96 lines
3.9 KiB
HTML
96 lines
3.9 KiB
HTML
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<!DOCTYPE html>
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<html>
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<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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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 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
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copy of the license is included in the section entitled "GNU Free
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Documentation License." -->
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<title>VM Concepts (Guile Reference Manual)</title>
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<meta name="description" content="VM Concepts (Guile Reference Manual)">
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<meta name="keywords" content="VM Concepts (Guile Reference Manual)">
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<meta name="viewport" content="width=device-width,initial-scale=1">
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="A-Virtual-Machine-for-Guile.html" rel="up" title="A Virtual Machine for Guile">
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<link href="Stack-Layout.html" rel="next" title="Stack Layout">
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<link href="Why-a-VM_003f.html" rel="prev" title="Why a VM?">
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</style>
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<link rel="stylesheet" type="text/css" href="https://www.gnu.org/software/gnulib/manual.css">
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</head>
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<body lang="en">
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<div class="subsection-level-extent" id="VM-Concepts">
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<div class="nav-panel">
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<p>
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Next: <a href="Stack-Layout.html" accesskey="n" rel="next">Stack Layout</a>, Previous: <a href="Why-a-VM_003f.html" accesskey="p" rel="prev">Why a VM?</a>, Up: <a href="A-Virtual-Machine-for-Guile.html" accesskey="u" rel="up">A Virtual Machine for Guile</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<h4 class="subsection" id="VM-Concepts-1"><span>9.3.2 VM Concepts<a class="copiable-link" href="#VM-Concepts-1"> ¶</a></span></h4>
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<p>The bytecode in a Scheme procedure is interpreted by a virtual machine
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(VM). Each thread has its own instantiation of the VM. The virtual
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machine executes the sequence of instructions in a procedure.
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</p>
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<p>Each VM instruction starts by indicating which operation it is, and then
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follows by encoding its source and destination operands. Each procedure
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declares that it has some number of local variables, including the
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function arguments. These local variables form the available operands
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of the procedure, and are accessed by index.
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</p>
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<p>The local variables for a procedure are stored on a stack. Calling a
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procedure typically enlarges the stack, and returning from a procedure
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shrinks it. Stack memory is exclusive to the virtual machine that owns
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it.
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</p>
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<p>In addition to their stacks, virtual machines also have access to the
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global memory (modules, global bindings, etc) that is shared among other
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parts of Guile, including other VMs.
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</p>
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<p>The registers that a VM has are as follows:
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</p>
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<ul class="itemize mark-bullet">
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<li>ip - Instruction pointer
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</li><li>sp - Stack pointer
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</li><li>fp - Frame pointer
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</li></ul>
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<p>In other architectures, the instruction pointer is sometimes called the
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“program counter” (pc). This set of registers is pretty typical for
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virtual machines; their exact meanings in the context of Guile’s VM are
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described in the next section.
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</p>
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</div>
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</body>
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</html>
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