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diff --git a/share/doc/gcc/PowerPC-Hardware-Transactional-Memory-Built_002din-Functions.html b/share/doc/gcc/PowerPC-Hardware-Transactional-Memory-Built_002din-Functions.html new file mode 100644 index 0000000..654ab0c --- /dev/null +++ b/share/doc/gcc/PowerPC-Hardware-Transactional-Memory-Built_002din-Functions.html @@ -0,0 +1,307 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This file documents the use of the GNU compilers. + +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>Using the GNU Compiler Collection (GCC): PowerPC Hardware Transactional Memory Built-in Functions</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): PowerPC Hardware Transactional Memory Built-in Functions"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): PowerPC Hardware Transactional Memory Built-in Functions"> +<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="Indices.html#Indices" rel="index" title="Indices"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Target-Builtins.html#Target-Builtins" rel="up" title="Target Builtins"> +<link href="PowerPC-Atomic-Memory-Operation-Functions.html#PowerPC-Atomic-Memory-Operation-Functions" rel="next" title="PowerPC Atomic Memory Operation Functions"> +<link href="PowerPC-AltiVec-Built_002din-Functions-Available-on-ISA-3_002e1.html#PowerPC-AltiVec-Built_002din-Functions-Available-on-ISA-3_002e1" rel="previous" title="PowerPC AltiVec Built-in Functions Available on ISA 3.1"> +<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_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="PowerPC-Hardware-Transactional-Memory-Built_002din-Functions"></a> +<div class="header"> +<p> +Next: <a href="PowerPC-Atomic-Memory-Operation-Functions.html#PowerPC-Atomic-Memory-Operation-Functions" accesskey="n" rel="next">PowerPC Atomic Memory Operation Functions</a>, Previous: <a href="PowerPC-AltiVec_002fVSX-Built_002din-Functions.html#PowerPC-AltiVec_002fVSX-Built_002din-Functions" accesskey="p" rel="previous">PowerPC AltiVec/VSX Built-in Functions</a>, Up: <a href="Target-Builtins.html#Target-Builtins" accesskey="u" rel="up">Target Builtins</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="PowerPC-Hardware-Transactional-Memory-Built_002din-Functions-1"></a> +<h4 class="subsection">6.60.24 PowerPC Hardware Transactional Memory Built-in Functions</h4> +<p>GCC provides two interfaces for accessing the Hardware Transactional +Memory (HTM) instructions available on some of the PowerPC family +of processors (eg, POWER8). The two interfaces come in a low level +interface, consisting of built-in functions specific to PowerPC and a +higher level interface consisting of inline functions that are common +between PowerPC and S/390. +</p> +<a name="PowerPC-HTM-Low-Level-Built_002din-Functions"></a> +<h4 class="subsubsection">6.60.24.1 PowerPC HTM Low Level Built-in Functions</h4> + +<p>The following low level built-in functions are available with +<samp>-mhtm</samp> or <samp>-mcpu=CPU</samp> where CPU is ‘power8’ or later. +They all generate the machine instruction that is part of the name. +</p> +<p>The HTM builtins (with the exception of <code>__builtin_tbegin</code>) return +the full 4-bit condition register value set by their associated hardware +instruction. The header file <code>htmintrin.h</code> defines some macros that can +be used to decipher the return value. The <code>__builtin_tbegin</code> builtin +returns a simple <code>true</code> or <code>false</code> value depending on whether a transaction was +successfully started or not. The arguments of the builtins match exactly the +type and order of the associated hardware instruction’s operands, except for +the <code>__builtin_tcheck</code> builtin, which does not take any input arguments. +Refer to the ISA manual for a description of each instruction’s operands. +</p> +<div class="smallexample"> +<pre class="smallexample">unsigned int __builtin_tbegin (unsigned int); +unsigned int __builtin_tend (unsigned int); + +unsigned int __builtin_tabort (unsigned int); +unsigned int __builtin_tabortdc (unsigned int, unsigned int, unsigned int); +unsigned int __builtin_tabortdci (unsigned int, unsigned int, int); +unsigned int __builtin_tabortwc (unsigned int, unsigned int, unsigned int); +unsigned int __builtin_tabortwci (unsigned int, unsigned int, int); + +unsigned int __builtin_tcheck (void); +unsigned int __builtin_treclaim (unsigned int); +unsigned int __builtin_trechkpt (void); +unsigned int __builtin_tsr (unsigned int); +</pre></div> + +<p>In addition to the above HTM built-ins, we have added built-ins for +some common extended mnemonics of the HTM instructions: +</p> +<div class="smallexample"> +<pre class="smallexample">unsigned int __builtin_tendall (void); +unsigned int __builtin_tresume (void); +unsigned int __builtin_tsuspend (void); +</pre></div> + +<p>Note that the semantics of the above HTM builtins are required to mimic +the locking semantics used for critical sections. Builtins that are used +to create a new transaction or restart a suspended transaction must have +lock acquisition like semantics while those builtins that end or suspend a +transaction must have lock release like semantics. Specifically, this must +mimic lock semantics as specified by C++11, for example: Lock acquisition is +as-if an execution of __atomic_exchange_n(&globallock,1,__ATOMIC_ACQUIRE) +that returns 0, and lock release is as-if an execution of +__atomic_store(&globallock,0,__ATOMIC_RELEASE), with globallock being an +implicit implementation-defined lock used for all transactions. The HTM +instructions