You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
297 lines
12 KiB
HTML
297 lines
12 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2018 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 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Tuple representation (GNU Compiler Collection (GCC) Internals)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Tuple representation (GNU Compiler Collection (GCC) Internals)">
|
||
|
|
<meta name="keywords" content="Tuple representation (GNU Compiler Collection (GCC) Internals)">
|
||
|
|
<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="GIMPLE.html#GIMPLE" rel="up" title="GIMPLE">
|
||
|
|
<link href="Class-hierarchy-of-GIMPLE-statements.html#Class-hierarchy-of-GIMPLE-statements" rel="next" title="Class hierarchy of GIMPLE statements">
|
||
|
|
<link href="GIMPLE.html#GIMPLE" rel="prev" title="GIMPLE">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
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.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Tuple-representation"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Class-hierarchy-of-GIMPLE-statements.html#Class-hierarchy-of-GIMPLE-statements" accesskey="n" rel="next">Class hierarchy of GIMPLE statements</a>, Up: <a href="GIMPLE.html#GIMPLE" accesskey="u" rel="up">GIMPLE</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="Tuple-representation-1"></a>
|
||
|
|
<h3 class="section">12.1 Tuple representation</h3>
|
||
|
|
<a name="index-tuples"></a>
|
||
|
|
|
||
|
|
<p>GIMPLE instructions are tuples of variable size divided in two
|
||
|
|
groups: a header describing the instruction and its locations,
|
||
|
|
and a variable length body with all the operands. Tuples are
|
||
|
|
organized into a hierarchy with 3 main classes of tuples.
|
||
|
|
</p>
|
||
|
|
<a name="gimple-_0028gsbase_0029"></a>
|
||
|
|
<h4 class="subsection">12.1.1 <code>gimple</code> (gsbase)</h4>
|
||
|
|
<a name="index-gimple"></a>
|
||
|
|
|
||
|
|
<p>This is the root of the hierarchy, it holds basic information
|
||
|
|
needed by most GIMPLE statements. There are some fields that
|
||
|
|
may not be relevant to every GIMPLE statement, but those were
|
||
|
|
moved into the base structure to take advantage of holes left by
|
||
|
|
other fields (thus making the structure more compact). The
|
||
|
|
structure takes 4 words (32 bytes) on 64 bit hosts:
|
||
|
|
</p>
|
||
|
|
<table>
|
||
|
|
<tr><td>Field</td><td>Size (bits)</td></tr>
|
||
|
|
<tr><td><code>code</code></td><td>8</td></tr>
|
||
|
|
<tr><td><code>subcode</code></td><td>16</td></tr>
|
||
|
|
<tr><td><code>no_warning</code></td><td>1</td></tr>
|
||
|
|
<tr><td><code>visited</code></td><td>1</td></tr>
|
||
|
|
<tr><td><code>nontemporal_move</code></td><td>1</td></tr>
|
||
|
|
<tr><td><code>plf</code></td><td>2</td></tr>
|
||
|
|
<tr><td><code>modified</code></td><td>1</td></tr>
|
||
|
|
<tr><td><code>has_volatile_ops</code></td><td>1</td></tr>
|
||
|
|
<tr><td><code>references_memory_p</code></td><td>1</td></tr>
|
||
|
|
<tr><td><code>uid</code></td><td>32</td></tr>
|
||
|
|
<tr><td><code>location</code></td><td>32</td></tr>
|
||
|
|
<tr><td><code>num_ops</code></td><td>32</td></tr>
|
||
|
|
<tr><td><code>bb</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>block</code></td><td>63</td></tr>
|
||
|
|
<tr><td>Total size</td><td>32 bytes</td></tr>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li> <code>code</code>
|
||
|
|
Main identifier for a GIMPLE instruction.
|
||
|
|
|
||
|
|
</li><li> <code>subcode</code>
|
||
|
|
Used to distinguish different variants of the same basic
|
||
|
|
instruction or provide flags applicable to a given code. The
|
||
|
|
<code>subcode</code> flags field has different uses depending on the code of
|
||
|
|
the instruction, but mostly it distinguishes instructions of the
|
||
|
|
same family. The most prominent use of this field is in
|
||
|
|
assignments, where subcode indicates the operation done on the
|
||
|
|
RHS of the assignment. For example, a = b + c is encoded as
|
||
|
|
<code>GIMPLE_ASSIGN <PLUS_EXPR, a, b, c></code>.
