Power ISA™ Version 2.03 - Power.org

Version 2.03
Extended Mnemonics:
Extended mnemonics for Synchronize:
Extended:
Equivalent to:
sync sync 0
msync sync 0
lwsync sync 1
ptesync sync 2
Except in the sync instruction description in this section,
references to “sync” in Books I - III imply L=0
unless otherwise stated or obvious from context; the
appropriate extended mnemonics are used when other
L values are intended.
Programming Note
Section 1.8 contains a detailed description of how
to modify instructions such that a well-defined
result is obtained.
Programming Note
sync serves as both a basic and an extended mnemonic.
The Assembler will recognize a sync mnemonic
with one operand as the basic form, and a
sync mnemonic with no operand as the extended
form. In the extended form the L operand is omitted
and assumed to be 0.
Programming Note
The sync instruction can be used to ensure that all
stores into a data structure, caused by Store
instructions executed in a “critical section” of a program,
will be performed with respect to another
processor before the store that releases the lock is
performed with respect to that processor; see
Section B.2, “Lock Acquisition and Release, and
Related Techniques” on page 379.
The memory barrier created by a sync instruction
with L=0 or L=1 does not order implicit storage
accesses. The memory barrier created by a sync
instruction with any L value does not order instruction
fetches.
(The memory barrier created by a sync instruction
with L=0 – or L=2; see Book III – appears to
order instruction fetches for instructions preceding
the sync instruction with respect to data accesses
caused by instructions following the sync instruction.
However, this ordering is a consequence of
the first “additional property” of sync with L=0, not
a property of the memory barrier.)
In order to obtain the best performance across the
widest range of implementations, the programmer
should use the sync instruction with L=1, or the
eieio or mbar instruction, if any of these is
sufficient for his needs; otherwise he should use
sync with L=0. sync with L=2 should not be
used by application programs.
Programming Note
The functions provided by sync with L=1 are a
strict subset of those provided by sync with L=0.
(The functions provided by sync with L=2 are a
strict superset of those provided by sync with L=0;
see Book III.)
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Power ISA -- Book II