associated with with the builtins inherently provide the +correct acquisition and release hardware barriers required. However, +the compiler must also be prohibited from moving loads and stores across +the builtins in a way that would violate their semantics. This has been +accomplished by adding memory barriers to the associated HTM instructions +(which is a conservative approach to provide acquire and release semantics). +Earlier versions of the compiler did not treat the HTM instructions as +memory barriers. A <code>__TM_FENCE__</code> macro has been added, which can +be used to determine whether the current compiler treats HTM instructions +as memory barriers or not. This allows the user to explicitly add memory +barriers to their code when using an older version of the compiler. +</p> +<p>The following set of built-in functions are available to gain access +to the HTM specific special purpose registers. +</p> +<div class="smallexample"> +<pre class="smallexample">unsigned long __builtin_get_texasr (void); +unsigned long __builtin_get_texasru (void); +unsigned long __builtin_get_tfhar (void); +unsigned long __builtin_get_tfiar (void); + +void __builtin_set_texasr (unsigned long); +void __builtin_set_texasru (unsigned long); +void __builtin_set_tfhar (unsigned long); +void __builtin_set_tfiar (unsigned long); +</pre></div> + +<p>Example usage of these low level built-in functions may look like: +</p> +<div class="smallexample"> +<pre class="smallexample">#include <htmintrin.h> + +int num_retries = 10; + +while (1) + { + if (__builtin_tbegin (0)) + { + /* Transaction State Initiated. */ + if (is_locked (lock)) + __builtin_tabort (0); + ... transaction code... + __builtin_tend (0); + break; + } + else + { + /* Transaction State Failed. Use locks if the transaction + failure is "persistent" or we've tried too many times. */ + if (num_retries-- <= 0 + || _TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ())) + { + acquire_lock (lock); + ... non transactional fallback path... + release_lock (lock); + break; + } + } + } +</pre></div> + +<p>One final built-in function has been added that returns the value of +the 2-bit Transaction State field of the Machine Status Register (MSR) +as stored in <code>CR0</code>. +</p> +<div class="smallexample"> +<pre class="smallexample">unsigned long __builtin_ttest (void) +</pre></div> + +<p>This built-in can be used to determine the current transaction state +using the following code example: +</p> +<div class="smallexample"> +<pre class="smallexample">#include <htmintrin.h> + +unsigned char tx_state = _HTM_STATE (__builtin_ttest ()); + +if (tx_state == _HTM_TRANSACTIONAL) + { + /* Code to use in transactional state. */ + } +else if (tx_state == _HTM_NONTRANSACTIONAL) + { + /* Code to use in non-transactional state. */ + } +else if (tx_state == _HTM_SUSPENDED) + { + /* Code to use in transaction suspended state. */ + } +</pre></div> + +<a name="PowerPC-HTM-High-Level-Inline-Functions"></a> +<h4 class="subsubsection">6.60.24.2 PowerPC HTM High Level Inline Functions</h4> + +<p>The following high level HTM interface is made available by including +<code><htmxlintrin.h></code> and using <samp>-mhtm</samp> or <samp>-mcpu=CPU</samp> +where CPU is ‘power8’ or later. This interface is common between PowerPC +and S/390, allowing users to write one HTM source implementation that +can be compiled and executed on either system. +</p> +<div class="smallexample"> +<pre class="smallexample">long __TM_simple_begin (void); +long __TM_begin (void* const TM_buff); +long __TM_end (void); +void __TM_abort (void); +void __TM_named_abort (unsigned char const code); +void __TM_resume (void); +void __TM_suspend (void); + +long __TM_is_user_abort (void* const TM_buff); +long __TM_is_named_user_abort (void* const TM_buff, unsigned char *code); +long __TM_is_illegal (void* const TM_buff); +long __TM_is_footprint_exceeded (void* const TM_buff); +long __TM_nesting_depth (void* const TM_buff); +long __TM_is_nested_too_deep(void* const TM_buff); +long __TM_is_conflict(void* const TM_buff); +long __TM_is_failure_persistent(void* const TM_buff); +long __TM_failure_address(void* const TM_buff); +long long __TM_failure_code(void* const TM_buff); +</pre></div> + +<p>Using these common set of HTM inline functions, we can create +a more portable version of the HTM example in the previous +section that will work on either PowerPC or S/390: +</p> +<div class="smallexample"> +<pre class="smallexample">#include <htmxlintrin.h> + +int num_retries = 10; +TM_buff_type TM_buff; + +while (1) + { + if (__TM_begin (TM_buff) == _HTM_TBEGIN_STARTED) + { + /* Transaction State Initiated. */ + if (is_locked (lock)) + __TM_abort (); + ... transaction code... + __TM_end (); + break; + } + else + { + /* Transaction State Failed. Use locks if the transaction + failure is "persistent" or we've tried too many times. */ + if (num_retries-- <= 0 + || __TM_is_failure_persistent (TM_buff)) + { + acquire_lock (lock); + ... non transactional fallback path... + release_lock (lock); + break; + } + } + } +</pre></div> + +<hr> +<div class="header"> +<p> +Next: <a href="PowerPC-Atomic-Memory-Operation-Functions.html#PowerPC-Atomic-Memory-Operation-Functions" accesskey="n" rel="next">PowerPC Atomic Memory Operation Functions</a>, Previous: <a href="PowerPC-AltiVec_002fVSX-Built_002din-Functions.html#PowerPC-AltiVec_002fVSX-Built_002din-Functions" accesskey="p" rel="previous">PowerPC AltiVec/VSX Built-in Functions</a>, Up: <a href="Target-Builtins.html#Target-Builtins" accesskey="u" rel="up">Target Builtins</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |