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diff --git a/share/doc/gccint/Patterns.html b/share/doc/gccint/Patterns.html new file mode 100644 index 0000000..d387fad --- /dev/null +++ b/share/doc/gccint/Patterns.html @@ -0,0 +1,187 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 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 the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>GNU Compiler Collection (GCC) Internals: Patterns</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Patterns"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Patterns"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Machine-Desc.html#Machine-Desc" rel="up" title="Machine Desc"> +<link href="Example.html#Example" rel="next" title="Example"> +<link href="Overview.html#Overview" rel="previous" title="Overview"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Patterns"></a> +<div class="header"> +<p> +Next: <a href="Example.html#Example" accesskey="n" rel="next">Example</a>, Previous: <a href="Overview.html#Overview" accesskey="p" rel="previous">Overview</a>, Up: <a href="Machine-Desc.html#Machine-Desc" accesskey="u" rel="up">Machine Desc</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Everything-about-Instruction-Patterns"></a> +<h3 class="section">17.2 Everything about Instruction Patterns</h3> +<a name="index-patterns"></a> +<a name="index-instruction-patterns"></a> + +<a name="index-define_005finsn"></a> +<p>A <code>define_insn</code> expression is used to define instruction patterns +to which insns may be matched. A <code>define_insn</code> expression contains +an incomplete RTL expression, with pieces to be filled in later, operand +constraints that restrict how the pieces can be filled in, and an output +template or C code to generate the assembler output. +</p> +<p>A <code>define_insn</code> is an RTL expression containing four or five operands: +</p> +<ol> +<li> An optional name <var>n</var>. When a name is present, the compiler +automically generates a C++ function ‘<samp>gen_<var>n</var></samp>’ that takes +the operands of the instruction as arguments and returns the instruction’s +rtx pattern. The compiler also assigns the instruction a unique code +‘<samp>CODE_FOR_<var>n</var></samp>’, with all such codes belonging to an enum +called <code>insn_code</code>. + +<p>These names serve one of two purposes. The first is to indicate that the +instruction performs a certain standard job for the RTL-generation +pass of the compiler, such as a move, an addition, or a conditional +jump. The second is to help the target generate certain target-specific +operations, such as when implementing target-specific intrinsic functions. +</p> +<p>It is better to prefix target-specific names with the name of the +target, to avoid any clash with current or future standard names. +</p> +<p>The absence of a name is indicated by writing an empty string +where the name should go. Nameless instruction patterns are never +used for generating RTL code, but they may permit several simpler insns +to be combined later on. +</p> +<p>For the purpose of debugging the compiler, you may also specify a +name beginning with the ‘<samp>*</samp>’ character. Such a name is used only +for identifying the instruction in RTL dumps; it is equivalent to having +a nameless pattern for all other purposes. Names beginning with the +‘<samp>*</samp>’ character are not required to be unique. +</p> +<p>The name may also have the form ‘<samp>@<var>n</var></samp>’. This has the same +effect as a name ‘<samp><var>n</var></samp>’, but in addition tells the compiler to +generate further helper functions; see <a href="Parameterized-Names.html#Parameterized-Names">Parameterized Names</a> for details. +</p> +</li><li> The <em>RTL template</em>: This is a vector of incomplete RTL expressions +which describe the semantics of the instruction (see <a href="RTL-Template.html#RTL-Template">RTL Template</a>). +It is incomplete because it may contain <code>match_operand</code>, +<code>match_operator</code>, and <code>match_dup</code> expressions that stand for +operands of the instruction. + +<p>If the vector has multiple elements, the RTL template is treated as a +<code>parallel</code> expression. +</p> +</li><li> <a name="index-pattern-conditions"></a> +<a name="index-conditions_002c-in-patterns"></a> +The condition: This is a string which contains a C expression. When the +compiler attempts to match RTL against a pattern, the condition is +evaluated. If the condition evaluates to <code>true</code>, the match is +permitted. The condition may be an empty string, which is treated +as always <code>true</code>. + +<a name="index-named-patterns-and-conditions"></a> +<p>For a named pattern, the condition may not depend on the data in the +insn being matched, but only the target-machine-type flags. The compiler +needs to test these conditions during initialization in order to learn +exactly which named instructions are available in a particular run. +</p> +<a name="index-operands-1"></a> +<p>For nameless patterns, the condition is applied only when matching an +individual insn, and only after the insn has matched the pattern’s +recognition template. The insn’s operands may be found in the vector +<code>operands</code>. +</p> +<p>An instruction condition cannot become more restrictive as compilation +progresses. If the condition accepts a particular RTL instruction at +one stage of compilation, it must continue to accept that instruction +until the final pass. For example, ‘<samp>!reload_completed</samp>’ and +‘<samp>can_create_pseudo_p ()</samp>’ are both invalid instruction conditions, +because they are true during the earlier RTL passes and false during +the later ones. For the same reason, if a condition accepts an +instruction before register allocation, it cannot later try to control +register allocation by excluding certain register or value combinations. +</p> +<p>Although a condition cannot become more restrictive as compilation +progresses, the condition for a nameless pattern <em>can</em> become +more permissive. For example, a nameless instruction can require +‘<samp>reload_completed</samp>’ to be true, in which case it only matches +after register allocation. +</p> +</li><li> The <em>output template</em> or <em>output statement</em>: This is either +a string, or a fragment of C code which returns a string. + +<p>When simple substitution isn’t general enough, you can specify a piece +of C code to compute the output. See <a href="Output-Statement.html#Output-Statement">Output Statement</a>. +</p> +</li><li> The <em>insn attributes</em>: This is an optional vector containing the values of +attributes for insns matching this pattern (see <a href="Insn-Attributes.html#Insn-Attributes">Insn Attributes</a>). +</li></ol> + +<hr> +<div class="header"> +<p> +Next: <a href="Example.html#Example" accesskey="n" rel="next">Example</a>, Previous: <a href="Overview.html#Overview" accesskey="p" rel="previous">Overview</a>, Up: <a href="Machine-Desc.html#Machine-Desc" accesskey="u" rel="up">Machine Desc</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |