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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.
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...