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diff --git a/share/doc/gccint/Calls.html b/share/doc/gccint/Calls.html new file mode 100644 index 0000000..90f1d05 --- /dev/null +++ b/share/doc/gccint/Calls.html @@ -0,0 +1,151 @@ +<!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: Calls</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Calls"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Calls"> +<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="RTL.html#RTL" rel="up" title="RTL"> +<link href="RTL-SSA.html#RTL-SSA" rel="next" title="RTL SSA"> +<link href="Insns.html#Insns" rel="previous" title="Insns"> +<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="Calls"></a> +<div class="header"> +<p> +Next: <a href="RTL-SSA.html#RTL-SSA" accesskey="n" rel="next">RTL SSA</a>, Previous: <a href="Insns.html#Insns" accesskey="p" rel="previous">Insns</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</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="RTL-Representation-of-Function_002dCall-Insns"></a> +<h3 class="section">14.20 RTL Representation of Function-Call Insns</h3> +<a name="index-calling-functions-in-RTL"></a> +<a name="index-RTL-function_002dcall-insns"></a> +<a name="index-function_002dcall-insns"></a> + +<p>Insns that call subroutines have the RTL expression code <code>call_insn</code>. +These insns must satisfy special rules, and their bodies must use a special +RTL expression code, <code>call</code>. +</p> +<a name="index-call-usage"></a> +<p>A <code>call</code> expression has two operands, as follows: +</p> +<div class="smallexample"> +<pre class="smallexample">(call (mem:<var>fm</var> <var>addr</var>) <var>nbytes</var>) +</pre></div> + +<p>Here <var>nbytes</var> is an operand that represents the number of bytes of +argument data being passed to the subroutine, <var>fm</var> is a machine mode +(which must equal as the definition of the <code>FUNCTION_MODE</code> macro in +the machine description) and <var>addr</var> represents the address of the +subroutine. +</p> +<p>For a subroutine that returns no value, the <code>call</code> expression as +shown above is the entire body of the insn, except that the insn might +also contain <code>use</code> or <code>clobber</code> expressions. +</p> +<a name="index-BLKmode_002c-and-function-return-values"></a> +<p>For a subroutine that returns a value whose mode is not <code>BLKmode</code>, +the value is returned in a hard register. If this register’s number is +<var>r</var>, then the body of the call insn looks like this: +</p> +<div class="smallexample"> +<pre class="smallexample">(set (reg:<var>m</var> <var>r</var>) + (call (mem:<var>fm</var> <var>addr</var>) <var>nbytes</var>)) +</pre></div> + +<p>This RTL expression makes it clear (to the optimizer passes) that the +appropriate register receives a useful value in this insn. +</p> +<p>When a subroutine returns a <code>BLKmode</code> value, it is handled by +passing to the subroutine the address of a place to store the value. +So the call insn itself does not “return” any value, and it has the +same RTL form as a call that returns nothing. +</p> +<p>On some machines, the call instruction itself clobbers some register, +for example to contain the return address. <code>call_insn</code> insns +on these machines should have a body which is a <code>parallel</code> +that contains both the <code>call</code> expression and <code>clobber</code> +expressions that indicate which registers are destroyed. Similarly, +if the call instruction requires some register other than the stack +pointer that is not explicitly mentioned in its RTL, a <code>use</code> +subexpression should mention that register. +</p> +<p>Functions that are called are assumed to modify all registers listed in +the configuration macro <code>CALL_USED_REGISTERS</code> (see <a href="Register-Basics.html#Register-Basics">Register Basics</a>) and, with the exception of <code>const</code> functions and library +calls, to modify all of memory. +</p> +<p>Insns containing just <code>use</code> expressions directly precede the +<code>call_insn</code> insn to indicate which registers contain inputs to the +function. Similarly, if registers other than those in +<code>CALL_USED_REGISTERS</code> are clobbered by the called function, insns +containing a single <code>clobber</code> follow immediately after the call to +indicate which registers. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="RTL-SSA.html#RTL-SSA" accesskey="n" rel="next">RTL SSA</a>, Previous: <a href="Insns.html#Insns" accesskey="p" rel="previous">Insns</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</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> |