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diff --git a/share/doc/gccint/Parsing-pass.html b/share/doc/gccint/Parsing-pass.html new file mode 100644 index 0000000..b1a0e9c --- /dev/null +++ b/share/doc/gccint/Parsing-pass.html @@ -0,0 +1,164 @@ +<!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). 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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: Parsing pass</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Parsing pass"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Parsing pass"> +<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="Passes.html#Passes" rel="up" title="Passes"> +<link href="Gimplification-pass.html#Gimplification-pass" rel="next" title="Gimplification pass"> +<link href="Passes.html#Passes" rel="previous" title="Passes"> +<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="Parsing-pass"></a> +<div class="header"> +<p> +Next: <a href="Gimplification-pass.html#Gimplification-pass" accesskey="n" rel="next">Gimplification pass</a>, Up: <a href="Passes.html#Passes" accesskey="u" rel="up">Passes</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="Parsing-pass-1"></a> +<h3 class="section">9.1 Parsing pass</h3> +<a name="index-GENERIC"></a> +<a name="index-lang_005fhooks_002eparse_005ffile"></a> +<p>The language front end is invoked only once, via +<code>lang_hooks.parse_file</code>, to parse the entire input. The language +front end may use any intermediate language representation deemed +appropriate. The C front end uses GENERIC trees (see <a href="GENERIC.html#GENERIC">GENERIC</a>), plus +a double handful of language specific tree codes defined in +<samp>c-common.def</samp>. The Fortran front end uses a completely different +private representation. +</p> +<a name="index-GIMPLE"></a> +<a name="index-gimplification"></a> +<a name="index-gimplifier"></a> +<a name="index-language_002dindependent-intermediate-representation"></a> +<a name="index-intermediate-representation-lowering"></a> +<a name="index-lowering_002c-language_002ddependent-intermediate-representation"></a> +<p>At some point the front end must translate the representation used in the +front end to a representation understood by the language-independent +portions of the compiler. Current practice takes one of two forms. +The C front end manually invokes the gimplifier (see <a href="GIMPLE.html#GIMPLE">GIMPLE</a>) on each function, +and uses the gimplifier callbacks to convert the language-specific tree +nodes directly to GIMPLE before passing the function off to be compiled. +The Fortran front end converts from a private representation to GENERIC, +which is later lowered to GIMPLE when the function is compiled. Which +route to choose probably depends on how well GENERIC (plus extensions) +can be made to match up with the source language and necessary parsing +data structures. +</p> +<p>BUG: Gimplification must occur before nested function lowering, +and nested function lowering must be done by the front end before +passing the data off to cgraph. +</p> +<p>TODO: Cgraph should control nested function lowering. It would +only be invoked when it is certain that the outer-most function +is used. +</p> +<p>TODO: Cgraph needs a gimplify_function callback. It should be +invoked when (1) it is certain that the function is used, (2) +warning flags specified by the user require some amount of +compilation in order to honor, (3) the language indicates that +semantic analysis is not complete until gimplification occurs. +Hum… this sounds overly complicated. Perhaps we should just +have the front end gimplify always; in most cases it’s only one +function call. +</p> +<p>The front end needs to pass all function definitions and top level +declarations off to the middle-end so that they can be compiled and +emitted to the object file. For a simple procedural language, it is +usually most convenient to do this as each top level declaration or +definition is seen. There is also a distinction to be made between +generating functional code and generating complete debug information. +The only thing that is absolutely required for functional code is that +function and data <em>definitions</em> be passed to the middle-end. For +complete debug information, function, data and type declarations +should all be passed as well. +</p> +<a name="index-rest_005fof_005fdecl_005fcompilation"></a> +<a name="index-rest_005fof_005ftype_005fcompilation"></a> +<a name="index-cgraph_005ffinalize_005ffunction"></a> +<p>In any case, the front end needs each complete top-level function or +data declaration, and each data definition should be passed to +<code>rest_of_decl_compilation</code>. Each complete type definition should +be passed to <code>rest_of_type_compilation</code>. Each function definition +should be passed to <code>cgraph_finalize_function</code>. +</p> +<p>TODO: I know rest_of_compilation currently has all sorts of +RTL generation semantics. I plan to move all code generation +bits (both Tree and RTL) to compile_function. Should we hide +cgraph from the front ends and move back to rest_of_compilation +as the official interface? Possibly we should rename all three +interfaces such that the names match in some meaningful way and +that is more descriptive than "rest_of". +</p> +<p>The middle-end will, at its option, emit the function and data +definitions immediately or queue them for later processing. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Gimplification-pass.html#Gimplification-pass" accesskey="n" rel="next">Gimplification pass</a>, Up: <a href="Passes.html#Passes" accesskey="u" rel="up">Passes</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> |