|
||
|
|
|
||
|
|
</li><li> <code>no_warning</code>
|
||
|
|
Bitflag to indicate whether a warning has already been issued on
|
||
|
|
this statement.
|
||
|
|
|
||
|
|
</li><li> <code>visited</code>
|
||
|
|
General purpose “visited” marker. Set and cleared by each pass
|
||
|
|
when needed.
|
||
|
|
|
||
|
|
</li><li> <code>nontemporal_move</code>
|
||
|
|
Bitflag used in assignments that represent non-temporal moves.
|
||
|
|
Although this bitflag is only used in assignments, it was moved
|
||
|
|
into the base to take advantage of the bit holes left by the
|
||
|
|
previous fields.
|
||
|
|
|
||
|
|
</li><li> <code>plf</code>
|
||
|
|
Pass Local Flags. This 2-bit mask can be used as general purpose
|
||
|
|
markers by any pass. Passes are responsible for clearing and
|
||
|
|
setting these two flags accordingly.
|
||
|
|
|
||
|
|
</li><li> <code>modified</code>
|
||
|
|
Bitflag to indicate whether the statement has been modified.
|
||
|
|
Used mainly by the operand scanner to determine when to re-scan a
|
||
|
|
statement for operands.
|
||
|
|
|
||
|
|
</li><li> <code>has_volatile_ops</code>
|
||
|
|
Bitflag to indicate whether this statement contains operands that
|
||
|
|
have been marked volatile.
|
||
|
|
|
||
|
|
</li><li> <code>references_memory_p</code>
|
||
|
|
Bitflag to indicate whether this statement contains memory
|
||
|
|
references (i.e., its operands are either global variables, or
|
||
|
|
pointer dereferences or anything that must reside in memory).
|
||
|
|
|
||
|
|
</li><li> <code>uid</code>
|
||
|
|
This is an unsigned integer used by passes that want to assign
|
||
|
|
IDs to every statement. These IDs must be assigned and used by
|
||
|
|
each pass.
|
||
|
|
|
||
|
|
</li><li> <code>location</code>
|
||
|
|
This is a <code>location_t</code> identifier to specify source code
|
||
|
|
location for this statement. It is inherited from the front
|
||
|
|
end.
|
||
|
|
|
||
|
|
</li><li> <code>num_ops</code>
|
||
|
|
Number of operands that this statement has. This specifies the
|
||
|
|
size of the operand vector embedded in the tuple. Only used in
|
||
|
|
some tuples, but it is declared in the base tuple to take
|
||
|
|
advantage of the 32-bit hole left by the previous fields.
|
||
|
|
|
||
|
|
</li><li> <code>bb</code>
|
||
|
|
Basic block holding the instruction.
|
||
|
|
|
||
|
|
</li><li> <code>block</code>
|
||
|
|
Lexical block holding this statement. Also used for debug
|
||
|
|
information generation.
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<a name="gimple_005fstatement_005fwith_005fops"></a>
|
||
|
|
<h4 class="subsection">12.1.2 <code>gimple_statement_with_ops</code></h4>
|
||
|
|
<a name="index-gimple_005fstatement_005fwith_005fops"></a>
|
||
|
|
|
||
|
|
<p>This tuple is actually split in two:
|
||
|
|
<code>gimple_statement_with_ops_base</code> and
|
||
|
|
<code>gimple_statement_with_ops</code>. This is needed to accommodate the
|
||
|
|
way the operand vector is allocated. The operand vector is
|
||
|
|
defined to be an array of 1 element. So, to allocate a dynamic
|
||
|
|
number of operands, the memory allocator (<code>gimple_alloc</code>) simply
|
||
|
|
allocates enough memory to hold the structure itself plus <code>N
|
||
|
|
- 1</code> operands which run “off the end” of the structure. For
|
||
|
|
example, to allocate space for a tuple with 3 operands,
|
||
|
|
<code>gimple_alloc</code> reserves <code>sizeof (struct
|
||
|
|
gimple_statement_with_ops) + 2 * sizeof (tree)</code> bytes.
