tbegin machine instruction starting a
non-constrained hardware transaction. If the parameter is non-NULL the
memory area is used to store the transaction diagnostic buffer and
will be passed as first operand to
tbegin. This buffer can be
defined using the
struct __htm_tdb C struct defined in
htmintrin.h and must reside on a double-word boundary. The
second tbegin operand is set to
0xff0c. This enables
save/restore of all GPRs and disables aborts for FPR and AR
manipulations inside the transaction body. The condition code set by
the tbegin instruction is returned as integer value. The tbegin
instruction by definition overwrites the content of all FPRs. The
compiler will generate code which saves and restores the FPRs. For
soft-float code it is recommended to used the
variant. In order to prevent a TDB from being written it is required
to pass a constant zero value as parameter. Passing a zero value
through a variable is not sufficient. Although modifications of
access registers inside the transaction will not trigger an
transaction abort it is not supported to actually modify them. Access
registers do not get saved when entering a transaction. They will have
undefined state when reaching the abort code.
Macros for the possible return codes of tbegin are defined in the
htmintrin.h header file:
tbegin has been executed as part of normal processing. The
transaction body is supposed to be executed.
The transaction was aborted due to an indeterminate condition which might be persistent.
The transaction aborted due to a transient failure. The transaction should be re-executed in that case.
The transaction aborted due to a persistent failure. Re-execution under same circumstances will not be productive.
_HTM_FIRST_USER_ABORT_CODE defined in
specifies the first abort code which can be used for
__builtin_tabort. Values below this threshold are reserved for
struct __htm_tdb defined in
the structure of the transaction diagnostic block as specified in the
Principles of Operation manual chapter 5-91.
__builtin_tbegin but without FPR saves and restores.
Using this variant in code making use of FPRs will leave the FPRs in
undefined state when entering the transaction abort handler code.
In addition to
__builtin_tbegin a loop for transient failures
is generated. If tbegin returns a condition code of 2 the transaction
will be retried as often as specified in the second argument. The
perform processor assist instruction is used to tell the CPU about the
number of fails so far.
__builtin_tbegin_retry but without FPR saves and
restores. Using this variant in code making use of FPRs will leave
the FPRs in undefined state when entering the transaction abort
tbeginc machine instruction starting a constrained
hardware transaction. The second operand is set to
tend machine instruction finishing a transaction
and making the changes visible to other threads. The condition code
generated by tend is returned as integer value.
tabort machine instruction with the specified
abort code. Abort codes from 0 through 255 are reserved and will
result in an error message.
ppa rX,rY,1 machine instruction. Where the
integer parameter is loaded into rX and a value of zero is loaded into
rY. The integer parameter specifies the number of times the
transaction repeatedly aborted.
etnd machine instruction. The current nesting
depth is returned as integer value. For a nesting depth of 0 the code
is not executed as part of an transaction.
ntstg machine instruction. The second argument
is written to the first arguments location. The store operation will
not be rolled-back in case of an transaction abort.