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Volume 4: IA-32 SSE Instruction Reference
PREFETCH: Prefetch
Operation:
fetch (m8);
Description:
If there are no excepting conditions, the prefetch instruction fetches the line containing
the addresses byte to a location in the cache hierarchy specified by a locality hint. If the
line is already present in the cache hierarchy at a level closer to the processor, no data
movement occurs. The bits 5:3 of the ModR/M byte specify locality hints as follows:
• Temporal data(t0) - prefetch data into all cache levels.
• Temporal with respect to first level cache (t1) – prefetch data in all cache levels
except 0th cache level.
• Temporal with respect to second level cache (t2) – prefetch data in all cache levels,
except 0th and 1st cache levels.
• Non-temporal with respect to all cache levels (nta) – prefetch data into
non-temporal cache structure.
Locality hints do not affect the functional behavior of the program. They are
implementation dependent, and can be overloaded or ignored by an implementation.
The prefetch instruction does not cause any exceptions (except for code breakpoints),
does not affect program behavior and may be ignored by the implementation. The
amount of data prefetched is implementation dependent. It will however be a minimum
of 32 bytes. Prefetches to uncacheable memory (UC or WC memory types) will be
ignored. Additional ModRM encodings, besides those specified above, are defined to be
reserved and the use of reserved encodings risks future incompatibility.
Numeric Exceptions:
None
Protected Mode Exceptions:
None
Real Address Mode Exceptions:
None
Virtual 8086 Mode Exceptions:
None
Additional Itanium System Environment Exceptions: None
Comments:
This instruction is merely a hint.If executed, this instruction moves data closer to the
processor in anticipation of future use. The performance of these instructions in
application code can be implementation specific. To achieve maximum speedup, code
tuning might be necessary for each implementation. The non temporal hint also
minimizes pollution of useful cache data.
PREFETCH instructions ignore the value of CR4.OSFXSR. Since they do not affect the
new SSE state, they will not generate an invalid exception if CR4.OSFXSR = 0.
Opcode
Instruction
Description
0F,18,/1
0F,18,/2
0F,18,/3
0F,18,/0
PREFETCHT0 m8
PREFETCHT1 m8
PREFETCHT2 m8
PREFETCHNTA m8
Move data specified by address closer to the processor using
the t0 hint.
Move data specified by address closer to the processor using
the t1 hint.
Move data specified by address closer to the processor using
the t2 hint.
Move data specified by address closer to the processor using
the nta hint.
Содержание ITANIUM ARCHITECTURE
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Страница 270: ...Volume 4 Base IA 32 Instruction Reference 4 263 LFS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 273: ...4 266 Volume 4 Base IA 32 Instruction Reference LGS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 288: ...Volume 4 Base IA 32 Instruction Reference 4 281 LSS Load Full Pointer See entry for LDS LES LFS LGS LSS ...
Страница 352: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Страница 368: ...Volume 4 Base IA 32 Instruction Reference 4 361 SHL SHR Shift Instructions See entry for SAL SAR SHL SHR ...
Страница 373: ...4 366 Volume 4 Base IA 32 Instruction Reference SIDT Store Interrupt Descriptor Table Register See entry for SGDT SIDT ...
Страница 589: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Страница 590: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Страница 591: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Страница 603: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...
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