Volume 4: IA-32 SSE Instruction Reference
4:581
SFENCE: Store Fence
Operation:
while (!(preceding_stores_globally_visible)) wait();
Description:
Weakly ordered memory types can enable higher performance through such techniques
as out-of-order issue, write-combining, and write-collapsing. Memory ordering issues
can arise between a producer and a consumer of data and there are a number of
common usage models which may be affected by weakly ordered stores: (1) library
functions, which use weakly ordered memory to write results (2) compiler-generated
code, which also benefit from writing weakly-ordered results, and (3) hand-written
code. The degree to which a consumer of data knows that the data is weakly ordered
can vary for these cases. As a result, the SFENCE instruction provides a
performance-efficient way of ensuring ordering between routines that produce
weakly-ordered results and routines that consume this data.
SFENCE uses the following ModRM encoding:
Mod (7:6) = 11B
Reg/Opcode (5:3) = 111B
R/M (2:0) = 000B
All other ModRM encodings are defined to be reserved, and use of these encodings risks
incompatibility with future processors.
Numeric Exceptions:
None
Protected Mode Exceptions:
None
Real Address Mode Exceptions:
None
Virtual 8086 Mode Exceptions:
None
Additional Itanium System Environment Exceptions: None
Comments:
SFENCE ignores the value of CR4.OSFXSR. SFENCE will not generate an invalid
exception if CR4.OSFXSR = 0
Opcode
Instruction
Description
0F AE /7
SFENCE
Guarantees that every store instruction that precedes in
program order the store fence instruction is globally visible
before any store instruction which follows the fence is globally
visible.
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 ...