| <html lang="en"> |
| <head> |
| <title>s390 Operands - Using as</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Using as"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="s390-Syntax.html#s390-Syntax" title="s390 Syntax"> |
| <link rel="prev" href="s390-Mnemonics.html#s390-Mnemonics" title="s390 Mnemonics"> |
| <link rel="next" href="s390-Formats.html#s390-Formats" title="s390 Formats"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU Assembler "as". |
| |
| Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, |
| 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 |
| or any later version published by the Free Software Foundation; |
| with no Invariant Sections, with no Front-Cover Texts, and with no |
| Back-Cover Texts. A copy of the license is included in the |
| section entitled ``GNU Free Documentation License''. |
| |
| --> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="s390-Operands"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="s390-Formats.html#s390-Formats">s390 Formats</a>, |
| Previous: <a rel="previous" accesskey="p" href="s390-Mnemonics.html#s390-Mnemonics">s390 Mnemonics</a>, |
| Up: <a rel="up" accesskey="u" href="s390-Syntax.html#s390-Syntax">s390 Syntax</a> |
| <hr> |
| </div> |
| |
| <h5 class="subsubsection">9.31.3.3 Instruction Operands</h5> |
| |
| <p><a name="index-instruction-operands_002c-s390-1538"></a><a name="index-s390-instruction-operands-1539"></a> |
| Instruction operands can be grouped into three classes, operands located |
| in registers, immediate operands, and operands in storage. |
| |
| <p>A register operand can be located in general, floating-point, access, |
| or control register. The register is identified by a four-bit field. |
| The field containing the register operand is called the R field. |
| |
| <p>Immediate operands are contained within the instruction and can have |
| 8, 16 or 32 bits. The field containing the immediate operand is called |
| the I field. Dependent on the instruction the I field is either signed |
| or unsigned. |
| |
| <p>A storage operand consists of an address and a length. The address of a |
| storage operands can be specified in any of these ways: |
| |
| <ul> |
| <li>The content of a single general R |
| <li>The sum of the content of a general register called the base |
| register B plus the content of a displacement field D |
| <li>The sum of the contents of two general registers called the |
| index register X and the base register B plus the content of a |
| displacement field |
| <li>The sum of the current instruction address and a 32-bit signed |
| immediate field multiplied by two. |
| </ul> |
| |
| <p>The length of a storage operand can be: |
| |
| <ul> |
| <li>Implied by the instruction |
| <li>Specified by a bitmask |
| <li>Specified by a four-bit or eight-bit length field L |
| <li>Specified by the content of a general register |
| </ul> |
| |
| <p>The notation for storage operand addresses formed from multiple fields is |
| as follows: |
| |
| <dl> |
| <dt><code>Dn(Bn)</code><dd>the address for operand number n is formed from the content of general |
| register Bn called the base register and the displacement field Dn. |
| <br><dt><code>Dn(Xn,Bn)</code><dd>the address for operand number n is formed from the content of general |
| register Xn called the index register, general register Bn called the |
| base register and the displacement field Dn. |
| <br><dt><code>Dn(Ln,Bn)</code><dd>the address for operand number n is formed from the content of general |
| regiser Bn called the base register and the displacement field Dn. |
| The length of the operand n is specified by the field Ln. |
| </dl> |
| |
| <p>The base registers Bn and the index registers Xn of a storage operand can |
| be skipped. If Bn and Xn are skipped, a zero will be stored to the operand |
| field. The notation changes as follows: |
| |
| <pre class="display"> |
| <p><table summary=""><tr align="left"><th valign="top" width="30%">full notation </th><th valign="top" width="30%">short notation |
| <br></th></tr><tr align="left"><td valign="top" width="30%">Dn(0,Bn) </td><td valign="top" width="30%">Dn(Bn) |
| <br></td></tr><tr align="left"><td valign="top" width="30%">Dn(0,0) </td><td valign="top" width="30%">Dn |
| <br></td></tr><tr align="left"><td valign="top" width="30%">Dn(0) </td><td valign="top" width="30%">Dn |
| <br></td></tr><tr align="left"><td valign="top" width="30%">Dn(Ln,0) </td><td valign="top" width="30%">Dn(Ln) |
| <br></td></tr></table> |
| </pre> |
| </body></html> |
| |
