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* doc/extend.texi: Document htm builtins.
From-SVN: r205233
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Peter Bergner
Peter Bergner
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@ -1,3 +1,7 @@
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2013-11-21 Peter Bergner <bergner@vnet.ibm.com>
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* doc/extend.texi: Document htm builtins.
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2013-11-21 Jeff Law <law@redhat.com>
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PR tree-optimization/59221
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@ -9218,6 +9218,7 @@ instructions, but allow the compiler to schedule those calls.
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* picoChip Built-in Functions::
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* PowerPC Built-in Functions::
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* PowerPC AltiVec/VSX Built-in Functions::
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* PowerPC Hardware Transactional Memory Built-in Functions::
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* RX Built-in Functions::
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* S/390 System z Built-in Functions::
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* SH Built-in Functions::
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@ -15170,6 +15171,196 @@ The second argument to the @var{__builtin_crypto_vshasigmad} and
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integer that is 0 or 1. The third argument to these builtin functions
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must be a constant integer in the range of 0 to 15.
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@node PowerPC Hardware Transactional Memory Built-in Functions
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@subsection PowerPC Hardware Transactional Memory Built-in Functions
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GCC provides two interfaces for accessing the Hardware Transactional
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Memory (HTM) instructions available on some of the PowerPC family
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of prcoessors (eg, POWER8). The two interfaces come in a low level
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interface, consisting of built-in functions specific to PowerPC and a
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higher level interface consisting of inline functions that are common
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between PowerPC and S/390.
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@subsubsection PowerPC HTM Low Level Built-in Functions
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The following low level built-in functions are available with
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@option{-mhtm} or @option{-mcpu=CPU} where CPU is `power8' or later.
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They all generate the machine instruction that is part of the name.
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The HTM built-ins return true or false depending on their success and
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their arguments match exactly the type and order of the associated
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hardware instruction's operands. Refer to the ISA manual for a
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description of each instruction's operands.
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@smallexample
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unsigned int __builtin_tbegin (unsigned int)
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unsigned int __builtin_tend (unsigned int)
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unsigned int __builtin_tabort (unsigned int)
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unsigned int __builtin_tabortdc (unsigned int, unsigned int, unsigned int)
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unsigned int __builtin_tabortdci (unsigned int, unsigned int, int)
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unsigned int __builtin_tabortwc (unsigned int, unsigned int, unsigned int)
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unsigned int __builtin_tabortwci (unsigned int, unsigned int, int)
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unsigned int __builtin_tcheck (unsigned int)
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unsigned int __builtin_treclaim (unsigned int)
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unsigned int __builtin_trechkpt (void)
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unsigned int __builtin_tsr (unsigned int)
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@end smallexample
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In addition to the above HTM built-ins, we have added built-ins for
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some common extended mnemonics of the HTM instructions:
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@smallexample
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unsigned int __builtin_tendall (void)
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unsigned int __builtin_tresume (void)
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unsigned int __builtin_tsuspend (void)
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@end smallexample
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The following set of built-in functions are available to gain access
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to the HTM specific special purpose registers.
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@smallexample
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unsigned long __builtin_get_texasr (void)
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unsigned long __builtin_get_texasru (void)
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unsigned long __builtin_get_tfhar (void)
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unsigned long __builtin_get_tfiar (void)
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void __builtin_set_texasr (unsigned long);
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void __builtin_set_texasru (unsigned long);
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void __builtin_set_tfhar (unsigned long);
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void __builtin_set_tfiar (unsigned long);
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@end smallexample
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Example usage of these low level built-in functions may look like:
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@smallexample
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#include <htmintrin.h>
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int num_retries = 10;
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while (1)
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@{
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if (__builtin_tbegin (0))
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@{
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/* Transaction State Initiated. */
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if (is_locked (lock))
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__builtin_tabort (0);
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... transaction code...
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__builtin_tend (0);
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break;
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@}
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else
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@{
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/* Transaction State Failed. Use locks if the transaction
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failure is "persistent" or we've tried too many times. */
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if (num_retries-- <= 0
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|| _TEXASRU_FAILURE_PERSISTENT (__builtin_get_texasru ()))
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@{
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acquire_lock (lock);
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... non transactional fallback path...
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release_lock (lock);
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break;
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@}
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@}
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@}
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@end smallexample
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One final built-in function has been added that returns the value of
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the 2-bit Transaction State field of the Machine Status Register (MSR)
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as stored in @code{CR0}.
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@smallexample
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unsigned long __builtin_ttest (void)
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@end smallexample
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This built-in can be used to determine the current transaction state
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using the following code example:
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@smallexample
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#include <htmintrin.h>
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unsigned char tx_state = _HTM_STATE (__builtin_ttest ());
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if (tx_state == _HTM_TRANSACTIONAL)
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@{
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/* Code to use in transactional state. */
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@}
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else if (tx_state == _HTM_NONTRANSACTIONAL)
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@{
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/* Code to use in non-transactional state. */
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@}
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else if (tx_state == _HTM_SUSPENDED)
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@{
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/* Code to use in transaction suspended state. */
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@}
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@end smallexample
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@subsubsection PowerPC HTM High Level Inline Functions
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The following high level HTM interface is made available by including
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@code{<htmxlintrin.h>} and using @option{-mhtm} or @option{-mcpu=CPU}
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where CPU is `power8' or later. This interface is common between PowerPC
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and S/390, allowing users to write one HTM source implementation that
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can be compiled and executed on either system.
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@smallexample
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long __TM_simple_begin (void)
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long __TM_begin (void* const TM_buff)
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long __TM_end (void)
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void __TM_abort (void)
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void __TM_named_abort (unsigned char const code)
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void __TM_resume (void)
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void __TM_suspend (void)
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long __TM_is_user_abort (void* const TM_buff)
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long __TM_is_named_user_abort (void* const TM_buff, unsigned char *code)
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long __TM_is_illegal (void* const TM_buff)
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long __TM_is_footprint_exceeded (void* const TM_buff)
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long __TM_nesting_depth (void* const TM_buff)
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long __TM_is_nested_too_deep(void* const TM_buff)
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long __TM_is_conflict(void* const TM_buff)
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long __TM_is_failure_persistent(void* const TM_buff)
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long __TM_failure_address(void* const TM_buff)
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long long __TM_failure_code(void* const TM_buff)
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@end smallexample
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Using these common set of HTM inline functions, we can create
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a more portable version of the HTM example in the previous
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section that will work on either PowerPC or S/390:
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@smallexample
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#include <htmxlintrin.h>
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int num_retries = 10;
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TM_buff_type TM_buff;
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while (1)
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@{
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if (__TM_begin (TM_buff))
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@{
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/* Transaction State Initiated. */
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if (is_locked (lock))
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__TM_abort ();
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... transaction code...
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__TM_end ();
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break;
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@}
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else
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@{
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/* Transaction State Failed. Use locks if the transaction
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failure is "persistent" or we've tried too many times. */
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if (num_retries-- <= 0
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|| __TM_is_failure_persistent (TM_buff))
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@{
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acquire_lock (lock);
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... non transactional fallback path...
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release_lock (lock);
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break;
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@}
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@}
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@}
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@end smallexample
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@node RX Built-in Functions
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@subsection RX Built-in Functions
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GCC supports some of the RX instructions which cannot be expressed in
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