dt>
<dd><pre class="verbatim">+--------+----+----+------------------------------------+
| OpCode | R1 | R3 | I2 |
+--------+----+----+------------------------------------+
0 8 12 16 47
</pre>
</dd>
<dt><code>RSY format: <insn> R1,R3,D2(B2)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+--------+--------+
| OpCode | R1 | R3 | B2 | DL2 | DH2 | OpCode |
+--------+----+----+----+-------------+--------+--------+
0 8 12 16 20 32 40 47
</pre>
</dd>
<dt><code>RX format: <insn> R1,D2(X2,B2)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+
| OpCode | R1 | X2 | B2 | D2 |
+--------+----+----+----+-------------+
0 8 12 16 20 31
</pre>
</dd>
<dt><code>RXE format: <insn> R1,D2(X2,B2)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+--------+--------+
| OpCode | R1 | X2 | B2 | D2 |////////| OpCode |
+--------+----+----+----+-------------+--------+--------+
0 8 12 16 20 32 40 47
</pre>
</dd>
<dt><code>RXF format: <insn> R1,R3,D2(X2,B2)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+----+---+--------+
| OpCode | R3 | X2 | B2 | D2 | R1 |///| OpCode |
+--------+----+----+----+-------------+----+---+--------+
0 8 12 16 20 32 36 40 47
</pre>
</dd>
<dt><code>RXY format: <insn> R1,D2(X2,B2)</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+--------+--------+
| OpCode | R1 | X2 | B2 | DL2 | DH2 | OpCode |
+--------+----+----+----+-------------+--------+--------+
0 8 12 16 20 32 36 40 47
</pre>
</dd>
<dt><code>S format: <insn> D2(B2)</code></dt>
<dd><pre class="verbatim">+------------------+----+-------------+
| OpCode | B2 | D2 |
+------------------+----+-------------+
0 16 20 31
</pre>
</dd>
<dt><code>SI format: <insn> D1(B1),I2</code></dt>
<dd><pre class="verbatim">+--------+---------+----+-------------+
| OpCode | I2 | B1 | D1 |
+--------+---------+----+-------------+
0 8 16 20 31
</pre>
</dd>
<dt><code>SIY format: <insn> D1(B1),U2</code></dt>
<dd><pre class="verbatim">+--------+---------+----+-------------+--------+--------+
| OpCode | I2 | B1 | DL1 | DH1 | OpCode |
+--------+---------+----+-------------+--------+--------+
0 8 16 20 32 36 40 47
</pre>
</dd>
<dt><code>SIL format: <insn> D1(B1),I2</code></dt>
<dd><pre class="verbatim">+------------------+----+-------------+-----------------+
| OpCode | B1 | D1 | I2 |
+------------------+----+-------------+-----------------+
0 16 20 32 47
</pre>
</dd>
<dt><code>SS format: <insn> D1(R1,B1),D2(B3),R3</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+----+------------+
| OpCode | R1 | R3 | B1 | D1 | B2 | D2 |
+--------+----+----+----+-------------+----+------------+
0 8 12 16 20 32 36 47
</pre>
</dd>
<dt><code>SSE format: <insn> D1(B1),D2(B2)</code></dt>
<dd><pre class="verbatim">+------------------+----+-------------+----+------------+
| OpCode | B1 | D1 | B2 | D2 |
+------------------+----+-------------+----+------------+
0 8 12 16 20 32 36 47
</pre>
</dd>
<dt><code>SSF format: <insn> D1(B1),D2(B2),R3</code></dt>
<dd><pre class="verbatim">+--------+----+----+----+-------------+----+------------+
| OpCode | R3 |OpCd| B1 | D1 | B2 | D2 |
+--------+----+----+----+-------------+----+------------+
0 8 12 16 20 32 36 47
</pre>
</dd>
</dl>
<p>For the complete list of all instruction format variants see the
Principles of Operation manuals.
</p>
<hr>
<div class="header">
<p>
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