|
||
|
|
</p>
|
||
|
|
<p>On the other hand, several fields in this tuple need to be shared
|
||
|
|
with the <code>gimple_statement_with_memory_ops</code> tuple. So, these
|
||
|
|
common fields are placed in <code>gimple_statement_with_ops_base</code> which
|
||
|
|
is then inherited from the other two tuples.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<table>
|
||
|
|
<tr><td><code>gsbase</code></td><td>256</td></tr>
|
||
|
|
<tr><td><code>def_ops</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>use_ops</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>op</code></td><td><code>num_ops</code> * 64</td></tr>
|
||
|
|
<tr><td>Total size</td><td>48 + 8 * <code>num_ops</code> bytes</td></tr>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li> <code>gsbase</code>
|
||
|
|
Inherited from <code>struct gimple</code>.
|
||
|
|
|
||
|
|
</li><li> <code>def_ops</code>
|
||
|
|
Array of pointers into the operand array indicating all the slots that
|
||
|
|
contain a variable written-to by the statement. This array is
|
||
|
|
also used for immediate use chaining. Note that it would be
|
||
|
|
possible to not rely on this array, but the changes required to
|
||
|
|
implement this are pretty invasive.
|
||
|
|
|
||
|
|
</li><li> <code>use_ops</code>
|
||
|
|
Similar to <code>def_ops</code> but for variables read by the statement.
|
||
|
|
|
||
|
|
</li><li> <code>op</code>
|
||
|
|
Array of trees with <code>num_ops</code> slots.
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<a name="gimple_005fstatement_005fwith_005fmemory_005fops"></a>
|
||
|
|
<h4 class="subsection">12.1.3 <code>gimple_statement_with_memory_ops</code></h4>
|
||
|
|
|
||
|
|
<p>This tuple is essentially identical to <code>gimple_statement_with_ops</code>,
|
||
|
|
except that it contains 4 additional fields to hold vectors
|
||
|
|
related memory stores and loads. Similar to the previous case,
|
||
|
|
the structure is split in two to accommodate for the operand
|
||
|
|
vector (<code>gimple_statement_with_memory_ops_base</code> and
|
||
|
|
<code>gimple_statement_with_memory_ops</code>).
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<table>
|
||
|
|
<tr><td>Field</td><td>Size (bits)</td></tr>
|
||
|
|
<tr><td><code>gsbase</code></td><td>256</td></tr>
|
||
|
|
<tr><td><code>def_ops</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>use_ops</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>vdef_ops</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>vuse_ops</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>stores</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>loads</code></td><td>64</td></tr>
|
||
|
|
<tr><td><code>op</code></td><td><code>num_ops</code> * 64</td></tr>
|
||
|
|
<tr><td>Total size</td><td>80 + 8 * <code>num_ops</code> bytes</td></tr>
|
||
|
|
</table>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li> <code>vdef_ops</code>
|
||
|
|
Similar to <code>def_ops</code> but for <code>VDEF</code> operators. There is
|
||
|
|
one entry per memory symbol written by this statement. This is
|
||
|
|
used to maintain the memory SSA use-def and def-def chains.
|
||
|
|
|
||
|
|
</li><li> <code>vuse_ops</code>
|
||
|
|
Similar to <code>use_ops</code> but for <code>VUSE</code> operators. There is
|
||
|
|
one entry per memory symbol loaded by this statement. This is
|
||
|
|
used to maintain the memory SSA use-def chains.
|
||
|
|
|
||
|
|
</li><li> <code>stores</code>
|
||
|
|
Bitset with all the UIDs for the symbols written-to by the
|
||
|
|
statement. This is different than <code>vdef_ops</code> in that all the
|
||
|
|
affected symbols are mentioned in this set. If memory
|
||
|
|
partitioning is enabled, the <code>vdef_ops</code> vector will refer to memory
|
||
|
|
partitions. Furthermore, no SSA information is stored in this
|
||
|
|
set.
|
||
|
|
|
||
|
|
</li><li> <code>loads</code>
|
||
|
|
Similar to <code>stores</code>, but for memory loads. (Note that there
|
||
|
|
is some amount of redundancy here, it should be possible to
|
||
|
|
reduce memory utilization further by removing these sets).
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<p>All the other tuples are defined in terms of these three basic
|
||
|
|
ones. Each tuple will add some fields.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Class-hierarchy-of-GIMPLE-statements.html#Class-hierarchy-of-GIMPLE-statements" accesskey="n" rel="next">Class hierarchy of GIMPLE statements</a>, Up: <a href="GIMPLE.html#GIMPLE" accesskey="u" rel="up">GIMPLE</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>
|