Volume 3: Instruction Reference
3:165
lfetch
A faulting
lfetch
to an unimplemented address results in an Unimplemented Data
Address fault. A non-faulting
lfetch
to an unimplemented address does not take the
fault and will not issue a prefetch request, but, if specified, will perform a register
post-increment.
Both the non-faulting and the faulting forms of
lfetch
can be used speculatively. The
purpose of raising faults on the faulting form is to allow the operating system to resolve
problems with the address to the extent that it can do so relatively quickly. If problems
with the address cannot be resolved quickly, the OS simply returns to the program, and
forces the data prefetch to be skipped over.
Specifically, if a faulting
lfetch
takes any of the listed faults (other than Illegal
Operation fault), the operating system must handle this fault to the extent that it can
do so relatively quickly and invisibly to the interrupted program. If the fault cannot be
handled quickly or cannot be handled invisibly (e.g., if handling the fault would involve
terminating the program), the OS must return to the interrupted program, skipping
over the data prefetch. This can easily be done by setting the IPSR.ed bit to 1 before
executing an
rfi
to go back to the process, which will allow the
lfetch.fault
to
perform its base register post-increment (if specified), but will suppress any prefetch
request and hence any prefetch-related fault. Note that the OS can easily identify that a
faulting
lfetch
was the cause of the fault by observing that ISR.na is 1, and
ISR.code{3:0} is 4. The one exception to this is the Illegal Operation fault, which can
be caused by an
lfetch.fault
if base register post-increment is specified, and the
base register is outside of the current stack frame, or is GR0. Since this one fault is not
related to the prefetch aspect of
lfetch.fault
, but rather to the base update portion,
Illegal Operation faults on
lfetch.fault
should be handled the same as for any other
instruction.
Table 2-38.
lfhint
Mnemonic Values
lfhint
Mnemonic
Interpretation
none
Temporal locality, level 1
nt1
No temporal locality, level 1
nt2
No temporal locality, level 2
nta
No temporal locality, all levels
Содержание Itanium 9150M
Страница 1: ......
Страница 209: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault...
Страница 301: ...3 292 Volume 3 Pseudo Code Functions Intel Itanium Architecture Software Developer s Manual Rev 2 3...
Страница 405: ...3 396 Volume 3 Resource and Dependency Semantics...
Страница 406: ...3 397 Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index...
Страница 407: ...3 398 Intel Itanium Architecture Software Developer s Manual Rev 2 3...
Страница 419: ...INDEX Index 12 Index for Volumes 1 2 3 and 4...
Страница 420: ......