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.
117 lines
5.4 KiB
HTML
117 lines
5.4 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Allocation Order - GNU Compiler Collection (GCC) Internals</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="GNU Compiler Collection (GCC) Internals">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="Registers.html#Registers" title="Registers">
|
|
<link rel="prev" href="Register-Basics.html#Register-Basics" title="Register Basics">
|
|
<link rel="next" href="Values-in-Registers.html#Values-in-Registers" title="Values in Registers">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
Copyright (C) 1988-2015 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.-->
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
|
<style type="text/css"><!--
|
|
pre.display { font-family:inherit }
|
|
pre.format { font-family:inherit }
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
|
pre.smallexample { font-size:smaller }
|
|
pre.smalllisp { font-size:smaller }
|
|
span.sc { font-variant:small-caps }
|
|
span.roman { font-family:serif; font-weight:normal; }
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
|
--></style>
|
|
</head>
|
|
<body>
|
|
<div class="node">
|
|
<a name="Allocation-Order"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="Values-in-Registers.html#Values-in-Registers">Values in Registers</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="Register-Basics.html#Register-Basics">Register Basics</a>,
|
|
Up: <a rel="up" accesskey="u" href="Registers.html#Registers">Registers</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h4 class="subsection">17.7.2 Order of Allocation of Registers</h4>
|
|
|
|
<p><a name="index-order-of-register-allocation-4072"></a><a name="index-register-allocation-order-4073"></a>
|
|
<!-- prevent bad page break with this line -->
|
|
Registers are allocated in order.
|
|
|
|
<div class="defun">
|
|
— Macro: <b>REG_ALLOC_ORDER</b><var><a name="index-REG_005fALLOC_005fORDER-4074"></a></var><br>
|
|
<blockquote><p>If defined, an initializer for a vector of integers, containing the
|
|
numbers of hard registers in the order in which GCC should prefer
|
|
to use them (from most preferred to least).
|
|
|
|
<p>If this macro is not defined, registers are used lowest numbered first
|
|
(all else being equal).
|
|
|
|
<p>One use of this macro is on machines where the highest numbered
|
|
registers must always be saved and the save-multiple-registers
|
|
instruction supports only sequences of consecutive registers. On such
|
|
machines, define <code>REG_ALLOC_ORDER</code> to be an initializer that lists
|
|
the highest numbered allocable register first.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>ADJUST_REG_ALLOC_ORDER</b><var><a name="index-ADJUST_005fREG_005fALLOC_005fORDER-4075"></a></var><br>
|
|
<blockquote><p>A C statement (sans semicolon) to choose the order in which to allocate
|
|
hard registers for pseudo-registers local to a basic block.
|
|
|
|
<p>Store the desired register order in the array <code>reg_alloc_order</code>.
|
|
Element 0 should be the register to allocate first; element 1, the next
|
|
register; and so on.
|
|
|
|
<p>The macro body should not assume anything about the contents of
|
|
<code>reg_alloc_order</code> before execution of the macro.
|
|
|
|
<p>On most machines, it is not necessary to define this macro.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>HONOR_REG_ALLOC_ORDER</b><var><a name="index-HONOR_005fREG_005fALLOC_005fORDER-4076"></a></var><br>
|
|
<blockquote><p>Normally, IRA tries to estimate the costs for saving a register in the
|
|
prologue and restoring it in the epilogue. This discourages it from
|
|
using call-saved registers. If a machine wants to ensure that IRA
|
|
allocates registers in the order given by REG_ALLOC_ORDER even if some
|
|
call-saved registers appear earlier than call-used ones, then define this
|
|
macro as a C expression to nonzero. Default is 0.
|
|
</p></blockquote></div>
|
|
|
|
<div class="defun">
|
|
— Macro: <b>IRA_HARD_REGNO_ADD_COST_MULTIPLIER</b> (<var>regno</var>)<var><a name="index-IRA_005fHARD_005fREGNO_005fADD_005fCOST_005fMULTIPLIER-4077"></a></var><br>
|
|
<blockquote><p>In some case register allocation order is not enough for the
|
|
Integrated Register Allocator (<acronym>IRA</acronym>) to generate a good code.
|
|
If this macro is defined, it should return a floating point value
|
|
based on <var>regno</var>. The cost of using <var>regno</var> for a pseudo will
|
|
be increased by approximately the pseudo's usage frequency times the
|
|
value returned by this macro. Not defining this macro is equivalent
|
|
to having it always return <code>0.0</code>.
|
|
|
|
<p>On most machines, it is not necessary to define this macro.
|
|
</p></blockquote></div>
|
|
|
|
</body></html>
|
|
|