diff options
| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
|---|---|---|
| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gccint/Mode-Switching.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
Diffstat (limited to 'share/doc/gccint/Mode-Switching.html')
| -rw-r--r-- | share/doc/gccint/Mode-Switching.html | 183 |
1 files changed, 183 insertions, 0 deletions
diff --git a/share/doc/gccint/Mode-Switching.html b/share/doc/gccint/Mode-Switching.html new file mode 100644 index 0000000..d22e6a7 --- /dev/null +++ b/share/doc/gccint/Mode-Switching.html @@ -0,0 +1,183 @@ +<!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: Mode Switching</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Mode Switching"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Mode Switching"> +<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="Target-Macros.html#Target-Macros" rel="up" title="Target Macros"> +<link href="Target-Attributes.html#Target-Attributes" rel="next" title="Target Attributes"> +<link href="Floating-Point.html#Floating-Point" rel="previous" title="Floating Point"> +<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="Mode-Switching"></a> +<div class="header"> +<p> +Next: <a href="Target-Attributes.html#Target-Attributes" accesskey="n" rel="next">Target Attributes</a>, Previous: <a href="Floating-Point.html#Floating-Point" accesskey="p" rel="previous">Floating Point</a>, Up: <a href="Target-Macros.html#Target-Macros" accesskey="u" rel="up">Target Macros</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="Mode-Switching-Instructions"></a> +<h3 class="section">18.23 Mode Switching Instructions</h3> +<a name="index-mode-switching"></a> +<p>The following macros control mode switching optimizations: +</p> +<dl> +<dt><a name="index-OPTIMIZE_005fMODE_005fSWITCHING"></a>Macro: <strong>OPTIMIZE_MODE_SWITCHING</strong> <em>(<var>entity</var>)</em></dt> +<dd><p>Define this macro if the port needs extra instructions inserted for mode +switching in an optimizing compilation. +</p> +<p>For an example, the SH4 can perform both single and double precision +floating point operations, but to perform a single precision operation, +the FPSCR PR bit has to be cleared, while for a double precision +operation, this bit has to be set. Changing the PR bit requires a general +purpose register as a scratch register, hence these FPSCR sets have to +be inserted before reload, i.e. you cannot put this into instruction emitting +or <code>TARGET_MACHINE_DEPENDENT_REORG</code>. +</p> +<p>You can have multiple entities that are mode-switched, and select at run time +which entities actually need it. <code>OPTIMIZE_MODE_SWITCHING</code> should +return nonzero for any <var>entity</var> that needs mode-switching. +If you define this macro, you also have to define +<code>NUM_MODES_FOR_MODE_SWITCHING</code>, <code>TARGET_MODE_NEEDED</code>, +<code>TARGET_MODE_PRIORITY</code> and <code>TARGET_MODE_EMIT</code>. +<code>TARGET_MODE_AFTER</code>, <code>TARGET_MODE_ENTRY</code>, and <code>TARGET_MODE_EXIT</code> +are optional. +</p></dd></dl> + +<dl> +<dt><a name="index-NUM_005fMODES_005fFOR_005fMODE_005fSWITCHING"></a>Macro: <strong>NUM_MODES_FOR_MODE_SWITCHING</strong></dt> +<dd><p>If you define <code>OPTIMIZE_MODE_SWITCHING</code>, you have to define this as +initializer for an array of integers. Each initializer element +N refers to an entity that needs mode switching, and specifies the number +of different modes that might need to be set for this entity. +The position of the initializer in the initializer—starting counting at +zero—determines the integer that is used to refer to the mode-switched +entity in question. +In macros that take mode arguments / yield a mode result, modes are +represented as numbers 0 … N - 1. N is used to specify that no mode +switch is needed / supplied. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fMODE_005fEMIT"></a>Target Hook: <em>void</em> <strong>TARGET_MODE_EMIT</strong> <em>(int <var>entity</var>, int <var>mode</var>, int <var>prev_mode</var>, HARD_REG_SET <var>regs_live</var>)</em></dt> +<dd><p>Generate one or more insns to set <var>entity</var> to <var>mode</var>. +<var>hard_reg_live</var> is the set of hard registers live at the point where +the insn(s) are to be inserted. <var>prev_moxde</var> indicates the mode +to switch from. Sets of a lower numbered entity will be emitted before +sets of a higher numbered entity to a mode of the same or lower priority. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fMODE_005fNEEDED"></a>Target Hook: <em>int</em> <strong>TARGET_MODE_NEEDED</strong> <em>(int <var>entity</var>, rtx_insn *<var>insn</var>)</em></dt> +<dd><p><var>entity</var> is an integer specifying a mode-switched entity. +If <code>OPTIMIZE_MODE_SWITCHING</code> is defined, you must define this macro +to return an integer value not larger than the corresponding element +in <code>NUM_MODES_FOR_MODE_SWITCHING</code>, to denote the mode that <var>entity</var> +must be switched into prior to the execution of <var>insn</var>. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fMODE_005fAFTER"></a>Target Hook: <em>int</em> <strong>TARGET_MODE_AFTER</strong> <em>(int <var>entity</var>, int <var>mode</var>, rtx_insn *<var>insn</var>)</em></dt> +<dd><p><var>entity</var> is an integer specifying a mode-switched entity. +If this macro is defined, it is evaluated for every <var>insn</var> during mode +switching. It determines the mode that an insn results +in (if different from the incoming mode). +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fMODE_005fENTRY"></a>Target Hook: <em>int</em> <strong>TARGET_MODE_ENTRY</strong> <em>(int <var>entity</var>)</em></dt> +<dd><p>If this macro is defined, it is evaluated for every <var>entity</var> that +needs mode switching. It should evaluate to an integer, which is a mode +that <var>entity</var> is assumed to be switched to at function entry. +If <code>TARGET_MODE_ENTRY</code> is defined then <code>TARGET_MODE_EXIT</code> +must be defined. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fMODE_005fEXIT"></a>Target Hook: <em>int</em> <strong>TARGET_MODE_EXIT</strong> <em>(int <var>entity</var>)</em></dt> +<dd><p>If this macro is defined, it is evaluated for every <var>entity</var> that +needs mode switching. It should evaluate to an integer, which is a mode +that <var>entity</var> is assumed to be switched to at function exit. +If <code>TARGET_MODE_EXIT</code> is defined then <code>TARGET_MODE_ENTRY</code> +must be defined. +</p></dd></dl> + +<dl> +<dt><a name="index-TARGET_005fMODE_005fPRIORITY"></a>Target Hook: <em>int</em> <strong>TARGET_MODE_PRIORITY</strong> <em>(int <var>entity</var>, int <var>n</var>)</em></dt> +<dd><p>This macro specifies the order in which modes for <var>entity</var> +are processed. 0 is the highest priority, +<code>NUM_MODES_FOR_MODE_SWITCHING[<var>entity</var>] - 1</code> the lowest. +The value of the macro should be an integer designating a mode +for <var>entity</var>. For any fixed <var>entity</var>, <code>mode_priority</code> +(<var>entity</var>, <var>n</var>) shall be a bijection in 0 … +<code>num_modes_for_mode_switching[<var>entity</var>] - 1</code>. +</p></dd></dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Target-Attributes.html#Target-Attributes" accesskey="n" rel="next">Target Attributes</a>, Previous: <a href="Floating-Point.html#Floating-Point" accesskey="p" rel="previous">Floating Point</a>, Up: <a href="Target-Macros.html#Target-Macros" accesskey="u" rel="up">Target Macros</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> |